| Doc. no. | J16/01-0006 = WG21 N1292 |
| Date: | 20 Mar 2001 |
| Project: | Programming Language C++ |
| Reply to: | Matt Austern <austern@research.att.com> |
Reference ISO/IEC IS 14882:1998(E)
Also see:
This document contains only library issues which have been closed by the Library Working Group (LWG) after being found to be defects in the standard. That is, issues which have a status of DR, TC, or RR. See "C++ Standard Library Closed Issues List" for issues closed as non-defects. See the "C++ Standard Library Active Issues List" for active issues and more information. The introductory material in that document also applies to this document.
Section: 17.4.2.2 [lib.using.linkage] Status: DR Submitter: Beman Dawes Date: 16 Nov 1997
The change specified in the proposed resolution below did not make it into the Standard. This change was accepted in principle at the London meeting, and the exact wording below was accepted at the Morristown meeting.
Proposed resolution:
Change 17.4.2.2 [lib.using.linkage] paragraph 2 from:
It is unspecified whether a name from the Standard C library declared with external linkage has either extern "C" or extern "C++" linkage.
to:
Whether a name from the Standard C library declared with external linkage has extern "C" or extern "C++" linkage is implementation defined. It is recommended that an implementation use extern "C++" linkage for this purpose.
Section: 18.3 [lib.support.start.term] Status: DR Submitter: Steve Clamage Date: 12 Dec 1997
We appear not to have covered all the possibilities of
exit processing with respect to
atexit registration.
Example 1: (C and C++)
#include <stdlib.h>
void f1() { }
void f2() { atexit(f1); }
int main()
{
atexit(f2); // the only use of f2
return 0; // for C compatibility
}
At program exit, f2 gets called due to its registration in main. Running f2 causes f1 to be newly registered during the exit processing. Is this a valid program? If so, what are its semantics?
Interestingly, neither the C standard, nor the C++ draft standard nor the forthcoming C9X Committee Draft says directly whether you can register a function with atexit during exit processing.
All 3 standards say that functions are run in reverse order of their registration. Since f1 is registered last, it ought to be run first, but by the time it is registered, it is too late to be first.
If the program is valid, the standards are self-contradictory about its semantics.
Example 2: (C++ only)
void F() { static T t; } // type T has a destructor
int main()
{
atexit(F); // the only use of F
}
Function F registered with atexit has a local static variable t, and F is called for the first time during exit processing. A local static object is initialized the first time control flow passes through its definition, and all static objects are destroyed during exit processing. Is the code valid? If so, what are its semantics?
Section 18.3 "Start and termination" says that if a function F is registered with atexit before a static object t is initialized, F will not be called until after t's destructor completes.
In example 2, function F is registered with atexit before its local static object O could possibly be initialized. On that basis, it must not be called by exit processing until after O's destructor completes. But the destructor cannot be run until after F is called, since otherwise the object could not be constructed in the first place.
If the program is valid, the standard is self-contradictory about its semantics.
I plan to submit Example 1 as a public comment on the C9X CD, with a recommendation that the results be undefined. (Alternative: make it unspecified. I don't think it is worthwhile to specify the case where f1 itself registers additional functions, each of which registers still more functions.)
I think we should resolve the situation in the whatever way the C committee decides.
For Example 2, I recommend we declare the results undefined.
[See reflector message lib-6500 for further discussion.]
Proposed resolution:
Change section 18.3/8 from:
First, objects with static storage duration are destroyed and functions registered by calling atexit are called. Objects with static storage duration are destroyed in the reverse order of the completion of their constructor. (Automatic objects are not destroyed as a result of calling exit().) Functions registered with atexit are called in the reverse order of their registration. A function registered with atexit before an object obj1 of static storage duration is initialized will not be called until obj1's destruction has completed. A function registered with atexit after an object obj2 of static storage duration is initialized will be called before obj2's destruction starts.
to:
First, objects with static storage duration are destroyed and functions registered by calling atexit are called. Non-local objects with static storage duration are destroyed in the reverse order of the completion of their constructor. (Automatic objects are not destroyed as a result of calling exit().) Functions registered with atexit are called in the reverse order of their registration, except that a function is called after any previously registered functions that had already been called at the time it was registered. A function registered with atexit before a non-local object obj1 of static storage duration is initialized will not be called until obj1's destruction has completed. A function registered with atexit after a non-local object obj2 of static storage duration is initialized will be called before obj2's destruction starts. A local static object obj3 is destroyed at the same time it would be if a function calling the obj3 destructor were registered with atexit at the completion of the obj3 constructor.
Rationale:
See 99-0039/N1215, October 22, 1999, by Stephen D. Clamage for the analysis supporting to the proposed resolution.
