JTC1/SC22/WG21
N0765
Accredited Standards Committee X3 Doc No: X3J16/95-0165 WG21/N0765
Information Processing Systems Date: July 28, 1995
Operating under the procedures of Project: Programming Language C++
American National Standards Institute Ref Doc:
Reply to: Josee Lajoie
(josee@vnet.ibm.com)
+========================+
| Core WG List of Issues |
+========================+
+-------------------------------------------------+
| Action Items - Papers for the pre-Tokyo mailing |
+-------------------------------------------------+
421: What is a complete object? a sub-object?
460: Definition for the term "variable"
Clark Nelson will provide a paper to clarify the terminology on objects
used in the WP.
XXX: In which situations are complete types required?
Jerry Schwarz will provide a paper to identify when complete types are
required.
526: What is the linkage of names declared in unnamed namespaces?
Mike Anderson will provide a paper to examine what linkage the names in
unnamed namespaces should have and how these names can be used.
XXX: Can main be declared to return an int?
Francis Glassborough will provide a paper to restrict the type of the
function main.
464: Can memcpy be used to copy pointer to members?
Bill Gibbons will provide a paper that will examine if pointer to members
can be categorized as scalar types.
417: Should pointer arithmetic be allowed for pointer-to-abstract classes?
Clark Nelson will provide a paper to describing when pointer arithmetic is
allowed for pointer to abstract classes.
453: Can operator new be called to allocate storage for temporaries, RTTI or
exception handling?
Josee Lajoie will provide a paper to describe how operator new can be used
by an implementation [to allocate static/automatic variables, temporaries,
RTTI data structures, exception handling data structures].
470: Deleting a pointer allocated by a new with placement
Mike Miller will provide a paper to describe when a pointer allocated with
user placement new can be deleted.
78: Linkage specification and calling protocol
Roland Hartinger & Josee Lajoie will provide a paper to propose that it'd
be implementation-defined whether or not extern "C" influences the C++
type system.
+--------+
| Syntax |
+--------+
2.3 [lex.pptoken]:
519: The grammar does not provide a production for pp-number
5.1 [expr.prim]:
512: parsing destructors calls
465: grammar needed to support template function call
466: grammar needed to support ~int()
5.2 [expr.post]:
467: grammar needed to support p->::id
6.8 [stmt.ambig]
132: Consistency between "::" and "Class::" in declarations
424: Must disambiguation update symbol tables?
+-------+
| Core1 |
+-------+
Linkage / ODR
-------------
3.5 [basic.link]:
526: Linkage of names declared in unnamed namespaces
7.5 [dcl.link]:
78: Linkage specification and calling protocol
420: Linkage of C++ entities declared within `extern "C"'
9.6 [class.union]:
505: Must anonymous unions declared in unnamed namespaces also be static?
new / delete
------------
5.3.4 [expr.new]:
453: Can operator new be called to allocate storage for temporaries, RTTI
or exception handling?
5.3.5 [expr.delete]:
340: Which delete operator must be used to delete objects and arrays?
470: Deleting a pointer allocated by a new with placement
Memory Model
------------
3.9 [basic.types]:
192: Should a typedef be defined for the type with strictest alignment?
464: Can memcpy be used to copy pointer to members?
5.3.5 [expr.delete]:
471: When can an implementation change the value of a delete expression?
93: Deleting the "current object" (this) in a member function
Object Model
------------
1.6 [intro.object]:
421: What is a complete object? a sub-object?
3 [basic]:
460: Definition for the term "variable"
5.2.1, 5.2.5, 5.3.1, 5.3.2, 5.7:
417: Should pointer arithmetic be allowed for pointer-to-abstract classes?
5.3.5 [expr.delete]:
416: Can a delete expression be of abstract type?
8.5 [dcl.init]:
476: Can objects with "indeterminate initial value" be referred to?
9.6 [class.union]:
533: Is an anonymous union a type?
10.1 [class.mi]:
529: Can two base class subobjects be allocated at the same address?
10.3 [class.virtual]:
447: When should a class without a final overrider be ill-formed?
Initialization / Destruction
----------------------------
3.6.1 [basic.start.main]:
462: Calling exit from a destructor for a global variable
484: When must objects of static storage duration be destroyed wrt to
calls to functions registered with atexit?
3.6.2 [basic.start.init]:
429: Order of initialization of reference variables
527: When must the initialization of nonlocal objects take place?
3.6.3 [basic.start.term]:
430: Order of destruction of local static variables
5.2.2 [expr.call]:
535: Does the initialization of a parameter take place in the caller or in
the callee?
6.7 [stmt.dcl]:
524: Exactly when are objects of automatic storage duration destroyed?
9.6 [class.union]:
105: How can static members which are anon unions be initialized?
12.4 [class.dtor]:
293: Clarify the meaning of y.~Y
12.6 [class.init]:
138: When are default ctor default args evaluated for array elements?
12.6.2 [class.base.init]:
478: Can a union constructor initialize multiple members?
534: Can the members of an anonymous union be named in a ctor-initializer?
Special Member Functions
------------------------
11.1 [class.access.spec]:
22: Must implementations respect access restrictions?
11.2 [class.access.base]:
284: Access to base class ctor/dtor
12.1 [class.ctor]:
379: Invoking member functions which are "not inherited"
12.8 [class.copy]:
95: Volatility, copy constructors, and assignment operators
+-------+
| Core2 |
+-------+
Name Look Up
------------
5.1 [expr.prim]:
433: What is the syntax for explicit destructor calls?
5.2.4 [expr.ref]:
452a: How does name look up work after . or -> for namespace names or
template names?
7.3.2 [namespace.alias]:
474: Lookup of namespace names in alias declarations
7.3.4 [namespace.udir]:
475: Lookup of namespace names in using directives
10[class.derived]:
441: In which scope is the base class clause looked up?
10.1 [class.mi]:
446: Can explicit qualification be used for base class navigation?
11.4 [class.friend]:
448: Can '::' be used to declare global functions as friends?
Lexical conventions
-------------------
2.9.3 [lex.fcon]:
506: Is a program containing a non-representable floating point constant
ill-formed?
Types / Classes / Unions
------------------------
5.3.3 [expr.sizeof]
528: can sizeof be applied to a reference type?
7 [dcl.dcl]:
213: Should vacuous type declarations be prohibited?
7.1.5 [dcl.type]:
116: Is "const class X { };" legal?
7.2 [dcl.enum]:
503: Better semantics of bitfields of enumeration type needed
9.1 [class.name]:
252: Where can the definition of an incomplete class object appear?
9.2 [class.mem]:
479: How can typedefs be used to declared member functions?
9.6 [class.union]:
266: Access specifiers in union member list
Declarators
-----------
8.3.4 [dcl.array]:
457: What is the linkage of a cv-qualified array?
8.3.5 [dcl.fct]:
482: Are cv-qualifiers allowed in a typedef for a function type?
8.3.6 [dcl.fct.default] :
530: Can default arguments appear in out-of-line member function
definitions?
531: Is a default argument a context that requires a value?
9.7 [class.bit]:
47: enum bitfields - can they be declared with < bits than required?
267: What does "Nor are there any references to bitfields" mean?
458: When is an enum bitfield signed / unsigned?
Constant Expressions
--------------------
5.19 [expr.const]:
537: Can the implementation accept other constant expressions?
Type Conversions / Function Overload Resolution
-----------------------------------------------
4.9 [conv.fpint]:
455: Should implicit floating->integral conversions be deprecated?
4.13 [conv.bool]:
523: Conversions from pointer to integral type
5.2.9 [expr.reinterpret.cast]:
486: Can a value of enumeration type be converted to pointer type?
487: Conversions to pointer to member functions need to be changed to
allow covariant return types
538: Are user-defined conversions invoked as the result of a
reinterpret_cast?
5.9 [expr.rel]:
493: Better description of the cv-qualification for the result of a
relational operator needed
513: Are pointer conversions implementation-defined or unspecified?
5.16 [expr.cond]:
472: lvalue-> rvalue transformation for the operands of the conditional
operator needs better description
496: The cv-qualification of the result of the conditional operator needs
better description
497: The conversion applied to operands of the conditional operator of
class type needs to be better described
12.3.2 [class.conv.fct]:
347: Limitations on declarations of user-defined type-conversions
13.2.1.1.1 [over.call.func]:
451: Description of a call to a member function through a pointer to
member is missing
Access Specification & Friends
------------------------------
11.3 [class.access.dcl]:
388: Access Declarations and qualified ids
11.4 [class.friend]:
515: How can friend classes use private and protected names?
532: Is a complete class definition allowed in a friend declaration
+--------+
| Core 3 |
+--------+
Pointer to Members
------------------
5.5 [expr.mptr.oper]:
488: Can a pointer to a mutable member be used to modify a const class
object?
RTTI
----
5.2.6 [expr.dynamic.cast]:
468: How does dynamic_cast to void* work for non-polymorphic types?
5.2.7 [expr.typeid]:
483: What does a compiler know about type_info if the header isn't
included?
Exception Handling
------------------
15.3 [except.handle]:
539: Can one throw a pointer-to-member to a base class and catch it with a
handler taking a pointer to a derived class?
540: How does name look up proceed in a function-try-block?
541: Is a function-try-block allowed for the function main?
542: What exception can a reference to a pointer to base catch?
+----------------+
| Core Editorial |
+----------------+
3.2 [basic.def.odr]:
427: When is a diagnostic required when a member function used is not
defined?
3.3.1 [basic.scope.local]:
509: The controlling expression of a do statement cannot declare anything
3.4 [class.scope]:
510: Function overloads may come from different scopes
3.6.3 [basic.start.term]:
520: Order of object destruction and atexit
521: abort and destruction of objects of automatic storage duration
3.9 [basic.types]:
511: The requirements on alignment restrictions are incorrect
522: numeric_limits and fundamental types
3.10 [basic.lval]:
431: Are void expressions ever lvalues?
5.3.5 [expr.delete]:
426: Deleting arrays if dynamic type differs from type of delete expression
9.7 [class.bit]:
525: Implementation specific mapping of bitfields
5.18 [expr.comma]:
499: When are temporaries destroyed when created by the left expression of
the comma operator?
6.7 [stmt.dcl]:
500: Can one jump over the definition of a variable of enumeration type?
8.3.2 [dcl.ref]:
456: What is the linkage of a cv-qualified reference to T?
9 [class]:
514: The list of member types a POD class cannot have is not complete
9.8 [class.nest]:
68: How do access control apply to members of nested classes in the
definition of the owning class?
10.1 [class.mi]:
11: How do retrictions on member mapping apply with multiple inheritance?
442: Can a class have a direct and an indirect base of the same type?
12.2 [class.temporary]:
477: When can an implementation create temporaries?
507: Must a temporary initializing an object be destroyed _as soon as_ it
has been copied?
509: How does "destroy in reverse order of creation" work for temporaries
bound to references vs temporaries destroyed at the end of the
initialization?
12.4 [class.dtor]:
485: Order of destruction of base classes and members
508: When is a destructor implicitly-defined?
+-------------------------------------------------------------+
| Closed Issues - Resolutions adopted at the Monterey meeting |
+-------------------------------------------------------------+
2.9.2[lex.ccon]:
459: Can octal sequences have more than 3 characters?
3.2 [basic.def.odr]:
113: Can inline functions refer to static global variables?
428: ODR for block scope extern declarations
3.5 [basic.link]:
461: Do namespace names have linkage?
3.7.3.1 [basic.stc.dynamic.allocation]:
463: Can operator new/delete with placement be declared in a named
namespace?
5.3.4 [expr.new]:
435: Can reference types be newed?
436: What is the type of a new expression allocating an array?
469: Better name lookup rules for operator new needed
5.6 [expr.mul]:
489: Can the operands of the multiplicative operators be of enumeration
type?
5.7 [expr.add]:
490: Can the operands of the additive operators be of enumeration type?
5.8 [expr.shift]:
491: Can the operands of the shift operators be of enumeration type?
5.9 [expr.rel]:
492: Can the operands of the relational operators be of enumeration type?
5.10 [expr.eq]:
481: What are the semantics for pointer to member comparison?
5.11 [expr.bit.and], 5.12 [expr.xor], 5.13 [expr.or]:
494: Can the operands of the bitwise operators be of enumeration type?
5.16 [expr.cond]:
495: Can the operands of the conditional operator be of enumeration type?
5.17 [expr.ass]:
498: Can the operands of the assignment operator be of enumeration type?
7.1.1 [dcl.stc]:
437: How do extern declarations link with previous declarations?
473: linkage of local static variables needs to be better described
7.1.2 [dcl.fct.spec]:
454: Can two inline functions call one another?
7.1.3 [dcl.typedef]:
502: What is the linkage name of unnamed enum types introduced by a
typedef?
7.5 [dcl.link]:
486: What is the effect of multiple linkage declarations?
8.3.2 [dcl.ref]:
514: The list of member types a POD class cannot have is not complete
8.3.5 [dcl.fct]:
439: Are there any restrictions on the parameter before the ellipsis?
9.6 [class.union]:
335: Can unions contain reference members?
9.8 [class.nest]:
27: What is the access of nested class types declared multiple times
11.5 [class.protected]:
449: restriction on protected member access should not apply to types,
static members, and member constants
12.2 [class.temporary]:
516: What is the lifetime of "helping" temporaries?
12.5 [class.free]:
450: How is a class operator new/delete looked up?
12.6.2 [class.base.init]:
359: Timing of Evaluations in Base and Member Initializations
13.6 [over.built]:
517: Candidate operator functions for built-in operators do not cover the
type bool appropriately
518: Candidate operator function for built-in operator= for pointer to
members is missing
=============================================================================
Chapter 1 - Introduction
--------------------------
Work Group: Core
Issue Number: 421
Title: What is a complete object? a sub-object?
Section: 1.6 [intro.object] Object Model
Status: active
Description:
There appears to have been a substantive change in the definition of
"sub-object" and "complete object" in the Working Paper.
Sub-objects used to include only objects representing base classes.
A complete object used to include all objects (even members) that
aren't base class objects of other objects. Now sub-objects include
members, and complete objects exclude members. This introduces a
number of unfortunate side-effects in the standard where the
definitions are used.
3.8 [basic.life] p7:
"-- the original object was a complete object of type T and the new
object is a complete object of type T (that is, they are not base
class subobjects)."
5.2.6 [expr.dynamic.cast] p7:
"If T is ``pointer to cv void'', then the result is a pointer to the
complete object pointed to by v. ...
If, in the complete object pointed (referred) to by v, v points
(refers) to an public base class sub-object of a T object, ...
Otherwise, if the type of the complete object has an unambiguous
public base class of type T, the result is a pointer (reference) to
the T sub-object of the complete object."
5.2.7 [expr.typeid] p3
"If the expression is a reference to a polymorphic type, the
type_info for the complete object referred to is the result. ...
... Otherwise, the result of the typeid expression is the value that
represents the type of the complete object to which the pointer
points."
10 [derived] p3
"3 The order in which the base class subobjects are allocated in the
complete object is unspecified."
5 A base class subobject might have a layout different from the
layout of a complete object of the same type. A base class
subobject might have a polymorphic behavior of a complete object
of the same type."
10.1 [class.mi] p4
"For each distinct occurrence of a nonvirtual base class in the
class lattice of the most derived class, the complete object shall
contain a corresponding distinct base class subobject of that type.
For each distinct base class that is specified virtual, the
complete object shall contain a single base class subobject of that
type."
12.7 [class.cdtor] p3:
"3 When a virtual function is called directly or indirectly from a
constructor (including from its ctor-initializer ) or from a
destructor, the function called is the one defined in the
constructor or destructor's own class or in one of its bases, but
not a function overriding it in a class derived from the
constructor or destructor's class or overriding it in one of the
other base classes of the complete object."