Section: 21.3.6.8 [lib.string::compare] Status: DR Submitter: Jack Reeves Date: 11 Dec 1997
At the very end of the basic_string class definition is the signature: int compare(size_type pos1, size_type n1, const charT* s, size_type n2 = npos) const; In the following text this is defined as: returns basic_string<charT,traits,Allocator>(*this,pos1,n1).compare( basic_string<charT,traits,Allocator>(s,n2);
Since the constructor basic_string(const charT* s, size_type n, const Allocator& a = Allocator()) clearly requires that s != NULL and n < npos and further states that it throws length_error if n == npos, it appears the compare() signature above should always throw length error if invoked like so: str.compare(1, str.size()-1, s); where 's' is some null terminated character array.
This appears to be a typo since the obvious intent is to allow either the call above or something like: str.compare(1, str.size()-1, s, strlen(s)-1);
This would imply that what was really intended was two signatures int compare(size_type pos1, size_type n1, const charT* s) const int compare(size_type pos1, size_type n1, const charT* s, size_type n2) const; each defined in terms of the corresponding constructor.
Proposed resolution:
Replace the compare signature in 21.3 [lib.basic.string] (at the very end of the basic_string synopsis) which reads:
int compare(size_type pos1, size_type n1,
const charT* s, size_type n2 = npos) const;
with:
int compare(size_type pos1, size_type n1,
const charT* s) const;
int compare(size_type pos1, size_type n1,
const charT* s, size_type n2) const;
Replace the portion of 21.3.6.8 [lib.string::compare] paragraphs 5 and 6 which read:
int compare(size_type pos, size_type n1,
charT * s, size_type n2 = npos) const;
Returns:
basic_string<charT,traits,Allocator>(*this, pos, n1).compare(
basic_string<charT,traits,Allocator>( s, n2))
with:
int compare(size_type pos, size_type n1,
const charT * s) const;
Returns:
basic_string<charT,traits,Allocator>(*this, pos, n1).compare(
basic_string<charT,traits,Allocator>( s ))
int compare(size_type pos, size_type n1,
const charT * s, size_type n2) const;
Returns:
basic_string<charT,traits,Allocator>(*this, pos, n1).compare(
basic_string<charT,traits,Allocator>( s, n2))
Editors please note that in addition to splitting the signature, the third argument becomes const, matching the existing synopsis.
Rationale:
While the LWG dislikes adding signatures, this is a clear defect in the Standard which must be fixed. The same problem was also identified in issues 7 (item 5) and 87.
Section: 21 [lib.strings] Status: DR Submitter: Matt Austern Date: 15 Dec 1997
(1) In 21.3.5.4 [lib.string::insert], the description of template <class InputIterator> insert(iterator, InputIterator, InputIterator) makes no sense. It refers to a member function that doesn't exist. It also talks about the return value of a void function.
(2) Several versions of basic_string::replace don't appear in the class synopsis.
(3) basic_string::push_back appears in the synopsis, but is never described elsewhere. In the synopsis its argument is const charT, which doesn't makes much sense; it should probably be charT, or possible const charT&.
(4) basic_string::pop_back is missing.
(5) int compare(size_type pos, size_type n1, charT* s, size_type n2 = npos) make no sense. First, it's const charT* in the synopsis and charT* in the description. Second, given what it says in RETURNS, leaving out the final argument will always result in an exception getting thrown. This is paragraphs 5 and 6 of 21.3.6.8 [lib.string::compare]
(6) In table 37, in section 21.1.1 [lib.char.traits.require], there's a note for X::move(s, p, n). It says "Copies correctly even where p is in [s, s+n)". This is correct as far as it goes, but it doesn't go far enough; it should also guarantee that the copy is correct even where s in in [p, p+n). These are two orthogonal guarantees, and neither one follows from the other. Both guarantees are necessary if X::move is supposed to have the same sort of semantics as memmove (which was clearly the intent), and both guarantees are necessary if X::move is actually supposed to be useful.
Proposed resolution:
ITEM 1: In 21.3.5.4 [lib.string::insert], change paragraph 16 to
EFFECTS: Equivalent to insert(p - begin(), basic_string(first, last)).
ITEM 2: Not a defect; the Standard is clear.. There are ten versions of replace() in
the synopsis, and ten versions in 21.3.5.6 [lib.string::replace].
ITEM 3: Change the declaration of push_back in the string synopsis (21.3,
[lib.basic.string]) from:
void push_back(const charT)
to
void push_back(charT)
Add the following text immediately after 21.3.5.2 [lib.string::append], paragraph 10.
void basic_string::push_back(charT c);
EFFECTS: Equivalent to append(static_cast<size_type>(1), c);
ITEM 4: Not a defect. The omission appears to have been deliberate.