...
5 When a dynamic_cast is used in a constructor (including in its
ctor-initializer) or in a destructor, or used in a function
called (directly or indirectly) from a constructor or destructor,
if the operand of the dynamic_cast refers to the object under
construction or destruction, this object is considered to be a
complete object that has the type of the constructor or
destructor's class.
Proposed Resolution:
We need to introduce another term in the WP to describe objects that
are either member subobject or complete objects.
It was suggested before that the term "nonbase" object could be used.
Resolution:
Clark will provide a paper for the Tokyo meeting (November 1995).
Requestor: Neal M Gafter <gafter@mri.com>
Owner: Clark Nelson (Object Model)
Emails: edit-195, edit-196
Papers:
=============================================================================
Chapter 2 - Lexical Conventions
---------------------------------
Work Group: Core
Issue Number: 519
Title: The grammar does not provide a production for pp-number
Section: 2.3 [lex.pptoken] Preprocessing tokens
Status: active
Description:
The grammar does not provide a production for pp-number.
Resolution:
Requestor: Sean Corfield
Owner: Anthony Scian (Syntax)
Emails:
Papers:
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Work Group: Core
Issue Number: 459
Title: Can octal sequences have more than 3 characters?
Section: 2.9.2 [lex.ccon] Character literals
Status: closed
Description:
2.9.2 p4 says:
"There is no limit to the number of digits in either (octal or
hexadecimal) sequences."
In C, only 3 characters are allowed in octal sequences.
Should C++ and C differ in this case?
And if yes, appendix C should be updated.
Resolution:
See Monterey motion 2a.
Requestor:
Owner: Tom Plum
Emails:
Papers:
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Work Group: Core
Issue Number: 506
Title: Is a program containing a non-representable floating point
constant ill-formed?
Section: 2.9.3 [lex.fcon]
Status: active
Description:
2.9.1 [lex.icon] p3 says:
"A program is ill-formed if it contains an integer literal that
cannot be represented by any of the allowed types."
For consistency with 2.9.1, shouldn't a program containing a
non-representable floating point constant be ill-formed? (if the
exponent is too large, for example?)
Resolution:
Requestor: Erwin Unruh
Owner: Tom Plum
Emails:
Papers:
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
=============================================================================
Chapter 3 - Basic Concepts
----------------------------
Work Group: Core
Issue Number: 460
Title: Definition for the term "variable"
Section: 3 [basic] Basic concepts
Status: active
Description:
Editorial Box 5:
The definition for the term variable is needed.
Proposal:
"A variable is introduced by an object's declaration and the
variable's name denotes the object."
Resolution:
Clark will provide a paper for the Tokyo meeting (November 1995).
Requestor:
Owner: Clark Nelson (Object Model)
Emails:
Papers:
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Work Group: Core
Issue Number: 113
Title: Can inline functions refer to static global variables?
Section: 3.2 [basic.def.odr] One Definition Rule
Status: closed
Description:
7.1.2 p3 says:
"An inline member function must have exactly the same definition in
every compilation unit in which it appears."
Can an inline function accessed a file static variable?
How can it do so and respect the statement describe above?
Proposed Resolution:
[JL:] An inline member function must have the same definition in
different compilation units. Therefore it cannot access a file
static variable.
However, the ODR rule needs to be better defined and the Core WG is
working on this.
Resolution:
See Monterey motion 5.
Requestor: Small issues / Core Language WG discussions
Owner: Josee Lajoie (ODR)
Emails:
Papers:
94-0009/N0369
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Work Group: Core
Issue Number: 427
Title: When is a diagnostic required when a member function used is
not defined?
Section: 3.2 [basic.def.odr] One Definition Rule
Status: editorial
Description:
p2.4
"If a non-virtual function is not defined, a diagnostic is
required only if an attempt is actually made to call the
function."
Isn't it too severe to force an implementation to issue a
diagnostic in this case? Shouldn't it be "no-diagnostic required"?
Possible rewording:
If a non-pure virtual function is not defined and it is neither
called nor used to form a pointer to member, no diagnostic is
required.
Resolution:
Core 1 decided at the Monterey meeting that this is an editorial
issue.
Requestor: Josee Lajoie
Owner: Josee Lajoie (ODR)
Emails:
Papers:
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Work Group: Core
Issue Number: 428
Title: ODR for block scope extern declarations
Section: 3.2 [basic.def.odr] One Definition Rule
Status: closed
Description:
Is a diagnostic required if 2 extern block scope declarations
declare the same name with different attributes, i.e.:
void f() {
extern int a[5];
}
void g() {
extern int a[7];
}
Resolution:
3.5 [basic.link] paragraph 9 already requires this.
Requestor: Josee Lajoie
Owner: Josee Lajoie (ODR)
Emails:
Papers:
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Work Group: Core
Issue Number: 509
Title: The controlling expression of a do statement cannot declare
anything
Section: 3.3.1 [basic.scope.local] Local Scope
Status: editorial
Description:
3.3.1p5 says:
"Names declared in the outermost block of the controlled statement
of a do statement shall not be redeclared in the controlling
expression."
A 'do' does not have a 'condition', so the controlling expression
cannot declare anything.
Resolution:
Delete paragraph 5.
Requestor: Erwin Unruh
Owner: Josee Lajoie (Core Editorial)
Emails:
Papers:
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Work Group: Core
Issue Number: 510
Title: Function overloads may come from different scopes
Section: 3.4 [class.scope] Name look up
Status: editorial?
Description:
3.4p2 says:
"Name look up may associate more than one declaration with a name if
it finds the name to be a function name; in this case, all
declarations shall be found in the same scope..."
This is incorrect since overloading across namespaces is allowed.
Proposal:
Replace the sentence above with:
"Name look up may associate more than one declaration with a name if
it finds the name to be a function name; in this case, all
declarations found will be from the same scope, either explicitly
declared in that scope or visible in that scope because of using
directives (7.3.4)."
Resolution:
I would like to make this an editorial issue. Would there be any
objection?
Requestor: Erwin Unruh
Owner: Steve Adamczyk (Name look up)
Emails:
Papers:
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Work Group: Core
Issue Number: 461
Title: Do namespace names have linkage?
Section: 3.5 [basic.link] Program and linkage
Status: closed
Description:
3.5 does not discuss namespace names.
Do namespace names have linkage?
Proposed Solution:
Yes, namespaces have external linkage.
This ensures that
// ----- File 1 -----
struct A {
void f();
};
// ----- File 2 -----
namespace A {
void f();
}
In this example, the class A and the namespace A both have external
linkage. When files 1 and 2 are linked together, the name A does not
refer to the same entity in both files. The program violates the ODR
and may result in undefined behavior.
Proposal:
Add a bullet to paragraph 4:
-- a namespace (7.3)
Resolution:
See Monterey motion 8.
Also see 95-0147R1/N0747R1.
Requestor: Kate Burleson
Owner: Josee Lajoie (Linkage)
Emails: core-5555
Papers:
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Work Group: Core
Issue Number: 526
Title: What is the linkage of names declared in unnamed namespaces?
Section: 3.5 [basic.link] Program and linkage
Status: active
Description:
What is the linkage of names declared in an unnamed namespace?
internal linkage?
Internal linkage applies to variables and functions.
What would the status of a type definition be in an unnamed
namespace?
No linkage?
Can it be used to declare a function with external linkage?
Can it be used to instantiate a template?
namespace {
class A { /* ... */ };
}
extern void f(A&); // error?
template <class T> class X { /* ... */ };
X<A> x; // error?
If A does not have external linkage, then the two declarations are
probably errors. If it does have external linkage, then the two
declarations are legal (and the implementation probably has to worry
about name mangling).
At the Monterey meeting, Mike Anderson promised to present a paper
at the Tokyo meeting with a proposed resolution.
Resolution:
Requestor: Mike Anderson
Owner: Josee Lajoie (Linkage)
Emails:
core-5905 and following messages.
Papers:
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Work Group: Core
Issue Number: 462
Title: calling exit from a destructor for a global variable
Section: 3.6.1 [basic.start.main] Main function
Status: active
Description:
3.6.1 p4:
"Calling the function [exit] declared in <cstdlib> terminates the
program without leaving the current block and hence without
destroying any objects with automatic storage duration."
What happens if exit is called from the destructor for a global
variable?
The global destructor will be called again for the same object when
exit destroys the global objects.
[ JL Note: ]
Related question:
What if a global destructor throws an exception and the user-defined
terminate routine calls exit?
Proposal:
At the Thursday session in Monterey, Core 1 came to the following
agreement:
The draft should say that calling 'exit' from a destructor results
in undefined behavior.
Add to 3.6.1 [basic.start.main] paragraph 4:
"If 'exit' is called during the destruction at block exit of
objects with automatic storage duration or during the
destruction at the end of the program of objects with static
storage duration, the program results in undefined-behavior."
This will be presented for a vote in Tokyo.
Resolution:
Requestor: Simon Tooke
Owner: Josee Lajoie (Initialization/Destruction)
Emails:
Papers:
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Work Group: Core
Issue Number: 484
Title: When must objects of static storage duration be destroyed wrt
to calls to functions registered with atexit?
Section: 3.6.1 [basic.start.main] Main function
Status: active
Description:
The WP (28 April 1995 printing), Section 18.3.2 states that static
objects are destroyed in the reverse order of their construction
after all functions registered via atexit() are called. Yet Section
6.7 Paragraph 5 seems to contradict this statement by requiring that
the destructor of a local object with static storage duration be
called either immediately before or as part of the calls of the
atexit() functions. In particular, 6.7 allows destruction before
the call of atexit functions yet 18.3.2 requires it follow such
functions.
Jerry Schwarz also points out:
A) What is the correct thing to happen if atexit is called
during construction of a static object?
B) What should happen if a static object is constructed
during a call to a function that was registered via atexit?
void f() {
static T t(1);
}
void g() {
static T u(2);
}
main() {
atexit(f);
atexit(g);
f(); // ensures 't' is constructed, 'u' is not yet
exit(0); // now what? calls 'g' and then 'f'
// two questions arise:
// 1) is 'u' destroyed?
// (it wasn't constructed prior to the atexit function
// calls)
// 2) has 't' been destroyed prior to calling 'f' again?
}
C) What if exit is called from the initialization of a static before
main even begins to run?
Resolution:
Requestor: lijewski@roguewave.com
Owner: Josee Lajoie (Initialization/Destruction)
Emails:
core-5596
Papers:
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Work Group: Core
Issue Number: 429
Title: Order of initialization of reference variables
Section: 3.6.2 [basic.start.init] Initialization of non-local objects
Status: active
Description:
Is the following initialization of "r" performed "statically" (that
is, at link time) or "dynamicaly" (that is, at its turn among
dynamically initialized nonlocal objects in the translation unit)?
extern int x;
int &r = x;
Resolution:
Requestor: Neal Gafter
Owner: Josee Lajoie (Initialization/Destruction)
Emails:
Papers:
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Work Group: Core
Issue Number: 527
Title: When must the initialization of nonlocal objects take place?
Section: 3.6.2 [basic.start.init] Initialization of non-local objects
Status: active
Description:
3.6.2[basic.start.init] paragraph 1 says:
"The initialization of nonlocal objects with static storage
duration defined in a translation unit shall be done before the
first use of any function or object defined in that translation
unit."
What does 'use' mean here?
It was suggested that the above wording be clarified as follows:
Proposal:
"The initialization of nonlocal objects with static storage duration
defined in a translation unit shall be done before the first use
(where a use follows the invocation of 'main' and does not take
into account any usage within initializations for objects with
static storage duration) of any function or object defined in that
translation unit."
Resolution:
Requestor: John Max Skaller
Owner:
Emails:
core-5672
Papers:
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Work Group: Core
Issue Number: 430
Title: Order of destruction of local static variables
Section: 3.6.3 [basic.start.term] Termination
6.7 [stmt.dcl] Declaration statement
Status: active
Description:
3.6.3 says static objects are destroy in reverse order of
intialization.
6.7 says destruction order is unspecified.
Which one is right?
Resolution:
Requestor: Mike Ball
Owner: Josee Lajoie (Initialization/Destruction)
Emails: core-4989
Papers:
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Work Group: Core
Issue Number: 520
Title: Order of object destruction and atexit
Section: 3.6.3 [basic.start.term] Termination
Status: editorial?
Description:
3.6.3 p1 says:
"If atexit is to be called, the implementation shall not destroy
objects initialized before an atexit call until after the function
specified in the atexit() call has been called."
Does this sentence refer to all objects (i.e. of automatic and static
storage duration) or only to global objects (i.e. of static storage
duration).
Proposed Resolution:
Change the sentence above to say:
"... the implementation shall not destroy global objects initialized
before an atexit call until ..."
Resolution:
I would like to make this an editorial issue. Would there be any
objection?
Requestor: Sean Corfield
Owner: Josee Lajoie (Initialization/Destruction)
Emails:
Papers:
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Work Group: Core
Issue Number: 521
Title: abort and destruction of objects of automatic storage
duration
Section: 3.6.3 [basic.start.term] Termination
Status: editorial
Description:
3.6.3p3 says:
"Calling the function [abort] terminates the program without
executing destructor for static objects and without calling the
functions passed to atexit()."
This doesn't make it clear that destructors for local objects are not
called either.
Proposed Resolution:
Change the sentence above to say:
"Calling the function [abort] terminates the program without calling
the destructor for objects of automatic and static storage duration
and without calling the functions passed to atexit()."
Resolution:
Core 1 decided at the Monterey meeting that this is an editorial
issue.
Requestor: Sean Corfield
Owner: Josee Lajoie (Initialization/Destruction)
Emails:
Papers:
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Work Group: Core Language
Issue Number: 463
Title: Can operator new/delete with placement be declared in a named
namespace?
Section: 3.7.3.1 [basic.stc.dynamic.allocation]
Status: closed
Description:
3.7.3.1 p1 says:
"Allocation functions can be static class member functions or global
functions."
However, the library only requires that:
::operator new(size_t)
::operator new[](size_t)
::operator delete(void*)
::operator delete[](void*)
be either declared in class scope or in global scope.
Does the sentence above apply to operator new/delete with placement
as well? Or can operator new/delete with placement be declared in
a namespace scope other than global scope?
Proposal:
Yes, operator new/delete with placement can be declared in a named
namespace.
Resolution:
See Monterey motion 9.
Also see paper 95-0148R1/N0748R1.
Requestor:
Owner: Josee Lajoie (new/delete)
Emails:
Papers:
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Work Group: Core
Issue Number: 192
Title: Should a typedef be defined for the type with strictest
alignment?
Section: 3.9 [basic.types] Types
Status: active
Description:
It would be useful if <new.h> provided a typedef for a name such as
__strict_align_t , to describe a type whose alignment is the
strictest required in this environment. It is otherwise hard to
write a portable overloaded new operator. Faking it, by defining
a union of several "typical" types, is not really portable, and its
quiet mode of failure might be extremely puzzling, because the
program would run just fine most of the time in most environments,
except that in some unusual environment the program would
occasionally produce an alignment error.
As WG14 and X3J11 have found out, some compilers add an alignment
requirement for structures embedded inside structures, one which is
even more restrictive than the scalar types!
There are no real-world guarantees about alignment, unless the
committee imposes them.
ALTERNATIVE: The committee could prescribe specific requirements for
alignment. E.g., in any conforming environment, no object may have
an alignment requirement more restrictive than this specific type:
struct _strict_align_t { struct { long n; double d; }; };
92/12/07 NOTE: To allow the writing of portable allocators, it may
also be necessary to define an __align_pointer(p) function, which
returns the nearest pointer (address) value which is aligned on the
strictest boundary and is greater than or equal to the pointer value
p .
Resolution:
Requestor: Tom Plum / Dan Saks
Owner: Josee Lajoie (Memory Model)
Emails:
Papers:
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Work Group: Core
Issue Number: 511
Title: The requirements on alignment restrictions are incorrect
Section: 3.9 [basic.types] Types
Status: editorial
Description:
3.9p6 says:
"... an object is allocated at an address that is divisible by the
alignment of its object type."
Alignment restrictions are implementation-defined. The restriction
may be another then divisibility of the pointer. Beside, divisibility
is not defined for pointers. The restriction should instead express
'the requirements of pointers that must point to objects of such
type'.
Replace the sentence above with:
"... an object is allocated at an address that meets the alignment
requirements for its type."
Resolution:
Core 1 decided at the Monterey meeting that this is an editorial
issue.
Requestor: Erwin Unruh
Owner: Josee Lajoie (Memory Model)
Emails:
Papers:
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Work Group: Core
Issue Number: 464
Title: Can memcpy be used to copy pointer to members?
Section: 3.9 [basic.types] Types
Status: active
Description:
3.9 p3 says:
"For any scalar type T, if two pointers to T point to distinct T
objects obj1 and obj2, if the value of obj1 is copied into obj2,
using the memcpy library function, obj2 shall subsequently hold the
same value as obj1."
Shouldn't this also be valid if T is a pointer to member type?
class A { void f(int); };
typedef (A::*PM)(int);
{
A a;
PM p = A::f;
PM q;
memcpy(&q, &p, sizeof(PM));
(a.*q)(0);
}
Proposal:
Change the sentence above to say:
"For any scalar type or pointer to member type T, ..."
Resolution:
Bill Gibbons will provide a paper for the Tokyo meeting (November
1995), paper that investigates the possibility of making pointer to
members scalar types.
Requestor: Nathan Myers
Owner: Bill Gibbons (Memory Model)
Emails:
Papers:
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Work Group: Core
Issue Number: 522
Title: numeric_limits and fundamental types
Section: 3.9.1 [basic.fundamental] Fundamental types
Status: editorial
Description:
3.9.1p1 says:
"Specializations of the standard template numeric_limits (18.2) shall
specify the largest and smallest values of each for an
implementation."
Not true for all fundamental types.
void, bool, enumeration types are not included.
Resolution:
Core 1 decided at the Monterey meeting that this is an editorial
issue.
Requestor: Sean Corfield
Owner: Josee Lajoie (Memory Model)
Emails:
Papers:
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Work Group: Core Language
Issue Number: 431
Title: Are void expressions ever lvalues?
Section: 3.10 [basic.lval] Lvalues and rvalues
Status: editorial
Description:
In ISO C, expressions having type void are never considered to be
lvalues. Thus, the following code violates a constraint of the C
standard, and conforming implementations are required to issue a
diagnostic:
void *vp;
void foo () {
&*vp; /* constraint violation */
}
Are expression having THE void type and/or expressions having some
qualified void type every considered to be lvalues in C++?
Resolution:
Core 2 indicated that this was already clear in the WP.
I however believe that 3.10 paragraph 8 could be made clearer.
Requestor: Ron Guilmette
Owner: Steve Adamczyk (Lvalues)
Emails:
Papers:
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
=============================================================================
Chapter 4 - Standard Conversions
----------------------------------
Work Group: Core
Issue Number: 455
Title: Should implicit floating->integral conversions be deprecated?
Section: 4.9 [conv.fpint] Floating-integral conversions
Status: active
Description:
Requestor: Bjarne Stroustrup
Owner: Steve Adamczyk (Type Conversions)
Emails:
core-4757
Papers:
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Work Group: Core
Issue Number: 523
Title: Conversions from pointer to integral type
Section: 4.13 [conv.bool] Boolean conversions
Status: active
Description:
It is not clear, reading the rules in 4.5 [conv.prom] and 4.13
that the following conversion is disallowed:
int i;
char *cp;
i = cp; // converts char* -> bool -> int ???
Requestor: Sean Corfield
Owner: Steve Adamczyk (Type Conversions)
Emails:
Papers:
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
=============================================================================
Chapter 5 - Expressions
-------------------------
Work Group: Core
Issue Number: 512
Title: parsing destructors calls
Section: 5.1 [expr.prim] Primary expressions
Status: active
Description:
5.1p7 says:
"A class-name prefix by ~ denotes a destructor."
There is a syntactic ambiguity on the usage of a destructor.
The code '~X();' in the scope of a member function of class X can be
interpreted as an explicit destructor call using the implicit this
pointer. The other interpretation is the unary operator ~ applied
to a function like cast.
Resolution:
Requestor: Erwin Unruh
Owner: Anthony Scian (Syntax)
Emails:
Papers:
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Work Group: Core
Issue Number: 433
Title: What is the syntax for explicit destructor calls?
Section: 5.1 [expr.prim] Primary expressions
12.4 [class.dtor] Destructors
Status: active
Description:
Question 1:
p10 says:
The notation for explicit call of a destructor may be used for any
simple type name. For example:
int* p;
p->int::~int();
Must the destructor name be a qualified-id or can it be written as:
p->~int();
?
Question 2:
Can a typedef name be used following the ~, and if so, what are the
lookup rules?
struct A {
~A(){}
};
typedef class A B;
int main()
{
A* ap;
ap->A::~A(); // OK
ap->B::~B(); // cfront/Borland OK, IBM/Microsoft/EDG error
ap->A::~B(); // cfront OK, Borland/IBM/Microsoft/EDG error
ap->~B(); // OK?
}
This issue concerns the lookup of explicit destructor calls for
nonclass types as well.
typedef int I;
typedef int I2;
int* i;
i->int::~int();
i->I::~I();
i->int::~I();
i->I::~int();
i->I::~I2();
Which of these are well formed?
Resolution:
Requestor: John H. Spicer
Owner: Steve Adamczyk (Name Lookup)
Emails:
Papers:
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Work Group: Core Language
Issue Number: 465
Title: grammar needed to support template function call
Section: 5.1 [expr.prim] Primary expression
Status: active
Description:
"id-expression" does not allow the syntax
f<arg>
needed for a call to a template function using explicit arguments.
Possible solution:
Add template-function-id (i.e. production for f<>) to the list of
unqualified-ids:
unqualified-id:
...
template-function-id
Resolution:
Requestor:
Owner: Anthony Scian (Syntax)
Emails:
Papers:
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Work Group: Core Language
Issue Number: 466
Title: grammar needed to support ~int()
Section: 5.1 [expr.prim] Primary expression
Status: active
Description:
The grammar does not allow for explicit destructor calls for
built-in types:
int* pi;
pi->~int();
Possible solution:
unqualified-id:
...
~enum-name
~typedef-name
~simple-type-specifier
Resolution:
Requestor:
Owner: Anthony Scian (Syntax)
Emails:
Papers:
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Work Group: Core Language
Issue Number: 467
Title: grammar needed to support p->::id
Section: 5.2 [expr.post] Postfix expressions
Status: active
Description:
Resolution:
Possible solution:
Change
postfix-expression:
postfix-expression . template(opt) id-expression
postfix-expression -> template(opt) id-expression
to
postfix-expression:
postfix-expression . ::(opt) template(opt) id-expression
postfix-expression -> ::(opt) template(opt) id-expression
Requestor:
Owner: Anthony Scian (Syntax)
Emails:
Papers:
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Work Group: Core Language
Issue Number: 417
Title: Should pointer arithmetic be allowed for pointer-to-abstract
classes?
Section: 5.2.1, 5.2.5, 5.3.1, 5.3.2, 5.7
Status: active
Description:
Should pointer arithmetic and/or the sizeof operator be allowed for
operands whose type is some pointer-to-abstract type?
Note that if it is the committee's judgement to effect such
restriction, these restrictions would have to be reflected in
working paper sections 5.2.1, 5.2.5, 5.3.1, 5.3.2, and 5.7.
Resolution:
Clark will provide a paper for the Tokyo meeting (November 1995).
Requestor: Ron Guilmette
Owner: Clark Nelson (Object Model)
Emails:
Papers:
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Work Group: Core
Issue Number: 535
Title: Does the initialization of a parameter take place in the
caller or in the callee?
Section: 5.2.2 [expr.call]
Status: active
Description:
The DWP says, (5.2.2, P3)
"When a function is called, each parameter(8.3.5) shall be
initialized with its corresponding argument. Standard and
user-defined conversions shall be performed"
And in (P9) it says
"All side effects of argument expressions take effect before the
function is entered".
The questions are
1. Is the initialization of the parameter part of entering the
function, or is it part of evaluating the argument?
2. Is the application of a conversion part of evaluating the
argument, or part of entering the function?
The answers determine what gets destroyed when an exception is thrown
in the process of evaluating an argument expression. It also
determines the order of destruction, since parameters aren't
temporary variables, they have to be destroyed immediately on return
rather than at the end of the full-expression. If they are created
as part of the argument evaluation the order of destruction could be
different from the order of creation. Suppose there is an exception
thrown in the copy constructor. Do all parameters have to have been
evaluated?
If we interpret this strictly I don't see how we can ever eliminate
copy constructors for parameters, since the rules for destruction of
local temps and parameters are different.
My preferred solutions, in order of preference.
1. Initialization is part of argument evaluation and even parameters
can be treated as temps and left to the end of the full expression.
2. Initialization is separate and occurs after argument evaluation.
Conversion is considered part of argument evaluation.
If a copy constructor is eliminated the "parameter" is what is
eliminated and the temp isn't destroyed until the end of the
full expression.
3. like 2, but conversion is part of the initialization
4. A strict interpretation requiring that parameters be initialized
only after arguments are evaluated. This seems to me to
eliminate the optimization of copy constructors.
Resolution:
Requestor: Mike Ball
Owner: Josee Lajoie (order of construction/destruction)
Emails:
core-5854
Papers:
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Work Group: Core
Issue Number: 452a
Title: How does name look up work after . or -> for namespace names
or template names?
Section: 5.2.4 [expr.ref] Class member access
Status: active
Description:
5.2.4 says p3:
"If the nested-name-specifier of the qualified-id specifies a
namespace name, the name is looked in the context in which the
entire postfix-expression occurs."
This is backward. One doesn't know if the name is a namespace name
until the name has been looked up. In which scope must the name
following the . or -> operator be first looked up?
namespace N { }
struct S {
class N { };
};
S s;
... s.N::b ...
The scope of the object-expression 's' or the scope in which the
entire expression takes place?
--------
Neal Gafter also asks:
"In the syntax
p->template T<args>::x
in which scope(s) is T looked up?"
template <class X> class T { static X x; };
class C {
template <class X> class T { static X x; };
};
C* p;
p->template T<args>::x
Resolution:
Requestor:
Owner: Steve Adamczyk (Name Look Up)
Emails:
Papers:
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Work Group: Core
Issue Number: 468
Title: How does dynamic_cast to void* work for non-polymorphic
types?
Section: 5.2.6 [expr.dynamic.cast]
Status: active
Description:
5.2.6 p7 says:
"If T is 'pointer to cv void', then the result is a pointer to the
complete object pointed (referred) to by v. Otherwise the run-time
check is applied ..."
Does this apply to pointers to non-polymorphic types?
class A { };
class B { };
class C : public A, public B { };
C c;
B* pb = &c;
dynamic_cast<void*>(pb); // will this return a pointer to the
// object c?
Resolution:
Requestor:
Owner: Bill Gibbons (RTTI)
Emails:
Papers:
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Work Group: Core
Issue Number: 483
Title: What does a compiler know about type_info if the header
isn't included?
Section: 5.2.7 [expr.typeid] Type identification
Status: active
Description:
If you don't include <typeinfo> and you do a typeid(...), do you get
an error ("<typeinfo> must be included before using typeid")?
Or is the type type_info built-in in some way?
If so, why do we define it in a header?
Or perhaps the compiler predeclares type_info, but you have to
include the header to get the definition, which means you could do a
typeid(...) but then you couldn't do much with the result because
type_info is incompletely-defined.
Resolution:
Requestor: Steve Adamczyk
Owner: Bill Gibbons (RTTI)
Emails:
core-5463
Papers:
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Work Group: Core
Issue Number: 486
Title: Can a value of enumeration type be converted to pointer type?
Section: 5.2.9 [expr.reinterpret.cast]
Status: active
Description:
5.2.9 p5 says:
"A value of integral type can be explicitly converted to pointer
type."
Can a value of enumeration type be explicitly converted to pointer
type?
Proposal:
Add to the sentence above: "... of integral type or enumeration
type..."
Resolution:
Requestor: Bill Gibbons
Owner: Steve Adamczyk (Type Conversions)
Emails:
Papers:
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Work Group: Core
Issue Number: 487
Title: Conversions to pointer to member functions need to be
changed to allow covariant return types
Section: 5.2.9 [expr.reinterpret.cast]
Status: active
Description:
5.2.9 p11 says:
"Calling a member function through a pointer to member that
represents a function type that differs from the function type
specified on the member function declaration results in undefined
behavior."
This needs to be clarified wrt pointer to member functions that
differ because they represent virtual functions that differ only
because of their covariant return type.
Proposal:
Add at the end of paragraph 2:
"... (except that an overriding virtual function with a different
return type may be called (10.4))."
Erwin Unruh also notes:
There are implicit conversions, which alter the type of a 'pointer
to member function' according to the class of which it is a member.
How does it interact with this sentence?
Resolution:
Requestor: Bill Gibbons
Owner: Steve Adamczyk (Type Conversions)
Emails:
Papers:
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Work Group: Core
Issue Number: 538
Title: Are user-defined conversions invoked as the result of a
reinterpret_cast?
Section: 5.2.9 [expr.reinterpret.cast]
Status: active
Description:
struct A {
operator void* ();
} a;
main() {
int i = reinterpret_cast<int>(a);
}
Is A::operator void* invoked as the result of the reinterpret_cast?
Resolution:
Requestor: Jason Merrill
Owner: Steve Adamczyk (Type conversions)
Emails:
core-5913, core-5939 and followings.
Papers:
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Work Group: Core
Issue Number: 528
Title: can sizeof be applied to a reference type?
Section: 5.3.3 [expr.sizeof]
Status: active
Description:
What is the state of the following statement?
int a = sizeof(int&);
Erwin proposed that the statement to be ill-formed.
What about the following?
template<class T> size_t size(T) { return sizeof(T); }
size<int&>(i); // allowed?
Resolution:
Requestor: Erwin Unruh
Owner: Steve Adamczyk (Types)
Emails:
core-5686
Papers:
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Work Group: Core
Issue Number: 435
Title: Can reference types be newed?
Section: 5.3.4 [expr.new] New
Status: closed
Description:
p2 says:
"The new-type in a new-expression is the longest possible
sequence of new-declarators. This prevents ambiguities
between declarator operators &, *, [], and their expression
counterparts."
This indicates that:
'new int & i'
will be parsed as: (new int&)i
what does it mean to new a reference type?
Proposal:
No, reference types cannot be newed.
(The syntax does not allow for it).
The second sentence of 5.3.4 p2 should be changed as follows:
"This prevents ambiguities between declarator operators *, [], and
their expression counterparts."
Resolution:
See Monterey motion 9.
Also see paper X3J16/95-0148, WG21/N0748
Requestor:
Owner: Josee Lajoie (New)
Emails:
Papers:
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Work Group: Core
Issue Number: 436
Title: What is the type of a new expression allocating an array?