ITEM 5: Duplicate; see issue 5 (and 87).
ITEM 6: In table 37, Replace:
"Copies correctly even where p is in [s, s+n)."
with:
"Copies correctly even where the ranges [p, p+n) and [s,
s+n) overlap."
Section: 22.1.1.5 [lib.locale.statics] Status: DR Submitter: Matt Austern Date: 24 Dec 1997
It appears there's an important guarantee missing from clause 22. We're told that invoking locale::global(L) sets the C locale if L has a name. However, we're not told whether or not invoking setlocale(s) sets the global C++ locale.
The intent, I think, is that it should not, but I can't find any such words anywhere.
Proposed resolution:
Add a sentence at the end of 22.1.1.5 [lib.locale.statics], paragraph 2:
No library function other than locale::global() shall affect the value returned by locale().
Section: 18.4.1 [lib.new.delete] Status: DR Submitter: Steve Clamage Date: 4 Jan 1998
Scott Meyers, in a comp.std.c++ posting: I just noticed that section 3.7.3.1 of CD2 seems to allow for the possibility that all calls to operator new(0) yield the same pointer, an implementation technique specifically prohibited by ARM 5.3.3.Was this prohibition really lifted? Does the FDIS agree with CD2 in the regard? [Issues list maintainer's note: the IS is the same.]
Proposed resolution:
Change the last paragraph of 3.7.3 from:
Any allocation and/or deallocation functions defined in a C++ program shall conform to the semantics specified in 3.7.3.1 and 3.7.3.2.
to:
Any allocation and/or deallocation functions defined in a C++ program, including the default versions in the library, shall conform to the semantics specified in 3.7.3.1 and 3.7.3.2.
Change 3.7.3.1/2, next-to-last sentence, from :
If the size of the space requested is zero, the value returned shall not be a null pointer value (4.10).
to:
Even if the size of the space requested is zero, the request can fail. If the request succeeds, the value returned shall be a non-null pointer value (4.10) p0 different from any previously returned value p1, unless that value p1 was since passed to an operator delete.
5.3.4/7 currently reads:
When the value of the expression in a direct-new-declarator is zero, the allocation function is called to allocate an array with no elements. The pointer returned by the new-expression is non-null. [Note: If the library allocation function is called, the pointer returned is distinct from the pointer to any other object.]
Retain the first sentence, and delete the remainder.
18.4.1 currently has no text. Add the following:
Except where otherwise specified, the provisions of 3.7.3 apply to the library versions of operator new and operator delete.
To 18.4.1.3, add the following text:
The provisions of 3.7.3 do not apply to these reserved placement forms of operator new and operator delete.
Rationale:
See 99-0040/N1216, October 22, 1999, by Stephen D. Clamage for the analysis supporting to the proposed resolution.
Section: 23.3.5 [lib.template.bitset] Status: DR Submitter: Matt Austern Date: 22 Jan 1998
(1) bitset<>::operator[] is mentioned in the class synopsis (23.3.5), but it is not documented in 23.3.5.2.
(2) The class synopsis only gives a single signature for bitset<>::operator[], reference operator[](size_t pos). This doesn't make much sense. It ought to be overloaded on const. reference operator[](size_t pos); bool operator[](size_t pos) const.
(3) Bitset's stream input function (23.3.5.3) ought to skip all whitespace before trying to extract 0s and 1s. The standard doesn't explicitly say that, though. This should go in the Effects clause.
Proposed resolution:
ITEMS 1 AND 2:
In the bitset synopsis (23.3.5 [lib.template.bitset]),
replace the member function
reference operator[](size_t pos);
with the two member functions
bool operator[](size_t pos) const;
reference operator[](size_t pos);
Add the following text at the end of 23.3.5.2 [lib.bitset.members],
immediately after paragraph 45:
bool operator[](size_t pos) const;
Requires: pos is valid
Throws: nothing
Returns: test(pos)
bitset<N>::reference operator[](size_t pos);
Requires: pos is valid
Throws: nothing
Returns: An object of type bitset<N>::reference such that (*this)[pos] == this->test(pos), and such that (*this)[pos] = val is equivalent to this->set(pos, val);
Rationale:
The LWG believes Item 3 is not a defect. "Formatted input" implies the desired semantics. See 27.6.1.2 [lib.istream.formatted].
Section: 27.6.1.2.3 [lib.istream::extractors] Status: DR Submitter: William M. Miller Date: 3 Mar 1998
In 27.6.1.2.3, there is a reference to "eos", which is the only one in the whole draft (at least using Acrobat search), so it's undefined.