Section: 5.3.4 [expr.new] New
Status: closed
Description:
5.3.4p6 says:
"When the allocated object is an array ... the new-expression yields
a pointer to the initial element of the array."
Bill Gibbons says:
The type of the expression 'new T' should be T* (always). The
decay to pointer to first element should only occur when the
explicit array bound is used in the new expression. This allows
template argument to be used to allocate arrays.
Resolution:
The WP is already clear.
Requestor: Bill Gibbons
Owner: Josee Lajoie (New)
Emails:
core-3709
Papers:
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Work Group: Core
Issue Number: 453
Title: Can operator new be called to allocate storage for
temporaries, RTTI or exception handling?
Section: 5.3.4 [expr.new] New
Status: active
Description:
Is it permitted for an implementation to create temporaries on the
heap rather than on the stack? If so, does that require that
operator new() be accessible in the context in which such a
temporary is created? Is an implementation allowed to call a
replaced operator new whenever it likes (storage for RTTI, exception
handling, initializing static in a library)?
Core 1 discussed this issue in Monterey.
This is the resolution the WG seemed to converge towards:
The storage for variables with static storage duration, for data
structures used for RTTI and exception handling cannot be acquired
with operator new.
global operator new/delete (either the user-defined ones or the
implementation-supplied ones) will only be called from new/delete
expressions and by the functions in the library.
I will write a paper for the Tokyo meeting.
Resolution:
Requestor: Mike Miller
Owner: Josee Lajoie (New)
Emails:
core-5068
Papers:
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Work Group: Core
Issue Number: 469
Title: Better name lookup rules for operator new needed
Section: 5.3.4 [expr.new] New
Status: closed
Description:
5.3.4 is not clear regarding how the operator new is selected (name
lookup) in the following situations:
o the syntax ::new and ::delete have special meaning.
new and delete are keywords and not function names when used as
follows
int* pi = ::new int;
::delete pi;
we need to be explicit in 5.3.4 and 5.3.5 to say that the syntax
::new calls global operator delete and ::delete calls global
operator delete.
o if a new with placement operator can be defined in a namespace
scope (other than global scope), we need to describe how a new
operator is looked up for a new expression that uses placement
syntax.
Resolution:
See Monterey motion 9.
Also see paper 95-0148/N0748.
Requestor: Steve Clamage
Owner: Steve Adamczyk (Name Lookup)
Emails:
Papers:
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Work Group: Core Language
Issue Number: 340
Title: Which delete operator must be used to delete objects and
arrays?
Section: 5.3.5 [expr.delete] Delete
Status: active
Description:
Section 5.3.5 says:
"In the ... alternative (delete object), the value of the
operand of delete shall be a pointer to a non-array object
created by a new expression."
This statement fail to take account of the fact that an "array
object" may itself be considered to be an "individual object".
Here is an example which illustrates this point:
typedef int array_type[20];
void foobar ()
{
array_type *p = (array_type *) new array_type;
delete p; // undefined behavior???
}
In this example, the current rules fail to make it completely clear
whether or not the delete statement shown produces undefined
behavior. Only one "object" is being deleted here, but that object
happens to have an array type (a fact which the implementation could
easily deduce from the static type of the pointer expression `p'
given in the delete statement).
Bill Gibbons also notes:
This is also a problem when delete is used in template definitions.
template <class T> void f(T* pt) {
delete pt; // What form of delete should be used here?
}
If T happens to be an array type, than the form of delete selected
here is not appropriate.
Bill Gibbons indicated the WP should be made clearer to better
describe the committee resolution adopted earlier:
It should be made clear that the *syntax* of the delete expression
must match the type of the object allocated by new *not* the syntax
of the new expression.
Resolution:
Requestor: Ron Guilmette
Owner: Josee Lajoie (Delete)
Emails:
core-3709
Papers:
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Work Group: Core Language
Issue Number: 416
Title: Can a delete expression be of abstract type?
Section: 5.3.5 [expr.delete] Delete
Status: active
Description:
Ron would like to see the following rules apply to the
cast-expression of a delete expression:
The referent type of the cast-expression may be an
abstract class type, provided that this type was earlier
defined to contain a virtual destructor.
Resolution:
Requestor: Ron Guilmette
Owner: Josee Lajoie (Object Model)
Emails:
Papers:
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Work Group: Core
Issue Number: 426
Title: Deleting arrays if dynamic type differs from type of delete
expression
Section: 5.3.5 [expr.delete] Delete
Status: editorial
Description:
5.3.5p3
"In the first alternative (delete object), if the static type of the
operand is different from its dynamic type, the static type shall
have a virtual destructor or the behavior is undefined. In the
second alternative (delete array), if the dynamic type of the
object to be deleted differs from its static type, the behavior is
undefined."
1) this needs to be more specific and say that there must exist an
inheritance relationship between the static type and the dynamic
type, i.e.
"if the static type of the operand is different from its dynamic
type, the static type shall be a base class of the operand's
dynamic type and the static type must have a virtual
destructor..."
2) Jerry Schwarz asks for the following:
Current WP disallows deleting an array using a pointer with a
static type different from the type used in allocation.
That is it prohibits
class B {
virtual ~B() ;
} ;
class D : public B { } ;
B* pb = new D[10] ;
delete[] pb ;
This used to make some sense because the overheads of figuring
out exactly what to do might be significant. (E.g. in the
presence of MI pb might not even point to the start of the
array.)
But now that we have RTTI, there has to be enough information
(in the vtbl) to determine the beginning of the array and its
type.
So I believe that this prohibition could reasonably be lifted.
Resolution:
1) Core 1 decided at the Monterey meeting that this is an editorial
issue.
2) Proposal for an extension. (will not be considered).
Requestor:
Owner: Josee Lajoie (delete)
Emails:
Papers:
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Work Group: Core
Issue Number: 470
Title: deleting a pointer allocated by a new with placement
Section: 5.3.5 [expr.delete] Delete
Status: active
Description:
5.3.5 p2 says:
"... in the first alternative (delete object), the value of the
operand of delete shall be a pointer to a non-array object created
by a new-expression without a new-placement specification, ..."
In some situations, it is well-defined what happens even when new
with placement was called. Do we want to prohibit these cases?
Erwin Unruh also notes:
The deletion of a pointer gained by a placement new must be allowed.
Using the default operator delete for a pointer gained by the
library
placement new is undefined. However, a user may write placement news
that allocate storage in which case using delete on a pointer
returned by such a placement new should be well-defined.
Resolution:
Mike Miller will provide a paper for for the Tokyo meeting (November
1995).
Requestor: Jason Merrill
Owner: Mike Miller (new / delete)
Emails:
core-5569
Papers:
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Work Group: Core
Issue Number: 471
Title: When can an implementation change the value of a delete
expression?
Section: 5.3.5 [expr.delete] Delete
Status: active
Description:
5.3.5p4
"If the expression denoting the object in a delete-expression is a
modifiable lvalue, any attempt to access its value after the
deletion is undefined."
When can an implementation change the pointer value of a delete
expression?
inline void* operator new(void* p) { return p; }
struct Base { virtual ~Base() {} };
struct Immortal : Base {
operator delete(void* p) { new(p) Immortal; }
};
main()
{
Base* bp = new Immortal;
delete bp;
delete bp;
delete bp;
}
Is the above well-formed?
Resolution:
Requestor: Nathan Myers
Owner: Josee Lajoie (Memory Model)
Emails:
core-5565
Papers:
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Work Group: Core Language
Issue Number: 93
Title: Deleting the "current object" (this) in a member function
Section: 5.3.5 [expr.delete] Delete
Status: active
Description:
In a standard conforming program, may delete be used within a
non-static member function (or within a function which is called
directly or indirectly by such a function) to delete the object for
which the non-static member function was called?
Example:
struct S { void member (); };
void delete_S (S *arg) { delete arg; }
void S::member ()
{
delete_S (this);
}
If this is prohibited in a standard conforming program is a standard
conforming implementation required to issue a diagnostic for such
code?
Proposal:
The WP should say somewhere that accessing memory after is has been
deallocated results in undefined behavior.
Resolution:
Requestor: Ron Guilmette
Owner: Josee Lajoie (Memory Model)
Emails:
core-1650
Papers:
94-0185/N0572
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Work Group: Core
Issue Number: 488
Title: Can a pointer to a mutable member be used to modify a const
class object?
Section: 5.5 [expr.mptr.oper]
Status: active
Description:
5.5 p4 says:
"The restrictions on cv-qualification, and the manner in which
cv-qualifiers of the operands are combined to produce the
cv-qualifiers of the result, are the same as the rules for E1.E2..."
It should be noted that a pointer to member that refers to a mutable
member cannot be used to modify a const class object.
struct S {
mutable int i;
};
const S cs;
int S::* pm = &S::i;
cs.*pm = 88;
Proposal:
Add a note at the end of p4:
"Note: a pointer to member that refers to a mutable member cannot be
used to modify a member of an object of const class type."
Resolution:
Requestor: Bill Gibbons
Owner: Bill Gibbons (pointer to member)
Emails:
Papers:
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Work Group: Core
Issue Number: 489
Title: Can the operands of the multiplicative operators be of
enumeration type?
Section: 5.6 [expr.mul] Multiplicative operators
Status: closed
Description:
5.6 p2 says:
"The operands of * and / shall have arithmetic type; the operands of
% shall have integral type."
Can the operand of the multiplicative operators be of enumeration
type?
Proposal:
Change the sentence above as follows:
"The operands of * and / shall have arithmetic or enumeration type;
the operands of % shall have integral or enumeration type."
Resolution:
See Monterey motion 2i.
Requestor: Bill Gibbons
Owner: Steve Adamczyk (Types)
Emails:
Papers:
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Work Group: Core
Issue Number: 490
Title: Can the operands of the additive operators be of enumeration
type?
Section: 5.7 [expr.add] Additive Operators
Status: closed
Description:
5.7 omits to include in its description enumeration type.
Proposal:
Change the text in 5.7 as follows:
"1 ...
For addition, either or both operands shall have arithmetic _or
enumeration type_, or one shall be a pointer to a completely
defined object type and the other shall have integral _or
enumeration type_.
2 For substraction, one of the following shall hold:
-- both operands have arithmetic _or enumeration type_;
-- both operands are pointers to cv-qualified or cv-unqualified
versions of the same completely defined object type; or
-- the left operand is a pointer to a completely defined object
type and the right operand has integral _or enumeration type_.
3 If both operand have arithmetic _or enumeration type_, the usual
arithmetic conversions are performed on them. ...
...
5 When an expression that has integral _or enumeration type_ is
added to, or substracted from a pointer, ...
...
Footnote 47:
In this scheme the integral _or enumeration expression_ added or
substracted from the converted pointer..."
Resolution:
See Monterey motion 2i.
Requestor: Bill Gibbons
Owner: Steve Adamczyk (Types)
Emails:
Papers:
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Work Group: Core
Issue Number: 491
Title: Can the operands of the shift operators be of enumeration
type?
Section: 5.8 [expr.shift] Shift Operators
Status: closed
Description:
5.8 p1 says:
"The operands shall be of integral type and integral promotions are
performed."
Can the operand of the shift operators be of enumeration type?
Proposal:
Change the sentence above as follows:
"The operands shall be of integral or enumeration type and integral
promotions are performed."
Resolution:
See Monterey motion 2i.
Requestor: Bill Gibbons
Owner: Steve Adamczyk (Types)
Emails:
Papers:
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Work Group: Core
Issue Number: 492
Title: Can the operands of the relational operators be of
enumeration type?
Section: 5.9 [expr.rel] Relational Operators
Status: closed
Description:
5.9 says:
"1 ...
The operands shall have arithmetic or pointer type. ...
2 The usual arithmetic conversions are performed on arithmetic
operands. ..."
Can the operands of the relational operators be of enumeration type?
Proposal:
Change the sentences above as follows:
"1 ...
The operands shall have arithmetic, enumeration or pointer
type. ...
2 The usual arithmetic conversions are performed on operands of
arithmetic or enumeration type. ..."
Resolution:
See Monterey motion 2i.
Requestor: Bill Gibbons
Owner: Steve Adamczyk (Types)
Emails:
Papers:
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Work Group: Core
Issue Number: 493
Title: Better description of the cv-qualification of the result of
a relational operator needed
Section: 5.9 [expr.rel] Relational Operators
Status: active
Description:
5.9p2 says:
"Pointer conversions are performed on the pointer operands to bring
them to the same type, which shall be a cv-qualified or
cv-unqualified version of the type of one of the operands."
This seems to imply that the result has exactly the type of one of
the operands, or an unqualified version of that type. In fact, the
common type may have more qualifiers than either operand type.
Proposal:
Change the text above to say:
"... which shall be the type of one of the operands, cv-qualified
with the combined cv-qualifiers of the operands' types."
Resolution:
Requestor: Bill Gibbons
Owner: Steve Adamczyk (Type Conversions)
Emails:
Papers:
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Work Group: Core
Issue Number: 513
Title: Are pointer conversions implementation-defined or
unspecified?
Section: 5.9 [expr.rel] Relational Operators
Status: active
Description:
5.9p2 last '--' says:
"Other pointer comparisons are implementation-defined."
Comparison of unrelated pointers should be unspecified or undefined.
At present it reads implementation defined, but I doubt that the
exact rules can be described by a compiler vendor.
Proposal:
Change the text above to say:
"Other pointer comparisons are unspecified."
Resolution:
Requestor: Erwin Unruh
Owner: Steve Adamczyk (Type Conversions)
Emails:
Papers:
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Work Group: Core
Issue Number: 481
Title: What are the semantics for pointer to member comparison?
Section: 5.10 [expr.eq] Equality operators
Status: closed
Description:
struct B {
int x;
int f() { return x; }
B(int a) :x(a) {}
};
struct L : B{ L(int a) : B(a) {} };
struct R : B{ R(int a) : B(a) {} };
struct D : L,R{ D() : L(1), R(2) {} };
int (B::*pb)() = &B::f;
int (L::*pl)() = pb;
int (R::*pr)() = pb;
int (D::*pdl)() = pl;
int (D::*pdr)() = pr;
assert(pdl != pdr); // Is this true?
D d;
cout << (d.*pdl)();
cout << (d.*pdr)();
What does it mean to compare two member pointers for equality?
Do they compare equal if they are the same member?
Or do they compare equal if the have the same behavior?
Resolution:
See Monterey motion 2l.
Requestor: John Max Skaller
Owner: Josee Lajoie (Pointer to Members)
Emails:
core-5391
Papers:
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Work Group: Core
Issue Number: 494
Title: Can the operands of the bitwise operators be of enumeration
type?
Section: 5.11 [expr.bit.and], 5.12 [expr.xor], 5.13 [expr.or]
Status: closed
Description:
All these subclauses say:
"The operator applies only to integral operands."
Can the operands of the bitwise operators be of enumeration type?
Proposal:
Change the sentence above to say:
"The operator applies only to operands of integral or enumeration
types."
Resolution:
See Monterey motion 2i.
Requestor: Bill Gibbons
Owner: Steve Adamczyk (Types)
Emails:
Papers:
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Work Group: Core
Issue Number: 495
Title: Can the operands of the conditional operator be of
enumeration type?
Section: 5.16 [expr.cond] Conditional operator
Status: closed
Description:
5.16 p3 says:
"If both the second and the third expressions are of arithmetic type,
then if they are of the same type the result is of that type; ..."
Can the operands of the conditional operator be of enumeration type?
Proposal:
Change the sentence above to say:
"If both the second and the third expressions are of arithmetic or
enumeration type, ..."
Resolution:
See Monterey motion 2i.