Proposed resolution:
In 27.6.1.2.3 [lib.istream::extractors], replace "eos" with "charT()"
Section: 22.1.1.3 [lib.locale.members] Status: DR Submitter: Nathan Myers Date: 6 Aug 1998
locale::combine is the only member function of locale (other than constructors and destructor) that is not const. There is no reason for it not to be const, and good reasons why it should have been const. Furthermore, leaving it non-const conflicts with 22.1.1 paragraph 6: "An instance of a locale is immutable."
History: this member function originally was a constructor. it happened that the interface it specified had no corresponding language syntax, so it was changed to a member function. As constructors are never const, there was no "const" in the interface which was transformed into member "combine". It should have been added at that time, but the omission was not noticed.
Proposed resolution:
In 22.1.1 [lib.locale] and also in 22.1.1.3 [lib.locale.members], add "const" to the declaration of member combine:
template <class Facet> locale combine(const locale& other) const;
Section: 22.1.1.3 [lib.locale.members] Status: DR Submitter: Nathan Myers Date: 6 Aug 1998
locale::name() is described as returning a string that can be passed to a locale constructor, but there is no matching constructor.
Proposed resolution:
In 22.1.1.3 [lib.locale.members], paragraph 5, replace "locale(name())" with "locale(name().c_str())".
Section: 22.2.1.4 [lib.locale.ctype.byname.special] Status: DR Submitter: Nathan Myers Date: 6 Aug 1998
The new virtual members ctype_byname<char>::do_widen and do_narrow did not get edited in properly. Instead, the member do_widen appears four times, with wrong argument lists.
Proposed resolution:
The correct declarations for the overloaded members do_narrow and do_widen should be copied from 22.2.1.3 [lib.facet.ctype.special].
Section: 22.2.2.1.2 [lib.facet.num.get.virtuals] Status: DR Submitter: Nathan Myers Date: 6 Aug 1998
This section describes the process of parsing a text boolean value from the input
stream. It does not say it recognizes either of the sequences "true" or
"false" and returns the corresponding bool value; instead, it says it recognizes
only one of those sequences, and chooses which according to the received value of a
reference argument intended for returning the result, and reports an error if the other
sequence is found. (!) Furthermore, it claims to get the names from the ctype<>
facet rather than the numpunct<> facet, and it examines the "boolalpha"
flag wrongly; it doesn't define the value "loc"; and finally, it computes
wrongly whether to use numeric or "alpha" parsing.
I believe the correct algorithm is "as if":
// in, err, val, and str are arguments.
err = 0;
const numpunct<charT>& np = use_facet<numpunct<charT> >(str.getloc());
const string_type t = np.truename(), f = np.falsename();
bool tm = true, fm = true;
size_t pos = 0;
while (tm && pos < t.size() || fm && pos < f.size()) {
if (in == end) { err = str.eofbit; }
bool matched = false;
if (tm && pos < t.size()) {
if (!err && t[pos] == *in) matched = true;
else tm = false;
}
if (fm && pos < f.size()) {
if (!err && f[pos] == *in) matched = true;
else fm = false;
}
if (matched) { ++in; ++pos; }
if (pos > t.size()) tm = false;
if (pos > f.size()) fm = false;
}
if (tm == fm || pos == 0) { err |= str.failbit; }
else { val = tm; }
return in;
Notice this works reasonably when the candidate strings are both empty, or equal, or when one is a substring of the other. The proposed text below captures the logic of the code above.
Proposed resolution:
In 22.2.2.1.2 [lib.facet.num.get.virtuals], in the first line of paragraph 14, change "&&" to "&".
Then, replace paragraphs 15 and 16 as follows:
Otherwise target sequences are determined "as if" by calling the members falsename() and truename() of the facet obtained by use_facet<numpunct<charT> >(str.getloc()). Successive characters in the range [in,end) (see [lib.sequence.reqmts]) are obtained and matched against corresponding positions in the target sequences only as necessary to identify a unique match. The input iterator in is compared to end only when necessary to obtain a character. If and only if a target sequence is uniquely matched, val is set to the corresponding value.
The in iterator is always left pointing one position beyond the last character successfully matched. If val is set, then err is set to str.goodbit; or to str.eofbit if, when seeking another character to match, it is found that (in==end). If val is not set, then err is set to str.failbit; or to (str.failbit|str.eofbit)if the reason for the failure was that (in==end). [Example: for targets true:"a" and false:"abb", the input sequence "a" yields val==true and err==str.eofbit; the input sequence "abc" yields err=str.failbit, with in ending at the 'c' element. For targets true:"1" and false:"0", the input sequence "1" yields val==true and err=str.goodbit. For empty targets (""), any input sequence yields err==str.failbit. --end example]
Section: 22.2.2.1.1 [lib.facet.num.get.members] Status: DR Submitter: Nathan Myers Date: 6 Aug 1998
In the list of num_get<> non-virtual members on page 22-23, the member that parses bool values was omitted from the list of definitions of non-virtual members, though it is listed in the class definition and the corresponding virtual is listed everywhere appropriate.
Proposed resolution:
Add at the beginning of 22.2.2.1.1 [lib.facet.num.get.members] another get member for bool&, copied from the entry in 22.2.2.1 [lib.locale.num.get].
Section: 22.2.1.5.2 [lib.locale.codecvt.virtuals] Status: DR Submitter: Nathan Myers Date: 6 Aug 1998
In the definitions of codecvt<>::do_out and do_in, they are specified to return noconv if "no conversion is needed". This definition is too vague, and does not say normatively what is done with the buffers.
Proposed resolution:
Change the entry for noconv in the table under paragraph 4 in section 22.2.1.5.2 [lib.locale.codecvt.virtuals] to read:
noconv: internT and externT are the same type, and input sequence is identical to converted sequence.
Change the Note in paragraph 2 to normative text as follows:
If returns noconv, internT and externT are the same type and the converted sequence is identical to the input sequence [from,from_next). to_next is set equal to to, the value of state is unchanged, and there are no changes to the values in [to, to_limit).
Section: 22.2.3.1.2 [lib.facet.numpunct.virtuals] Status: DR Submitter: Nathan Myers Date: 6 Aug 1998
The synopsis for numpunct<>::do_thousands_sep, and the definition of numpunct<>::thousands_sep which calls it, specify that it returns a value of type char_type. Here it is erroneously described as returning a "string_type".
Proposed resolution:
In 22.2.3.1.2 [lib.facet.numpunct.virtuals], above paragraph 2, change "string_type" to "char_type".
Section: 22.1.1.1.1 [lib.locale.category] Status: DR Submitter: Nathan Myers Date: 6 Aug 1998
In the second table in the section, captioned "Required instantiations", the instantiations for codecvt_byname<> have been omitted. These are necessary to allow users to construct a locale by name from facets.
Proposed resolution:
Add in 22.1.1.1.1 [lib.locale.category] to the table captioned "Required instantiations", in the category "ctype" the lines
codecvt_byname<char,char,mbstate_t>, codecvt_byname<wchar_t,char,mbstate_t>
Section: 27.8.1.7 [lib.ifstream.members] Status: DR Submitter: Nathan Myers Date: 6 Aug 1998
The description of basic_istream<>::open leaves unanswered questions about how it responds to or changes flags in the error status for the stream. A strict reading indicates that it ignores the bits and does not change them, which confuses users who do not expect eofbit and failbit to remain set after a successful open. There are three reasonable resolutions: 1) status quo 2) fail if fail(), ignore eofbit 3) clear failbit and eofbit on call to open().
Proposed resolution:
In 27.8.1.7 [lib.ifstream.members] paragraph 3, and in 27.8.1.10 [lib.ofstream.members] paragraph 3, under open() effects, add a footnote:
A successful open does not change the error state.
Section: 22.2.1.5.2 [lib.locale.codecvt.virtuals] Status: DR Submitter: Nathan Myers Date: 6 Aug 1998
The description of codecvt<>::do_out and do_in mentions a symbol "do_convert" which is not defined in the standard. This is a leftover from an edit, and should be "do_in and do_out".
Proposed resolution:
In 22.2.1.5 [lib.locale.codecvt], paragraph 3, change "do_convert" to "do_in or do_out". Also, in 22.2.1.5.2 [lib.locale.codecvt.virtuals], change "do_convert()" to "do_in or do_out".
Section: 21.3.7.9 [lib.string.io] Status: DR Submitter: Nathan Myers Date: 6 Aug 1998
In the description of operator<< applied to strings, the standard says that uses the smaller of os.width() and str.size(), to pad "as described in stage 3" elsewhere; but this is inconsistent, as this allows no possibility of space for padding.
Proposed resolution:
Change 21.3.7.9 [lib.string.io] paragraph 4 from:
"... where n is the smaller of os.width() and str.size();
..."
to:
"... where n is the larger of os.width() and str.size();
..."
Section: 27.6.1.1.2 [lib.istream::sentry] Status: DR Submitter: Nathan Myers Date: 6 Aug 1998
In paragraph 6, the code in the example:
template <class charT, class traits = char_traits<charT> >
basic_istream<charT,traits>::sentry(
basic_istream<charT,traits>& is, bool noskipws = false) {
...
int_type c;
typedef ctype<charT> ctype_type;
const ctype_type& ctype = use_facet<ctype_type>(is.getloc());
while ((c = is.rdbuf()->snextc()) != traits::eof()) {
if (ctype.is(ctype.space,c)==0) {
is.rdbuf()->sputbackc (c);
break;
}
}
...