Requestor: Bill Gibbons
Owner: Steve Adamczyk (Types)
Emails:
Papers:
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Work Group: Core
Issue Number: 472
Title: lvalue-> rvalue transformation for the operands of the
conditional operator needs better description
Section: 5.16 [expr.cond] Conditional operator
Status: active
Description:
It is not clear when the lvalue-> rvalue transformation takes place
on the operands of the conditional operator.
5.16 p3 says:
"If both the second and the third expressions are of arithmetic
type, then if they are of the same type, the result is that type,
otherwise the usual arithmetic conversions are performed to bring
them to a common type."
Does "type" in this sentence include cv-qualifiers?
Other sentences in this paragraph seem to indicate that the
cv-qualifiers remain a part of the operands type:
"if both the second and the third expressions have type 'cv void',
the common type is 'cv void'".
Resolution:
Requestor:
Owner: Steve Adamczyk (Type conversions)
Emails:
Papers:
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Work Group: Core
Issue Number: 496
Title: The cv-qualification of the result of the conditional
operator needs better description
Section: 5.16 [expr.cond] Conditional operator
Status: active
Description:
5.16p3 says:
"...pointer conversions are performed on the pointer operands to
bring them to a common type, which shall be a cv-qualified or
cv-unqualified version of the type of either the second or the
third expression.
...
if both the second and the third expressions are lvalues of related
class types, they are converted to a common type (which shall be
a cv-qualified or cv-unqualified version of the type of either the
second or the third expression)..."
This seems to imply that the result has either exactly the type of
the second or third expression, or the unqualified version of that
type. In fact, the common type may have more qualifiers than either
operand type.
Proposal:
Change the text above to say:
"... which shall be the type of either the second or the third
expression, cv-qualified with the combined cv-qualifiers of the
types of the second and third expression."
Resolution:
Requestor: Bill Gibbons
Owner: Steve Adamczyk (Type Conversions)
Emails:
Papers:
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Work Group: Core
Issue Number: 497
Title: The conversion applied to operands of the conditional
operator of class type needs to be better described
Section: 5.16 [expr.cond] Conditional operator
Status: active
Description:
5.16p3 says:
"... if the second and the third expressions are lvalues of related
class types..."
The term "related class type" is not defined.
The sentence above should be changed to say:
"... are lvalues of class type, and one class is an unambiguous
public base of the other, ..."
Resolution:
Requestor: Bill Gibbons
Owner: Steve Adamczyk (Type Conversions)
Emails:
Papers:
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Work Group: Core
Issue Number: 498
Title: Can the operands of the assignment operator be of enumeration
type?
Section: 5.17 [expr.ass] Assignment operators
Status: closed
Description:
5.17 p7 says:
"In += and -=, E1 shall either have arithmetic type or be a pointer
to a possibly cv-qualified completely defined object type."
Can the operands of the assignment operator be of enumeration type?
Change the sentence above as follows:
"In += and -=, E1 shall either have arithmetic or enumeration type
or be a pointer to a possibly cv-qualified completely defined
object type."
Resolution:
See Monterey motion 2i.
Requestor: Bill Gibbons
Owner: Steve Adamczyk (Types)
Emails:
Papers:
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Work Group: Core
Issue Number: 499
Title: When are temporaries destroyed when created by the left
expression of the comma operator?
Section: 5.18 [expr.comma] Comma operator
Status: editorial
Description:
5.18 p1 says:
"All side effects of the left expression are performed before the
evaluation of the right expression."
When are temporaries destroyed when created by the left expression
of the comma operator?
Change the sentence above as follows:
"All side effects of the left expression, except for destruction of
temporaries (12.2), are performed before the evaluation of the
right expression."
Resolution:
Core 1 decided at the Monterey meeting that this is an editorial
issue.
Requestor: Bill Gibbons
Owner: Josee Lajoie (Temporaries)
Emails:
Papers:
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Work Group: Core
Issue Number: 537
Title: Can the implementation accept other constant expressions?
Section: 5.19 [expr.const] Constant expressions
Status: active
Description:
The C standard says, in its section on constant expressions:
"An implementation may accept other forms of constant expressions."
Should C++ say the same thing?
In particular, implementations often accept extended forms of
constant expressions in order to support 'offsetof', defined as
returning an 'integral constant expression'. Are implementations
prohibited to accept other forms of 'integral constant expressions',
expressions which the WP does not describe as constant expressions?
If, in C++, implementations are not allowed to extend the set of
constant expressions, then the C compatibility appendix should list
this as an incompatibility.
Resolution:
Requestor: Dave Hendricksen
Owner: Tom Plum (C compatibility)
Emails:
Papers:
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
=============================================================================
Chapter 6 - Statements
------------------------
Work Group: Core
Issue Number: 500
Title: Can one jump over the definition of a variable of
enumeration type?
Section: 6.7 [stmt.dcl] Declaration statement
Status: editorial
Description:
6.7p3 says:
"A program that jumps from a point where a local variable with
automatic storage duration is not in scope to a point where it is in
scope is ill-formed unless the variable has pointer or arithmetic
type or is an aggregate, and is declared without an initializer."
Can one jump over a declaration for a variable of enumeration type?
Also, since an aggregate can have members with non-trivial
constructors, using aggregate here is not appropriate.
Proposal:
Change the sentence above to say:
"... from a point where a local variable with automatic storage
duration is not in scope to a point where it is in scope is
ill-formed unless the variable has POD type and is declared without
an initializer."
Resolution:
Folks doing editorial work in Monterey decided to treat this issue as
an editorial issue.
Requestor: Bill Gibbons
Owner: Josee Lajoie (Initialization / Destruction)
Emails:
Papers:
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Work Group: Core
Issue Number: 524
Title: Exactly when are objects of automatic storage duration
destroyed?
Section: 6.7 [stmt.dcl] Declaration statement
Status: active
Description:
6.7p5 says:
"The destructor is called either immediately before or as part of the
calls of the atexit functions."
What if the atexit function is not called?
Resolution:
Requestor: Sean Corfield
Owner: Josee Lajoie (Destruction)
Emails:
Papers:
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Work Group: Core
Issue Number: 132 (WMM.83)
Title: Consistency between "::" and "Class::" in declarations
Section: 6.8 [stmt.ambig] Ambiguity resolution
Status: active
Description:
WMM.83. Is a change necessary for syntactic consistency between the
treatment of "::" and "class::" in declarations?
float a;
float b;
main(){
int (a) ; // valid block scope redeclaration of a
int (::b); // valid function like cast of b
}
Note that the reason for the "function like cast" interpretation is
that "::b" can *only* be used as a reference, and never used as a
declarator.
struct T { static a;};
int (T::a); // valid declaration and definition of T::a
main(){
int (T::a); // semantic error: attempt to redeclare T::a
(int)(T::a); // cast of T::a
}
Since the syntax allows "T::a" to be used as a declarator, the
statement: int (T::a); is interpreted as a declaration even though
this declaration is not valid at block scope.
And eventhough the statement: int (T::a); is an invalid block scope
declaration, it is not interpreted as an expression because it is
validated as a declaration by the grammar.
Should the syntax "Class::" always be interpreted as a reference
instead of a part of a declaration when placed inside block scope?
Resolution:
Requestor: Mike Miller / Jim Roskin
Owner: Anthony Scian (Syntax)
Emails:
core-629
Papers:
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Work Group: Core
Issue Number: 424
Title: Must disambiguation update symbol tables?
Section: 6.8 [stmt.ambig] Ambiguity resolution
Status: active
Description:
The question is about the following sentence from 6.8p3 [stmt.ambig]
WP> The disambiguation is purely syntactic; that is, the meaning of
WP> the names, beyond whether they are type-ids or not, is not used
WP> in the disambiguation.
On the one hand, this would imply that a trial parser needn't update
a symbol table, since that would be processing that is not purely
syntactic.
On the other hand, some input would be disambiguated differently if
the symbol table were updated during trial parsing. Symbol table
updates would determine which names will be type-ids during the
actual parse.
To be more concrete and specific about the problem, consider the
statement in main() in the enclosed test case. Should this be
disambiguated as a declaration with a syntax error, or should it be
disambiguated as a well-formed expression?
struct T1
{
T1 operator()(int x) { return T1(x); };
int operator=(int x) { return x; };
T1(int) {};
};
struct T2
{
T2(int) {};
};
int a, (*(*b)(T2))(int), c, d;
void main ()
{
// Is the following a declaration with a syntax error?
// Or is it a semantically valid expression?
T1(a) = 3,
T2(4),
(*(*b)(T2(c)))(int(d));
}
Resolution:
Requestor: Neal M Gafter <gafter@mri.com>
Owner: Anthony Scian (Syntax)
Emails:
Papers:
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
=============================================================================
Chapter 7 - Declarations
--------------------------
Work Group: Core
Issue Number: 213
Title: Should vacuous type declarations be prohibited?
Section: 7 [dcl.dcl] Declarations
Status: active
Description:
7p3: Should the draft prohibit vacuous decls like this?
enum { };
class { int i; };
class { };
typedef enum {};
Resolution:
Requestor: Tom Plum / Dan Saks
Owner: Steve Adamczyk (Types)
Emails:
Papers:
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Work Group: Core
Issue Number: 437
Title: How do extern declarations link with previous declarations?
Section: 7.1.1 [dcl.stc] Storage class specifiers
Status: closed
Description:
3.5 paragraph 6:
"The name of a function declared in a block scope or a variable
declared extern in a block scope has linkage, either internal or
external to match the linkage of prior visible declarations of the
same name in the same translation unit, but if there is no prior
visible declaration it has external linkage."
7.1.1 paragraph 5:
"...An object or function introduced by a declaration with an extern
specifier has external linkage unless the declaration matches a
visible prior declaration at namespace scope of the same object or
function, in which case the object or function has the linkage
specified by the prior declaration."
These two sentences are similar but not identical. It would be
better to eliminate gratuitous differences, or consolidate them in
one place if possible. This is true of the whole discussion of
linkage in these two sections.
Consider the following translation unit:
static x; /* internal linkage */
void f() {
auto x; /* no linkage */
{
extern x; /* linkage unclear by 3.5, since the prior visible
declaration has no linkage.
external linkage by 7.1.1, since there is no
visible name with namespace scope. */
}
}
Proposal:
Change the sentence in 3.5 as follows:
"The name of a function declared in a block scope or a variable
declared extern in a block scope has external linkage, unless the
declaration matches a visible declaration of namespace scope with
internal linkage, in which case the object or function has internal
linkage."
Resolution:
See Monterey motion 8.
Also see 95-0147/N0747.
Requestor: Mike Holly
Owner: Josee Lajoie (Linkage)
Emails:
core-5056
Papers:
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Work Group: Core
Issue Number: 473
Title: linkage of local static variables needs to be better
described
Section: 7.1.1 [dcl.stc] Storage class specifiers
Status: closed
Description:
3.5 paragraph 7 says:
"Names not covered by these rules have no linkage. Moreover, except
as noted a name declared in a local scope (3.3.1) has no linkage."
7.1.1 paragraph 4 says:
"A name declared with a static specifier in a scope other than class
scope (3.3.5) has internal linkage."
The latter would seem to imply that both functions in the following
translation unit are modifying the same object:
void f() {static int x; x++;}
void g() {static int x; x++;}
Proposal:
Change 7.1.1 para 4 to say:
"A name declared with a static specifier in a namespace scope has
internal linkage, and in a block scope has no linkage."
Resolution:
See Monterey motion 8.
Also see 95-0147/N0747.
Requestor: Mike Holly
Owner: Josee Lajoie (Linkage)
Emails:
Papers:
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Work Group: Core
Issue Number: 454
Title: Can two inline functions call one another?
Section: 7.1.2 [dcl.fct.spec] Function specifiers
Status: closed
Description:
p3 says:
"A call to an inline function shall not precede its definition."
Doesn't this prohibit existing practice?
class X {
void f() { g(); }
void g() { h(); }
};
Proposal:
Replace the sentence above in 7.1.2 p3 with:
"An inline function must be declared inline before it is used."
Resolution:
See Monterey motion 8.
Also see 95-0147/N0747.
Requestor: John Max Skaller
Owner: Josee Lajoie (Linkage)
Emails:
core-5061
Papers:
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Work Group: Core
Issue Number: 502
Title: What is the linkage name of unnamed enum types introduced
by a typedef?
Section: 7.1.3 [dcl.typedef] The typedef specifier
Status: closed
Description:
The rules described in 7.1.3 p5 apply to enumeration types as well.
Proposal:
Change the text in 7.1.3 p5 as follows:
"An unnamed class _or enum_ defined in a declaration with a typedef
specifier gets a dummy name. For linkage purposes only, the first
typedef-name declared by the declaration is used to denote the
class type _or enumeration type_ in the place of the dummy name.
...
The typedef-name is still only a synonym for the dummy name and
shall not be used where a true class name _or enum name_ is
required.
...
If an unnamed class _or enum_ is defined in a typedef declaration
but the declaration does not declare a class type _or enumeration
type_, the name of the class for linkage purposes is a dummy name."
And delete paragraph 6, which becomes unnecessary.
Resolution:
See Monterey motion 8.
Also see 95-0147/N0747.
Requestor: Bill Gibbons
Owner: Josee Lajoie (Linkage)
Emails:
Papers:
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Work Group: Core
Issue Number: 116 (WMM.65)
Title: Is "const class X { };" legal?
Section: 7.1.5 [dcl.type] Type Specifiers
Status: active
Description:
Is "const class X { };" legal, and, if so, what does it mean?
Resolution:
Requestor: Mike Miller
Owner: Steve Adamczyk (Classes)
Emails:
Papers:
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Work Group: Core
Issue Number: 503
Title: Better semantics of bitfields of enumeration type needed
Section: 7.2 [dcl.enum] Enumeration declarations
Status: active
Description:
7.2p5 describes the underlying type of enumeration types.
It should be made clear that this description does not apply to
the underlying type of enumeration bit-fields.
Also, something should be said about the signedness of enumeration
types. Bill Gibbons's suggested words:
"Even though the underlying type of an enumeration type will be
either signed or unsigned, enumerations themselves are neither
signed nor unsigned. [For example, a two-bit bit-field can hold an
enumeration with values {0,1,2,3}.]"
Resolution:
Requestor: Bill Gibbons
Owner: Steve Adamczyk (Types)
Emails:
Papers:
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Work Group: Core
Issue Number: 474
Title: Lookup of namespace names in alias declarations
Section: 7.3.2 [namespace.alias]
Status: active
Description:
Are names used in namespace-alias-definitions looked up only as
namespace names?
namespace very_long_name { }
void f() {
int very_long_name;
namespace VLN = very_long_name; //1
}
Does the namespace-alias-definition on line //1 find the namespace
name very_long_name declared in global scope?
Or is the declaration in error?
Proposal:
When looking up the names mentioned in the
qualified-namespace-specifier of a namespace-alias-definition, only
namespace names are looked up.
Resolution:
Requestor:
Owner: Steve Adamczyk (Name lookup)
Emails:
Papers:
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Work Group: Core
Issue Number: 475
Title: Lookup of namespace names in using directives
Section: 7.3.4 [namespace.udir]
Status: active
Description:
Are names used in using directives looked up only as namespace names?
namespace NS { }
void f() {
int NS;
{
using namespace NS; //1
}
}
Does the using directive on line //1 find the namespace name NS in
global scope?
Proposal:
When looking up the names mentioned in using directives, only
namespace names are looked up.