}
fails to demonstrate correct use of the facilities described. In particular, it fails to use traits operators, and specifies incorrect semantics. (E.g. it specifies skipping over the first character in the sequence without examining it.)
Proposed resolution:
Remove the example above from 27.6.1.1.2 [lib.istream::sentry] paragraph 6.
Rationale:
The originally proposed replacement code for the example was not correct. The LWG tried in Kona and again in Tokyo to correct it without success. In Tokyo, an implementor reported that actual working code ran over one page in length and was quite complicated. The LWG decided that it would be counter-productive to include such a lengthy example, which might well still contain errors.
Section: 21.3.5.5 [lib.string::erase] Status: DR Submitter: Nathan Myers Date: 6 Aug 1998
The string::erase(iterator first, iterator last) is specified to return an element one place beyond the next element after the last one erased. E.g. for the string "abcde", erasing the range ['b'..'d') would yield an iterator for element 'e', while 'd' has not been erased.
Proposed resolution:
In 21.3.5.5 [lib.string::erase], paragraph 10, change:
Returns: an iterator which points to the element immediately following _last_ prior to the element being erased.
to read
Returns: an iterator which points to the element pointed to by _last_ prior to the other elements being erased.
Section: 22.2.1.3.2 [lib.facet.ctype.char.members] Status: DR Submitter: Nathan Myers Date: 6 Aug 1998
The description of the vector form of ctype<char>::is can be interpreted to mean something very different from what was intended. Paragraph 4 says
Effects: The second form, for all *p in the range [low, high), assigns vec[p-low] to table()[(unsigned char)*p].
This is intended to copy the value indexed from table()[] into the place identified in vec[].
Proposed resolution:
Change 22.2.1.3.2 [lib.facet.ctype.char.members], paragraph 4, to read
Effects: The second form, for all *p in the range [low, high), assigns into vec[p-low] the value table()[(unsigned char)*p].
Section: 27.3.1 [lib.narrow.stream.objects] Status: DR Submitter: Nathan Myers Date: 6 Aug 1998
Sections 27.3.1 [lib.narrow.stream.objects] and 27.3.2 [lib.wide.stream.objects] mention a function ios_base::init, which is not defined. Probably they mean basic_ios<>::init, defined in 27.4.4.1 [lib.basic.ios.cons], paragraph 3.
Proposed resolution:
[R12: modified to include paragraph 5.]
In 27.3.1 [lib.narrow.stream.objects] paragraph 2 and 5, change
ios_base::init
to
basic_ios<char>::init
Also, make a similar change in 27.3.2 [lib.wide.stream.objects] except it should read
basic_ios<wchar_t>::init
Section: 22.1.1.1.1 [lib.locale.category] Status: DR Submitter: Nathan Myers Date: 6 Aug 1998
Paragraph 2 implies that the C macros LC_CTYPE etc. are defined in <cctype>, where they are in fact defined elsewhere to appear in <clocale>.
Proposed resolution:
In 22.1.1.1.1 [lib.locale.category], paragraph 2, change "<cctype>" to read "<clocale>".
Section: 22.1.1 [lib.locale] Status: DR Submitter: Nathan Myers Date: 6 Aug 1998
Paragraph 6, says "An instance of locale is immutable; once a facet reference is obtained from it, ...". This has caused some confusion, because locale variables are manifestly assignable.
Proposed resolution:
In 22.1.1 [lib.locale] replace paragraph 6
An instance of locale is immutable; once a facet reference is obtained from it, that reference remains usable as long as the locale value itself exists.
with
Once a facet reference is obtained from a locale object by calling use_facet<>, that reference remains usable, and the results from member functions of it may be cached and re-used, as long as some locale object refers to that facet.
Section: 27.5.2.4.4 [lib.streambuf.virt.pback] Status: DR Submitter: Nathan Myers Date: 6 Aug 1998
The description of the required state before calling virtual member basic_streambuf<>::pbackfail requirements is inconsistent with the conditions described in 27.5.2.2.4 [lib.streambuf.pub.pback] where member sputbackc calls it. Specifically, the latter says it calls pbackfail if:
traits::eq(c,gptr()[-1]) is false
where pbackfail claims to require:
traits::eq(*gptr(),traits::to_char_type(c)) returns false
It appears that the pbackfail description is wrong.
Proposed resolution:
In 27.5.2.4.4 [lib.streambuf.virt.pback], paragraph 1, change:
"traits::eq(*gptr(),traits::to_char_type( c))"
to
"traits::eq(traits::to_char_type(c),gptr()[-1])"
Rationale:
Note deliberate reordering of arguments for clarity in addition to the correction of the argument value.