Resolution:
Requestor:
Owner: Steve Adamczyk (Name lookup)
Emails:
Papers:
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Work Group: Core
Issue Number: 78 (also WMM.38)
Title: Linkage specification and calling protocol
Section: 7.5 [dcl.link] Linkage Specifications
Status: active
Description:
extern "C" {
// Typedef defined in extern "C" blocks:
// What is the linkage of the function pointed at by 'fp'?
typedef int (*fp)(int);
// Type of a function parameter:
// What is the linkage of the function pointed at by 'fp2'?
int f(int (*fp2) (int));
// Can function with C linkage be defined in extern "C"
// blocks?
int f2(int i) { return i; }
// Can static function with C linkage be defined in
// extern "C" blocks?
static int f3(int i) { return i; }
}
If function declarations/definitions placed inside the extern "C"
block have different properties from the ones placed outside these
blocks, many areas of the C++ language will have to be aware of
difference.
i.e.
a. function overloading resolution
b. casting
one will need to be able to cast from a pointer to a function
with linkage "X" to a pointer to a function with linkage "Y".
In short, it needs to be determined to what extent the linkage is
part of the type system.
[ JL: ]
The standard should not force implementations to accept the
following code:
extern "SomeLinkage" int (*ptr)();
int (*ptr_CXX)();
ptr_CXX = ptr; // 1
i.e. an implementation should be able to issue an error for
line (// 1).
See 95-0122/N0722 for a proposed resolution.
Core 1 discussed this issue in Monterey. The consensus the group
seemed to converge towards was to leave it implementation defined
whether or not the linkage specification is part of the type.
I will present a paper for the Tokyo meeting to propose a possible
resolution.
Resolution:
Requestor: John Armstrong (johna@kurz-ai.com)
Owner: Josee Lajoie (Linkage)
Emails:
core-1583, core-1584, core-1585, core-1586, core-1587, core-1589
core-1590, core-1591, core-1594, core-1595, core-1597, core-1598
core-1599, core-1608, core-1609, core-1612
core-920 (Hansen),core-985 (O'Riordan),core-1064 (Miller)
Papers: 94-0034/N0421
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Work Group: Core Language
Issue Number: 420
Title: Linkage of C++ entities declared within `extern "C"'.
Section: 7.5 [dcl.link] Linkage Specification
Status: active
Description:
Given a declaration or definition of some C++ entity (e.g. a data
member, a function member, and overloaded operator, an anonymous
union object, etc) whose existance within an otherwise standard
conforming program written in ANSI/ISO C would be a violation of the
language rules, what is the effect of the linkage specification on
the declarations/definitions of the C++ specific entities:
Example:
extern "C" {
struct S {
int data_member;
};
int operator+ (S&, int);
}
Resolution:
Requestor: Ron Guilmette
Owner: Josee Lajoie (Linkage)
Emails:
Papers:
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Work Group: Core Language
Issue Number: 486
Title: What is the effect of multiple linkage declarations?
Section: 7.5 [dcl.link] Linkage Specification
Status: closed
Description:
The grammar allows multiple linkage specifications, like
extern "C" extern "C++" int foo() ;
All 7.5[dcl.link]p2 says is "linkage specifications nest."
Do we really want to allow declarations such as the above?
And if we do, we should say what they mean, i.e.
"When linkage specifications nest the innermost one determines the
linkage".
Resolution:
See Monterey motion 8.
Also see 95-0147R1/N0747R1.
Requestor: Jerry Schwarz
Owner: Josee Lajoie (Linkage)
Emails:
Papers:
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
=============================================================================
Chapter 8 - Declarators
-------------------------
Work Group: Core
Issue Number: 456
Title: What is the linkage of a cv-qualified reference to T?
Section: 8.3.2 [dcl.ref] References
Status: closed
Description:
p1 says:
"At all times during the determination of a type, types of the form
'cv-qualified reference to T' is adjusted to be 'reference to T'."
This only says that cv-qualifiers are ignored during type
determination. Aren't cv-qualifiers ignored for other purposes as
well (establishing the reference's linkage for example)?
For example,
typedef int& IR;
const IR ref = 99;
does 'ref' have internal or external linkage?
Resolution:
See issue 504.
Requestor:
Owner: Steve Adamczyk (Declarators)
Emails:
Papers:
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Work Group: Core
Issue Number: 504
Title: Isn't it ill-formed to directly declare a cv-qualified
reference?
Section: 8.3.2 [dcl.ref] References
Status: editorial
Description:
Isn't the following declaration ill-formed?
int & const cri = ...;
That is, isn't it ill-formed to directly declare a cv-qualified
reference?
Resolution:
Core 2 discussed this issue in Monterey and decided that this
was already clear from the WP text.
However, I believe a note should be added to 8.3.2 paragraph 1 to
emphasize that directly declaring a reference const or volatile is
ill-formed.
Also, it should be made clear that ignoring the cv-qualifiers
in a reference declaration when these are introduced using a typedef
or template argument also means that the linkage of the reference
is not affected by a const cv-qualifier (as Neal Gafter indicated in
his original paper 94-0016).
Requestor: Bill Gibbons
Owner: Steve Adamczyk (Declarators)
Emails:
Papers:
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Work Group: Core
Issue Number: 457
Title: What is the linkage of a cv-qualified array?
Section: 8.3.4 [dcl.array]
Status: active
Description:
p1 says:
"At all times during the determination of a type, types of the form
'cv-qualifier-seq array of N T' is adjusted to be 'array of N
cv-qualifier-seq T'."
This only says that cv-qualifiers are ignored during type
determination. Aren't cv-qualifiers ignored for other purposes as
well (establishing the array's linkage for example)?
For example,
typedef int A[5];
const A x;
What is the linkage of x?
Resolution:
Requestor:
Owner: Steve Adamczyk (Declarators)
Emails:
Papers:
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Work Group: Core
Issue Number: 439
Title: Are there any restrictions on the parameter before the
ellipsis?
Section: 8.3.5 [dcl.fct] Functions
Status: closed
Description:
Can the parameter before the ellipsis be a reference?
Resolution:
See Monterey motion 18.
Requestor:
Owner: Steve Adamczyk (Declarators)
Emails:
Papers:
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Work Group: Core
Issue Number: 482
Title: Are cv-qualifiers allowed in a typedef for a function type?
Section: 8.3.5 [dcl.fct] Functions
status: active
Description:
struct A {
typedef void FTYPE() const;
void f() const;
FTYPE f1;
};
Do f and f1 have the same type?
Bill Gibbons' proposed resolution:
Since const/volatile qualifiers are part of the type of a member
function, they should be allowed on typedefs. Of course if that
ends up putting cv qualification on a non-member, a static member, a
constructor or a destructor, the program is ill-formed - exactly as
if it were done without the typedef.
Bill Gibbons suggested the following change to 8.3.5 [dcl.fct].
Paragraph 3 presently says:
"... A cv-qualifier-spec can only be part of a declaration or
definition of a nonstatic member function, and of a pointer to
member function; see[class.this]. It is part of the function type."
He proposed changing it to:
"... A cv-qualifier-spec can only be part of a declaration or
definition of a nonstatic member function, or part of a
pointer to member function type, or part of a typedef for a
function type; see [class.this]. It is part of the function
type. Typedefs of cv-qualified function types can only be used
to declare nonstatic member functions and to form pointer to member
types."
Resolution:
Requestor: Bill Gibbons
Owner: Steve Adamczyk (Declarators)
Emails:
core-5447
Papers:
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Work Group: Core
Issue Number: 530
Title: Can default arguments appear in out-of-line member function
definitions?
Section: 8.3.6 [dcl.fct.default] Default arguments
status: active
Description:
For example
struct X {
void f(int); // no default argument here
};
void X::f(int = 3) { } // is this allowed?
void g(X* xp) {
xp->f(); // uses default argument from definition
}
This is particularly interesting when the function in question
is a constructor. Adding default arguments outside of the class
definition may add a default constructor to the class.
Resolution:
Requestor: Bill Gibbons
Owner: Steve Adamczyk (Declarators)
Emails:
core-5855 and following messages
Papers:
95-0156=N0756 Default Arguments in Member Function Definition
by John Wilkinson
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Work Group: Core
Issue Number: 531
Title: Is a default argument a context that requires a value?
Section: 8.3.6 [dcl.fct.default] Default arguments
status: active
Description:
extern struct A a_default;
extern struct B b_default;
struct A {
void f(B = b_default);
};
struct B {
void f(A = a_default);
};
A a_default;
B b_default;
inline void A::f(B b) { /* ... */ }
inline void B::f(A a) { /* ... */ }
Is this valid code?
Is the default value only needed if and when the function is called
with less than the full number of arguments?
Resolution:
Requestor: Fergus Henderson
Owner: Steve Adamczyk (Declarators)
Emails:
core-5884
Papers:
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Work Group: Core
Issue Number: 476
Title: Can objects with "indeterminate initial value" be referred
to?
Section: 8.5 [dcl.init] Initializers
status: active
Description:
8.5p6 says:
"If no initializer is specified for an object with automatic or
dynamic storage duration, the object and its subobjects, if any,
have an indeterminate initial value."
The C standard specifies that accessing a variable with
indeterminate value results in undefined behavior, but the C++ draft
contains no such language. Also, a definition of "indeterminate
value" is needed in the C++ standard.
Add the following text at the ned of 8.5 paragraph 6:
"Referring to an object with an indeterminate value results in
undefined behavior."
For the definition of indeterminate value, Steve suggests using C's
definition.
Resolution:
Requestor: Steve Clamage
Owner: Josee Lajoie (Object Model)
Emails:
Papers:
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
=============================================================================
Chapter 9 - Classes
---------------------
Work Group: Core
Issue Number: 514
Title: The list of member types a POD class cannot have is not
complete
Section: 9 [class]
Status: editorial?
Description:
p4 says:
"A POD-struct is an aggregate class that has no members of type
reference, pointer to member, non-POD-struct or non-POD-union.
Similarly, a POD-union is an aggregate union that has no members of
type reference, pointer to member, non-POD-struct or non-POD-union."
This forgets arrays of such types.
Replace the sentences above with:
"A POD-struct is an aggregate class that has no members of type
pointer to member, non-POD-struct, non-POD-union (or array of such
types) or reference. Similarly, a POD-union is an aggregate union
that has no members of type pointer to member, non-POD-struct,
non-POD-union (or array of such types) or reference."
Resolution:
I would like to treat this as an editorial issues. Would there be
any objection?
Requestor:
Owner: Steve Adamczyk (Types)
Emails:
Papers:
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Work Group: Core
Issue Number: 252
Title: Where can the definition of an incomplete class object
appear?
Section: 9.1 [class.name] Class names
Status: active
Description:
must an incomplete class object be completed in the same scope?
9.1p24 In C, a struct-or-union of incomplete type must be
completed in the same scope as the incomplete-type declaration, or it
remains an incomplete type.
[We believe the same is intended for incompletely-defined classes in
C++, but the document is not yet clear enough to tell.]
[ Note JL: ]
The resolution needs to clarify the following test case as well:
class C; //1
union {
class C { ... }; //2
...
};
Does line //2 defines the class declared on line //1?
Resolution:
Requestor: Tom Plum / Dan Saks
Owner: Steve Adamczyk (Types)
Emails:
Papers:
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Work Group: Core
Issue Number: 479
Title: How can typedefs be used to declare member functions?
Section: 9.2 [class.mem] class members
Status: active
Description:
Is this legal?
typedef void voidf(int);
class foo {
voidf vfunc; // legal? (unsure)
static voidf sfunc; // legal? (I think so)
};
The type of vfunc is certainly not voidf.
----------
Another example from Bill Gibbons:
struct A {
typedef void FTYPE();
void f();
FTYPE f1;
};
Do f and f1 have the same type?
----------
And how does this affect pointer to members?
More examples from Bill Gibbons:
struct T { void f(); };
typedef void F();
F T::*pmf = &T::f; // pointer to member function ?
// Bill's proposed answer yes.
struct T { void f(); };
typedef void (*PF)();
PF T::pmf = &T::f; // pointer to member function ?
// Bill's proposed answer no.
That is, once a declarator has been established to be a pointer to
member, the distinction of pointer to data member or pointer to
member function is entirely dependent on the type, not the syntax.
Resolution:
Requestor: Mike Ball
Owner: Steve Adamczyk (Types)
Emails:
core-5374, core-5447
Papers:
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Work Group: Core
Issue Number: 335
Title: Can unions contain reference members?
Section: 9.6 [class.union] Unions
Status: closed
Description:
union {
int *p;
int &r;
};
int i, i;
p = &i;
r = 1000;
Resolution:
See Monterey motion 4.
Requestor: John Armstrong
Owner: Steve Adamczyk (Unions)
Emails:
core-2028
Papers:
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Work Group: Core
Issue Number: 266
Title: Access specifiers in union member list
Section: 9.6 [class.union] Unions
Status: active
Description:
9.6p3.2 - anonymous union may not have private or protected members.
This seems to imply that anonymous union may have public members;
and that non-anonymous union may have any access modifiers.
Is this wording really what is intended?
Resolution:
Requestor: Tom Plum / Dan Saks
Owner: Steve Adamczyk (Unions)
Emails:
Papers:
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Work Group: Core
Issue Number: 105 (WMM.27)
Title: How can static members which are anon unions be initialized?
Section: 9.6 [class.union] Unions
Status: active
Description:
This is from Mike Miller's list of issues:
class C {
static union {
int i;
char * s;
};
union {
const int a, b;
};
};
int C::i = 3; // ? Is this syntax valid?
int C::a = 5; // ? Is this syntax valid?
Resolution:
Requestor: Mike Miller
Owner: Josee Lajoie (Initialization)
Emails:
Papers:
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Work Group: Core
Issue Number: 505
Title: Must anonymous unions declared in unnamed namespaces also be
declared static?
Section: 9.6 [class.union] Unions
Status: active
Description:
9.6p3 says:
"Anonymous unions declared at namespace scope shall be declared
static."
Must anonymous unions declared in unnamed namespaces also be
declared static? If the use of static is deprecated, this doesn't
make much sense.
Proposal:
Replace the sentence above with the following:
"Anonymous unions declared in a named namespace or in the global
namespace shall be declared static."
This is related to issue 526.
Resolution:
Requestor: Bill Gibbons
Owner: Josee Lajoie (linkage)
Emails:
Papers:
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Work Group: Core
Issue Number: 533
Title: Is an anonymous union a type?
Section: 9.6 [class.union] Unions
Status: active
Description:
9.6 paragraph 2 says: "... is called an anonymous union; it defines
an unnamed object (not a type)."
Is an anonymous union a type?
The sentence in paragraph 2 says it is an object with no type.
Doesn't this break the object model?
Resolution:
Requestor: Fergus Henderson
Owner: Josee Lajoie (object model)
Emails:
core-5893
Papers:
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Work Group: Core
Issue Number: 47
Title: enum bitfields - can they be declared with < bits than
required
Section: 9.7 [class.bit] Bitfields
Status: active
Description:
enum ee { one, two, three, four };
struct S {
ee bit:1; // allowed?
};
Resolution:
Requestor: ?
Owner: Steve Adamczyk (Declarators)
Emails:
core-1578
Papers:
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Work Group: Core
Issue Number: 267
Title: What does "Nor are there any references to bitfields" mean?
Section: 9.7 [class.bit] Bitfields
Status: active
Description:
9.7p3.5: "Nor are there references to bit-fields." Does this
actually prohibit anything? A simple attempt to make a reference
refer to a bit-field just creates a temporary:
union { int bitf:2; } u;
const int & r = u.bitf;
Or is this a syntactic restriction that prohibits something like
union { int (&rbitf):2 } u;
Or is it meant to prohibit the use of typedefs to attempt it, such as
union { typedef int bitf_t:2; bitf_t &rbitf; } u;
The intent needs clarifying.
Resolution:
Requestor: Tom Plum / Dan Saks
Owner: Steve Adamczyk (Declarators)
Emails:
Papers:
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Work Group: Core
Issue Number: 458
Title: When is an enum bitfield signed / unsigned?
Section: 9.7 [class.bit] Bitfields
Status: active
Description:
enum Bool { false=0, true=1 };
struct A {
Bool b:1;
};
A a;
a.b = true;
if (a.b == true) // if this is sign-extended, this fails.
Bill Gibbons proposed resolution:
Add after the sentence 9.7p5:
"It is implementation defined whether plain (neither explicitly
signed or unsigned) int bitfield is signed or unsigned."
"...; enumeration bit-fields are neither signed nor unsigned."
Resolution:
Requestor: Sam Kendall
Owner: Steve Adamczyk (Declarators)
Emails:
Papers:
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Work Group: Core
Issue Number: 525
Title: Implementation specific mapping of bitfields
Section: 9.7 [class.bit] Bitfields
Status: editorial?
Description:
9.7p1 says:
"1 Fields straddle allocation boundaries on some machines and not on
others. ... Fields are assigned right-to-left on some machines,
left-to-right on others.
2 An unnamed bit-field is useful for padding to conform to
externally imposed layouts.
"
These sentences are non-mormative, and should be moved as note or
footnote.
Resolution:
I would like to treat this as an editorial issue. Would there be any
objection?
Requestor: Sean Corfield
Owner: Josee Lajoie
Emails:
Papers:
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Work Group: Core
Issue Number: 68 (WMM.58)
Title: How do access control apply to members of nested classes in
the definition of the owning class?
Section: 9.8 [class.nest] Nested Class Declarations
Status: editorial?
Description:
From Mike Miller's list of issues:
How is access control applied to members of nested classes?
class X {
class Y { enum E { E1, E2 }; };
public:
Y::E f() { return Y::E1; } //1
};
Can Y::E be accessed as shown on line //1?
Can Y::E1 be accessed as shown on line //1?
The WP does not specify this.
9.8p2 says:
"Member functions of a nested class have no special access to members
of an enclosing class; they obey the usual access rules. Member
functions of an enclosing class have no special access to members
of a nested class; obey the usual access rules."
This should be changed to apply to more than just member functions...
This should be true for the entire scope of the enclosing or nested
class. For example:
"The scope of a nested class has no special access to members of an
enclosing class and the usual access rules shall be obeyed. The
scope of an enclosing class has no special access to members of a
nested class and the usual access rules shall be obeyed."
Resolution:
I would like to treat this as an editorial issue. Would there be any
objection?
Requestor: Mike Miller
Owner: Steve Adamczyk (Access Specifications)
Emails:
Papers:
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Work Group: Core
Issue Number: 27
Title: What is the access of nested class types declared multiple
times in the owning class definition?
Section: 9.8 [class.nest] Nested Class Declarations
Status: closed
Description:
struct ss {
public:
struct s;
union u;
class c;
protected:
struct s;
union u;
class c;
private:
struct s;
union u;
class c;
};
What is the accessibility of s, u, c?
Resolution:
See Monterey motion 2f.
Also see paper 95-0103/N0703.
Requestor: Ron Guilmette
Owner: Steve Adamczyk (Access Specifications)
Emails:
core-1517
Papers:
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
=============================================================================
Chapter 10 - Derived classes
------------------------------
Work Group: Core
Issue Number: 441
Title: In which scope is the base class clause looked up?
Section: 10 [class.derived] Derived classes
Status: active
Description:
class C {
class A { };
class B : A { }; //1
};
Is A looked up in the scope of C or in the scope of B?
Is the declaration on line //1 ill-formed because the nested class B
cannot refer to the private type A declared in C?
Or is it well-formed because the name A can be used in the scope of
C?
Resolution:
Requestor:
Owner: Steve Adamczyk (Name Lookup)
Emails:
Papers:
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Work Group: Core
Issue Number: 11
Title: How do retrictions on member mapping apply with multiple
inheritance?
Sections: 10.1 [class.mi] Multiple Base Classes
Status: editorial
Description:
10.1 paragraph 2 says that the order of derivation may be significant
to the storage layout. How do the restrictions described in 9.2
paragraph 11 relate to members declared in base classes?
Resolution:
Core 1 decided at the Monterey meeting that this is an editorial
issue.
Paragraph 2 should be a note.
Requestor: Scott Turner
Owner: Josee Lajoie (Object Model)
Emails:
core-1456
Papers:
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Work Group: Core
Issue Number: 442
Title: Can a class have a direct and an indirect base of the same
type?
Sections: 10.1 [class.mi] Multiple base classes
Status: editorial
Description:
class A { };
class B : public A { };
class C : public A, public B { };
Is this allowed?
Since class A's members can never be referred to, can an
implementation optimize the mapping for class C and not map the
direct base class A?
CFRONT omitted mapping the direct base class A.
Resolution:
Core 1 decided at the Monterey meeting that this is an editorial
issue.
The beginning of paragraph 3 should read as follows:
"A class shall not be specified as a direct base class of a derived
class more than once. [Note: a class can be an indirect base class
more than once and can be a direct and indirect base class."
Requestor:
Owner: Josee Lajoie (Object Model)
Emails:
Papers:
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Work Group: Core
Issue Number: 529
Title: Can two base class subobjects be allocated at the same
address?
Sections: 10.1 [class.mi] Multiple base classes
Status: active
Description:
struct B { void f(); };
struct L : B{};
struct R : B{};
struct D : L,R{};
Since B has no data members, can B have the same address as another
member subobject of of D?
That is, can a base class subobject have zero size?
Resolution:
Requestor: Bill Gibbons
Owner: Josee Lajoie (Object Model)
Emails:
Papers:
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Work Group: Core
Issue Number: 446
Title: Can explicit qualification be used for base class navigation?
Sections: 10.1 [class.mi] Multiple base classes
Status: active
Description:
Can explicit qualification be used for base class sublattice
navigation?
class A {
public:
int i;
};
class B : public A { };
class C : public B { };
class D {
public:
int i;
};
class E : public D { };
class F : public E { };
class Z : public C, public F { };
Z z;
... z.F::E::D::i; // is qualification allowed here to navigate the
// base class sublattice?
Resolution:
Requestor: Bill Gibbons
Owner: Steve Adamczyk (Name Lookup)
Emails:
Papers:
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Work Group: Core
Issue Number: 447
Title: When should a class without a final overrider be ill-formed?
Sections: 10.3 [class.virtual] Virtual Functions
Status: active
Description:
p7 shows:
struct A {
virtual void f();
};
struct B : virtual A {
void f();
};
struct C : virtual A {
void f();
};
struct E : B, C { }; //1
Is the declaration of E on line //1 ill-formed?
Why not wait until an object of class E is created to issue the error
message?
Making the declaration of E on line //1 ill-formed prevents programs
to further derive from E and override the virtual member function.
i.e.
struct F : E {
void f();
};
Resolution:
Requestor:
Owner: Josee Lajoie (Object Model)
Emails:
Papers:
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
=============================================================================
Chapter 11 - Member Access Control
------------------------------------
Work Group: Core
Issue Number: 22
Title: Must implementations respect access restrictions?
Section: 11.1 [class.access.spec] Access Specifiers
Status: active
Description:
What are the access restrictions used for?
Are they only limitations on what the programmer may write?
Must implementations also respect them for the compiler generated
code? (i.e. use of default and copy constructors, use of destructors
at the end of a block or at the end of the program).
And if implementations must respect access restriction, when must it
report the errors?
struct B {
private:
~B () { }
};
struct D : public B {
~D () { } // is the mere existence of D::~D considered an
// implicit call of B::~B and therefore a protection
// violation?
};
void f() {
D d; // Or is this an error?
} // Or is the error when d is destroyed?
Resolution:
Requestor: Jerry Schwarz
Owner: Josee Lajoie (Object Model)
Emails:
core-1525
Papers:
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Work Group: Core
Issue Number: 284
Title: access to base class ctor/dtor
Sections: 11.2 [class.access.base] Access Specifiers for Base Classes
Status: active
Description:
base access rules don't apply to non-inherited members
11.2 After much discussion, we believe that the intent is as follows:
"The members whose accessibility is described in this section are
only those members which are inherited from the base class; the
non-inherited members such as constructors, destructors, and
assignment operators are not subject to these accessibility rules."
I still have problems with this one. There are two separate issues,
one minor and one substantive. Minor issue: The ctor, dtor, and
assignment op of a base are not accessible as "members of the
derived class" (because they aren't inherited in the derived class),
but I believe that access restrictions still apply to them. So it's
just a job of re-wording 11.2/p1 to clarify this.
But the substantive issue is a real problem. The vagueness has been
unresolved so long that implementations have differed in the
treatment of access declarations upon base class ctors and dtors.
Could you discuss this with me and we'll determine how to proceed.
Resolution:
Requestor: Tom Plum / Dan Saks
Owner: Josee Lajoie (Object Model)
Emails:
Papers:
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Work Group: Core Language
Issue Number: 388
Title: Access Declarations and qualified ids
Section: 11.3 [class.access.dcl] Access Declarations
Status: active
Description:
The section says:
The base class member is given, in the derived class, the access in
effect in the derived class declaration at the point of the access
declaration.
It isn't clear to me what this means for
class B { public: int i ; } ;
class D : private B {
B::i ;
};
D* p ;
p->i ; // clearly legal
p->B::i ;
I don't care strongly about this, but I think it should be clarified.
(And added as an example).
Resolution:
Requestor: Jerry Schwarz
Owner: Steve Adamczyk (Access Specifications)
Emails:
Papers:
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Work Group: Core
Issue Number: 448
Title: Can '::' be used to declare global functions as friends?
Section: 11.4 [class.friend] Friends
Status: active
Description:
Should it be allowed to prefix the declarator of a friend
function declaration with '::' to indicate that a global
function is the friend?
void f();
class C {
void f();
friend void ::f();
};
or
class B {
void f();
};
class C {
class B { };
friend void ::B::f();
};
Resolution:
Requestor:
Owner: Steve Adamczyk (Name Lookup)
Emails:
Papers:
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Work Group: Core
Issue Number: 515
Title: How can friend classes use private and protected names?
Section: 11.4 [class.friend] Friends
Status: active
Description:
11.4 p2 says:
"Declaring a class to be a friend implies that private and protected
names from the class granting friendship can be used in the class
receiving it."
This is not very explicit.
Where can the private and protected names be used in the befriended
class?
In the base classes of the befriended class?
In the nested classes of the befriended class?
Resolution:
Requestor: Erwin Unruh
Owner: Steve Adamczyk (Friends)
Emails:
Papers:
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Work Group: Core
Issue Number: 532
Title: Is a complete class definition allowed in a friend
declaration
Section: 11.4 [class.friend]
Status: active
Description:
Is this allowed:
class A {
static int x;
friend class B {
int f() { return A::x; };
};
};
If so, what is the scope of the class name B?
Resolution:
Requestor: Neal M Gafter <gafter@mri.com>
Owner: Steve Adamczyk (Friends)
Emails:
Papers:
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Work Group: Core
Issue Number: 449
Title: restriction on protected member access should not apply to
types, static members, and member constants
Section: 11.5 [class.protected] Protected member access
Status: closed
Description:
P1 of 11.5 now implies that:
class C {
protected:
int i;
static int j;
};
class D : public C {
void f();
};
void D::f() {
C::i = 4; //OK, implied 'this' pointer, qualification ignored
C::j = 6; //error, nested-name-specifier must represent the
// derived class
}
The rules for static and nonstatic members should be as uniform as
possible. In particular, changing a member from static to non-static
or vice-versa should have no effect on the whether the program
violates any access rules.
But this isn't so in the proposed set of rules.
Since we don't want to break the "implicit this" rules, I think the
only solution is to allow friends and members of the derived class
to access static members of the base class with a base class
qualifier. That is, apply the access rules as if the member were
nonstatic. This change would make the second line in the above
example well-form
----------
Steve Adamczyk in core-5598:
11.5 [class.protected] says:
"A friend or a member function of a derived class can access a
protected static member, type or enumerator constant of a base
class; if the access is through a qualified-id, the
nested-name-specifier must name the derived class (or any class
derived from that class)."
I remember that when the wording for the qualified-id case was added
a few years back, the issue being addressed was pointers-to-members
(exclusively).
Where it used to be clear in the ARM that this additional protected
member access check applied only to nonstatic members, and therefore
not to types, member constants, and static members, now the wording
has made it clear that the check IS done for those.
If you read the commentary in the ARM, you see why this check is
useful, and the problems being prevented don't apply to static
members etc. I think this is just a mistake that's spreading.
Resolution:
See motion 2g.
Requestor: Bill Gibbons
Owner: Steve Adamczyk (Access Specifications)
Emails:
Papers:
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
=============================================================================
Chapter 12 - Special Member functions
---------------------------------------
Work Group: Core
Issue Number: 379
Title: Invoking member functions which are "not inherited".
Section: 12.1 [class.ctor] Constructors
12.4 [class.dtor] Destructors
12.8 [class.copy] Class Copy
Status: active
Description:
Section 5.1/8 of the 1/93 working paper says:
"A nested-class-specifier (9.1) followed by :: and the name
of a member of that class (9.2) or a member of a base of
that class (10) is a qualified-id; its type is the type of
the member. The result is the member."
Section 12.1/1 says:
"Constructors are not inherited."
Section 12.4/6 says:
"Destructors are not inherited."
May a member of a given base class type which is "not inherited" by
another class type (derived from the given base class type) be
invoked for an object whose static type is the derived class type if
the invocation is done using the class-qualified name syntax? If,
not, is an implementation obliged to issue a compile-time diagnostic
for such usage?
Is the behavior "well defined" if an attempt is made to invoke a
non-inherited member for an object whose static type is that of the
base class but whose dynamic type is that of the derived class?
struct B {
virtual ~B () { }
};
struct D : public B {
~D () { }
};
D D_object;
D D_object2;
B *B_ptr = &D_object2;
void caller ()
{
D_object.B::~B(); // ok?
B_ptr->~B(); // ok?
}
Resolution:
Requestor: Ron Guilmette
Owner: Josee Lajoie (Special member functions)
Emails:
Papers:
94-0193R1/N0580
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Work Group: Core
Issue Number: 477
Title: When can an implementation create temporaries?
Section: 12.2 [class.temporary]
Status: editorial
Description:
12.2[class.temporary]/2 still contains the phrase
"In some circumstances it might be necessary or convenient for an
implementation to generate a temporary object. Precisely when such
temporaries are introduced is implementation-defined".
This seems extremely vague. For example, is the implementation
allows to introduce a temporary in the following example?
class Foo { };
int main() {
return 0;
}
Can the temporary be of type `Foo'?
If `Foo' had a private constructor, could the implementation
introduce a temporary of type `Foo', and then reject the program as
ill-formed??
(Perhaps the answers to these questions are obvious, but I don't
think they are obvious from the text in the working paper.)
Proposal:
Change the sentences above to say:
"While evaluating an expression, it might be necessary or
convenient for an implementation to generate temporary objects to
hold values resulting from the evaluation of the expression's
subexpressions. During this evaluation, precisely when such
temporaries are introduced is unspecified."
Resolution:
Core 1 decided at the Monterey meeting that this is an editorial
issue.
Requestor: Fergus Henderson
Owner: Josee Lajoie (Temporaries)
Emails:
core-5542
Papers:
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Work Group: Core
Issue Number: 516
Title: What is the lifetime of "helping" temporaries?