Section: 22.2.1.5.2 [lib.locale.codecvt.virtuals] Status: DR Submitter: Nathan Myers Date: 6 Aug 1998
In the table defining the results from do_out and do_in, the specification for the result error says
encountered a from_type character it could not convert
but from_type is not defined. This clearly is intended to be an externT for do_in, or an internT for do_out.
Proposed resolution:
In 22.2.1.5.2 [lib.locale.codecvt.virtuals] paragraph 4, replace the definition in the table for the case of _error_ with
encountered a character in [from,from_end) that it could not convert.
Section: 22.2.2.2.2 [lib.facet.num.put.virtuals] Status: DR Submitter: Nathan Myers Date: 6 Aug 1998
In paragraph 19, Effects:, members truename() and falsename are used from facet ctype<charT>, but it has no such members. Note that this is also a problem in 22.2.2.1.2, addressed in (4).
Proposed resolution:
In 22.2.2.2.2 [lib.facet.num.put.virtuals], paragraph 19, in the Effects: clause for member put(...., bool), replace the initialization of the string_type value s as follows:
const numpunct& np = use_facet<numpunct<charT> >(loc); string_type s = val ? np.truename() : np.falsename();
Section: 27.4 [lib.iostreams.base] Status: DR Submitter: Nathan Myers Date: 6 Aug 1998
In 27.4.5.1 [lib.fmtflags.manip], we have a definition for a manipulator named "unitbuf". Unlike other manipulators, it's not listed in synopsis. Similarly for "nounitbuf".
Proposed resolution:
Add to the synopsis for <ios> in 27.4 [lib.iostreams.base], after the entry for "nouppercase", the prototypes:
ios_base& unitbuf(ios_base& str); ios_base& nounitbuf(ios_base& str);
Section: 27.4.2.5 [lib.ios.base.storage] Status: DR Submitter: Nathan Myers Date: 6 Aug 1998
In the definitions for ios_base::iword and pword, the lifetime of the storage is specified badly, so that an implementation which only keeps the last value stored appears to conform. In particular, it says:
The reference returned may become invalid after another call to the object's iword member with a different index ...
This is not idle speculation; at least one implementation was done this way.
Proposed resolution:
Add in 27.4.2.5 [lib.ios.base.storage], in both paragraph 2 and also in paragraph 4, replace the sentence:
The reference returned may become invalid after another call to the object's iword [pword] member with a different index, after a call to its copyfmt member, or when the object is destroyed.
with:
The reference returned is invalid after any other operations on the object. However, the value of the storage referred to is retained, so that until the next call to copyfmt, calling iword [pword] with the same index yields another reference to the same value.
substituting "iword" or "pword" as appropriate.
Section: 22.1.1 [lib.locale] Status: DR Submitter: Nathan Myers Date: 6 Aug 1998
In the overview of locale semantics, paragraph 4, is the sentence
If Facet is not present in a locale (or, failing that, in the global locale), it throws the standard exception bad_cast.
This is not supported by the definition of use_facet<>, and represents semantics from an old draft.
Proposed resolution:
In 22.1.1 [lib.locale], paragraph 4, delete the parenthesized expression
(or, failing that, in the global locale)
Section: 22.1.2 [lib.locale.global.templates] Status: DR Submitter: Nathan Myers Date: 6 Aug 1998
It has been noticed by Esa Pulkkinen that the definition of "facet" is incomplete. In particular, a class derived from another facet, but which does not define a member id, cannot safely serve as the argument F to use_facet<F>(loc), because there is no guarantee that a reference to the facet instance stored in loc is safely convertible to F.
Proposed resolution:
In the definition of std::use_facet<>(), replace the text in paragraph 1 which reads:
Get a reference to a facet of a locale.
with:
Requires: Facet is a facet class whose definition contains the public static member id as defined in 22.1.1.1.2 [lib.locale.facet].
[ Kona: strike as overspecification the text "(not inherits)" from the original resolution, which read "... whose definition contains (not inherits) the public static member id..." ]
Section: 24.5.3.4 [lib.istreambuf.iterator::op++] Status: DR Submitter: Nathan Myers Date: 6 Aug 1998
Following the definition of istreambuf_iterator<>::operator++(int) in paragraph 3, the standard contains three lines of garbage text left over from a previous edit.
istreambuf_iterator<charT,traits> tmp = *this; sbuf_->sbumpc(); return(tmp);
Proposed resolution:
In 24.5.3.4 [lib.istreambuf.iterator::op++], delete the three lines of code at the end of paragraph 3.