Section: 12.2 [class.temporary]
Status: closed
Description:
12.2p4 says:
"The first context is when an expression appears as an initializer
for a declarator defining an object. In that context, the temporary
that holds the result of the expression shall persist until the
object's intialization is complete."
All temporaries created in the evaluation of the expression should
last until the object is initialized. It should NOT be limited to
the result temporary. For example:
char *a = string().c_str;
12.2p5 says:
"The temporary bound to a reference or the temporary containing the
sub-object that is bound to the reference persists for the lifetime
of the reference initialized..."
It should be made explicit, whether helping references also last as
long as the reference.
char * &ra = string().c_str;
Does the string temporary last as long as the reference?
Resolution:
Core 1 decided at the Monterey meeting that the WP text was already
clear.
Requestor: Erwin Unruh
Owner: Josee Lajoie (Temporaries)
Emails:
Papers:
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Work Group: Core
Issue Number: 507
Title: Must a temporary initializing an object be destroyed _as
soon as_ it has been copied?
Section: 12.2 [class.temporary]
Status: editorial
Description:
12.2p4 says:
"The object is initialized from a copy of the temporary; during this
copying, an implementation can call the copy constructor many
times; the temporary is destroyed as soon as it has been copied."
Bill says:
don't recall the requirement of "as soon as it has been copied";
I thought it was any time before the end of the initialization.
Proposal:
Change the sentence above to:
"... the temporary shall be destroyed after it has been copied,
before or when the initialization completes."
Resolutions:
Core 1 decided at the Monterey meeting that this is an editorial
issue.
Requestor: Bill Gibbons
Owner: Josee Lajoie (Temporaries)
Emails:
Papers:
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Work Group: Core Language
Issue Number: 509
Title: How does "destroy in reverse order of creation" work for
temporaries bound to references vs temporaries destroyed at
the end of the initialization?
Section: 12.2 [class.temporary]
Status: editorial
Description:
12.2p6:
"In all cases, temporaries are destroyed in reverse order of
creation."
There is an exception to "reverse order of creation":
Temporaries are destroyed in reverse order of creation,
except those temporaries created in an expression used
to initialize a reference; these are destroyed when
the reference is destroyed, in reverse order of creation.
Proposal:
Add at the end of paragraph 4:
"If many temporaries are created during an object's initialization,
these temporaries are destroyed in reverse order of creation."
Add at the end of paragraph 5:
"Temporaries bound to references are destroyed in reverse order of
creation."
Delete paragraph 6.
Resolution:
Core 1 decided at the Monterey meeting that this is an editorial
issue.
Requestor: Bill Gibbons
Owner: Josee Lajoie (Temporaries)
Emails:
Papers:
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Work Group: Core Language
Issue Number: 347
Title: Limitations on declarations of user-defined type-conversions.
Section: 12.3.2 [class.conv.fct] Conversion functions
Status: active
Description:
Given a declaration such as:
struct S {
operator T ();
};
... where `T' is a typedef name declared in an earlier typedef
declaration, must a standard conforming implementation issue a
diagnostic for the declaration of the type conversion operator (as
shown above) if, at the point of declaration of the type conversion
operator itself, the type T is:
o A complete array type?
o An incomplete array type?
o An incomplete class type?
o A function type?
Resolution:
Requestor: Ron Guilmette
Owner: Steve Adamczyk (Type Conversions)
Emails:
Papers:
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Work Group: Core Language
Issue Number: 485
Title: Order of destruction of base classes and members
Section: 12.4 [class.dtor] Destructors
Status: editorial
Description:
12.4p5 says:
"Bases and members are destroyed in reverse order of their
construction."
Since construction takes place over time, is the order that is to be
reversed the one when the constructor begins or when it finishes.
Jerry's proposed answer:
The one when it finishes.
Resolution:
Core 1 decided at the Monterey meeting that this is an editorial
issue.
Requestor: Jerry Schwarz
Owner: Josee Lajoie (Destruction)
Emails:
core-5596
Papers:
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Work Group: Core
Issue Number: 293
Title: Clarify the meaning of y.~Y
Section: 12.4 [class.dtor] Destructors
Status: active
Description:
Resolution:
12.4p22 The notation y.~Y() is explicitly approved of by the example
at bottom of ARM page 279), but nothing in the draft gives this
explicit approval. Implementations differ. Committee should
approve it or disapprove it.
Requestor: Tom Plum / Dan Saks
Owner: Josee Lajoie (Destruction)
Emails:
Papers:
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Work Group: Core
Issue Number: 508
Title: When is a destructor implicitly-defined?
Section: 12.4 [class.dtor] Destructors
Status: editorial
Description:
12.4p4 says:
"An implicitly-declared destructor is implicitly defined when it is
used to destroy an object of its class type."
When is a destructor used?
add a footnote to say:
"Destructors are called implicitly not only when an object of
automatic storage duration goes out of scope, or at the end of a
program for objects with static storage duration, but also in
several situations due to the handling of exceptions."
Resolution:
Core 1 decided at the Monterey meeting that this is an editorial
issue.
Requestor: Bill Gibbons
Owner: Josee Lajoie (Destruction)
Emails:
Papers:
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Work Group: Core
Issue Number: 450
Title: How is a class operator new/delete looked up?
Section: 12.5 [class.free] Free Store
Status: closed
Description:
[class.free] says:
"2 When a non-array object or an array of class T is created by a
new-expression, the allocation function is looked up in the scope
of class T using the usual rules."
Does that mean that operator new is looked up as a member of T and
then in the current scope, or that it is looked up as a member of T
and then in the enclosing scope of T? In other words, is this code
well-formed?
struct A { };
struct B {
char buf[sizeof (A)];
void *operator new (size_t, void *p, int) { return p; }
B() { new (buf, 1) A; }
};
How about this?
namespace foo {
void *operator new (size_t, void *p, int) { return p; }
struct A { };
}
namespace bar {
struct B {
char buf[sizeof (foo::A)];
B() { new (buf, 1) foo::A; }
};
}
At the Austin (March 95) meeting:
Neal Gafter answered this issue by saying:
(see 95-0063R1/N0663R1)
"This is already answered by the current WP.
Specifically, operator new is looked up in the scope of the class,
then globally (WP 12.5 [class.free] p2). Operator delete is looked
up both from the point of the delete expression (p7) and from the
destructor(p10)."
[ Note JL: ]
First, I believe the wording in 12.5 could be made clearer to say
"looked up in the class scope and then globally".
Second, in the light of the new function overload resolution rules
which say that an operator is looked up in a namespace scope N if
it is used with an operand of type class C declared in namespace N,
(see 13.3.1.2 [over.match,oper] p3 and 4), do we want this to be
true for new and delete operators (with placement) as well?
i.e. if an operator new with placement is used to create an object
of type C and C is defined in namescope N, will the scope of
namespace N be searched to find an appropriate operator new with
placement? i.e. do we want to make Jason's 2nd example work?
If we want this to be true, then I believe the wording in 12.5 needs
work.
Resolution:
See Monterey motion 9.
Also see paper 95-0148R1/N0748R1.
Requestor: Jason Merrill
Owner: Steve Adamczyk (Name lookup)
Emails:
core-4749
Papers:
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Work Group: Core
Issue Number: 138 (WMM.89)
Title: When are default ctor default args evaluated for array
elements?
Section: 12.6 [class.init] Initialization
Status: active
Description:
From Mike Miller's list of issues.
WMM.89. Are default constructor arguments evaluated for each element
of an array or just once for the entire array?
int count = 0;
class T {
int i;
public:
T ( int j = count++ ) : i ( j ) {}
~T () { printf ( "%d,%d\n", i, count ); }
};
T arrayOfTs[ 4 ];
Should this produce the output :-
0,4
1,4
2,4
3,4
or should it produce :-
0,1
0,1
0,1
0,1
Resolution:
Requestor: Mike Miller / Martin O'Riordan
Owner: Josee Lajoie (Initialization)
Emails:
core-668
Papers:
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Work Group: Core Language
Issue Number: 359
Title: Timing of Evaluations in Base and Member Initializations
Section: 12.6.2 [class.base.init] Initializing Bases and Members
Status: closed
Description:
Section 12.6.2 describes the order in which the members and base
class parts of an object of class type are initialized. It does not,
however, specify when the expressions used in the "mem-initializers"
are to be evaluated.
Consider this example:
struct S {
int i;
int j;
S() : i(0), j(i) {}
};
12.6.2/1 requires that i be initialized before j. But it seems to
permit this order of execution:
- Fetch the (uninitialized) value of i
- Initialize i to 0
- Initialize j to the previously fetched value of i
which is probably not what the programmer intended.
Here, there is no function call (constructor call) to initialize the
member i, is there none-the-less a sequence point after i is
initialized?
I would suggest adding words similar to:
The expressions in the expression-list part of a
mem-initializer are evaluated (including all side effects)
immediately before the corresponding initialization is
performed. When one base class or member is initialized
before another base class or member, the expressions used in
the mem-initializer for the second are evaluated (including
all side effects) after the first initialization is
performed.
Resolution:
See Monterey motion 2b.
Requestor: Patrick Smith
Owner: Josee Lajoie (Initialization)
Emails:
Papers:
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Work Group: Core Language
Issue Number: 534
Title: Can the members of an anonymous union be named in a
ctor-initializer?
Section: 12.6.2 [class.base.init] Initializing Bases and Members
Status: active
Description:
struct X {
union { int i; float f; };
X() : f(1.0); // Is this valid?
};
Resolution:
Requestor: Fergus Henderson
Owner: Josee Lajoie (Initialization)
Emails:
core-5893
Papers:
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Work Group: Core
Issue Number: 478
Title: can a union constructor initialize multiple members?
Section: 12.6.2 [class.base.init] Initializing Bases and Members
Status: active
Description:
can a union constructor initialize multiple members?
Resolution:
Requestor: Neal Gafter
Owner: Josee Lajoie (Initialization)
Emails:
Papers:
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Work Group: Core
Issue Number: 95
Title: Volatility, copy constructors, and assignment operators.
Section: 12.8 [class.copy]
Status: active
Description:
It appears that volatile qualification has been overlooked in the
specification of copy constructors and assignment operators.
Section 12.1p5 of the WP says:
"A copy constructor for a class X is a constructor whose first
argument is of type X& or const X&..."
But a user should be able to pass volatile objects (by reference) to
copy constructors and/or assignment operators.
In such cases it would be useful (and symmetric with const
qualification) if:
(a) these objects could be used as arguments to copy constructors and
assignment operators, and
(b) if the volatility associated with the types of the objects were
preserved in the process.
Resolution:
Requestor: Ron Guilmette
Owner: Josee Lajoie (Special Member Functions)
Emails:
core-1653
Papers:
See paper 95-0056/N0656
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=============================================================================
Chapter 13 - Overloading
--------------------------
Work Group: Core
Issue Number: 451
Title: Description of a call to a member function through a pointer
to member is missing
Section: 13.2.1.1.1 [over.call.func] Call to named function
Status: active
Description:
Should this section also describe calls to member functions using the
pointer to member syntax (.*, ->*) ?
Resolution:
Requestor:
Owner: Steve Adamczyk (function overload resolution)
Emails:
Papers:
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Work Group: Core
Issue Number: 517
Title: Candidate operator functions for built-in operators do not
cover the type bool appropriately
Section: 13.6 [over.built] Built-in operators
Status: closed
Description:
The type bool is not sufficiently represented. This is most visible
for ++ and --, which is different for type bool.
Resolution:
See Monterey motion 2j.
Requestor: Erwin Unruh
Owner: Steve Adamczyk (function overload resolution)
Emails:
Papers:
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Work Group: Core
Issue Number: 518
Title: The candidate operator function for built-in operator= for
pointer to members is missing
Section: 13.6 [over.built] Built-in operators
Status: closed
Description:
The candidate operator function for built-in operator= for pointer
to members is missing.
Resolution:
See Monterey motion 2j.
Requestor: Erwin Unruh
Owner: Steve Adamczyk (function overload resolution)
Emails:
Papers:
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
=============================================================================
Chapter 15 - Exception Handling
---------------------------------
Work Group: Core
Issue Number: 539
Title: Can one throw a pointer-to-member to a base class and catch
it with a handler taking a pointer to a derived class?
Section: 15.3 [except.handle] Handling an exception
Status: active
Description:
struct B { int i; };
struct D : B { };
int B::*pmb;
void f() {
try {
throw pmb;
}
catch (int D::*pmd) {
// is the exception handled here?
}
catch(...) {
// or here?
}
}
Resolution:
Requestor:
Owner: Bill Gibbons (exceptions)
Emails:
Papers:
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Work Group: Core
Issue Number: 540
Title: How does name look up proceed in a function-try-block?
Section: 15.3 [except.handle] Handling an exception
Status: active
Description:
Can names of variables declared in the outermost block of the
function be referred to?
If the function-try-block appears in a member function definition,
are names declared in the scope of the class considered?
Resolution:
Requestor:
Owner: Bill Gibbons (exceptions)
Emails:
Papers:
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Work Group: Core
Issue Number: 541
Title: Is a function-try-block allowed for the function main?
Section: 15.3 [except.handle] Handling an exception
Status: active
Description:
I assume the new syntax that allows for function-try-block is also
allowed if the function is main:
main()
try {
}
catch (...) { }
What is the effect of the catch(...) in main if the constructor for
an object with static storage duration throws an exception (and the
constructor does not catch the exception)?
Because the WP does not dictate a precise moment for the construction
of objects with static storage duration (these objects can be
constructed at any time before the first statement in main or...), is
it implementation-defined whether the handler in main catch an
exception thrown from a constructor for a global static object? Or
is the catch in main guaranteed to catch (or guaranteed not to catch)
such an exception?
Resolution:
Requestor:
Owner: Bill Gibbons (exceptions)
Emails:
Papers:
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Work Group: Core
Issue Number: 542
Title: What exception can a reference to a pointer to base catch?
Section: 15.3 [except.handle] Handling an exception
Status: active
Description:
15.3 says:
A handler with type T, const T, T&, or const T& is a match for a
throw-expression with an object of type E if
...
[3] T is a pointer type and E is a pointer type that can be
converted to T by a standard conversion.
This allows code like this:
struct A { };
struct B { };
struct D : A, B { };
D d;
try {
D* pd = new D;
throw pd;
}
catch (B*& pb) {// OK, B*& is a valid handler
// for a throw of type D*
}
However, code equivalent to this outside of the exception handling
try/catch mechanism is disallowed, i.e.
B*& pb = new D; // error
The current language rules (8.5.3) require that the reference be of
const type for this initialization to be valid. i.e.
B* const & pb = new D; // OK
preventing the pointer referred to by the reference from being
modified with the value of a pointer of a different type.
Going back to the original example with EH, 15.3 allows someone to
write code as follows in the handler, code which modifies the
original exception thrown:
catch (B*& pb) {
pb = new B;
}
Allowing this doesn't seem to make much sense to me because if the
program ever tries to refer to the original exception thrown as a D*
after the assignment to pb has taken place (using a rethrow, for
example) undefined behavior is almost guaranteed to take place i.e.
the exception of type D* has become an object of type B* and the type
system has been completely bypassed.
I believe 15.3 should say that a handler with type T& is _not_ a
match for a throw-expression with an object of type E if T and E are
pointer types that are not of the same types.
There may be other adjustments needed as well to make 15.3 mimic more
closely the rules on reference initialization.
Resolution:
Requestor:
Owner: Bill Gibbons (exceptions)
Emails:
Papers:
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
=============================================================================
Chapter 16 - Preprocessing Directives
---------------------------------------