Section: 22.2.8 [lib.facets.examples] Status: DR Submitter: Nathan Myers Date: 6 Aug 1998
Paragraph 3 of the locale examples is a description of part of an implementation technique that has lost its referent, and doesn't mean anything.
Proposed resolution:
Delete 22.2.8 [lib.facets.examples] paragraph 3 which begins "This initialization/identification system depends...", or (at the editor's option) replace it with a place-holder to keep the paragraph numbering the same.
Section: 27.4.2 [lib.ios.base] Status: DR Submitter: Nathan Myers Date: 6 Aug 1998
The description of ios_base::iword() and pword() in 27.4.2.4 [lib.ios.members.static], say that if they fail, they "set badbit, which may throw an exception". However, ios_base offers no interface to set or to test badbit; those interfaces are defined in basic_ios<>.
Proposed resolution:
Change the description in 27.4.2.5 [lib.ios.base.storage] in paragraph 2, and also in paragraph 4, as follows. Replace
If the function fails it sets badbit, which may throw an exception.
with
If the function fails, and *this is a base sub-object of a basic_ios<> object or sub-object, the effect is equivalent to calling basic_ios<>::setstate(badbit) on the derived object (which may throw failure).
[Kona: LWG reviewed wording; setstate(failbit) changed to setstate(badbit).]
Section: 21.3 [lib.basic.string] Status: DR Submitter: Nathan Myers Date: 6 Aug 1998
The basic_string<> copy constructor:
basic_string(const basic_string& str, size_type pos = 0,
size_type n = npos, const Allocator& a = Allocator());
specifies an Allocator argument default value that is counter-intuitive. The natural choice for a the allocator to copy from is str.get_allocator(). Though this cannot be expressed in default-argument notation, overloading suffices.
Alternatively, the other containers in Clause 23 (deque, list, vector) do not have this form of constructor, so it is inconsistent, and an evident source of confusion, for basic_string<> to have it, so it might better be removed.
Proposed resolution:
In 21.3 [lib.basic.string], replace the declaration of the copy constructor as follows:
basic_string(const basic_string& str);
basic_string(const basic_string& str, size_type pos, size_type n = npos,
const Allocator& a = Allocator());
In 21.3.1 [lib.string.cons], replace the copy constructor declaration as above. Add to paragraph 5, Effects:
In the first form, the Allocator value used is copied from str.get_allocator().
Rationale:
The LWG believes the constructor is actually broken, rather than just an unfortunate design choice.
The LWG considered two other possible resolutions:
A. In 21.3 [lib.basic.string], replace the declaration of the copy constructor as follows:
basic_string(const basic_string& str, size_type pos = 0,
size_type n = npos);
basic_string(const basic_string& str, size_type pos,
size_type n, const Allocator& a);
In 21.3.1 [lib.string.cons], replace the copy constructor declaration as above. Add to paragraph 5, Effects:
When no Allocator argument is provided, the string is constructed using the value str.get_allocator().
B. In 21.3 [lib.basic.string], and also in 21.3.1 [lib.string.cons], replace the declaration of the copy constructor as follows:
basic_string(const basic_string& str, size_type pos = 0,
size_type n = npos);
The proposed resolution reflects the original intent of the LWG. It was also noted by Pete Becker that this fix "will cause a small amount of existing code to now work correctly."
[ Kona: issue editing snafu fixed - the proposed resolution now correctly reflects the LWG consensus. ]
Section: D.7 [depr.str.strstreams] Status: DR Submitter: Brendan Kehoe Date: 1 Jun 1998
See lib-6522 and edit-814.
Proposed resolution:
Change D.7.1 [depr.strstreambuf] (since streambuf is a typedef of basic_streambuf<char>) from:
virtual streambuf<char>* setbuf(char* s, streamsize n);
to:
virtual streambuf* setbuf(char* s, streamsize n);
In D.7.4 [depr.strstream] insert the semicolon now missing after int_type:
namespace std {
class strstream
: public basic_iostream<char> {
public:
// Types
typedef char char_type;
typedef typename char_traits<char>::int_type int_type
typedef typename char_traits<char>::pos_type pos_type;
Section: 27.4.2.3 [lib.ios.base.locales] Status: DR Submitter: Matt Austern Date: 21 Jun 1998
Section 27.4.2.3 specifies how imbue() and getloc() work. That section has two RETURNS clauses, and they make no sense as stated. They make perfect sense, though, if you swap them. Am I correct in thinking that paragraphs 2 and 4 just got mixed up by accident?
Proposed resolution:
In 27.4.2.3 [lib.ios.base.locales] swap paragraphs 2 and 4.
Section: 27.4.2.1.1 [lib.ios::failure] Status: DR Submitter: Matt Austern Date: 21 Jun 1998
27.4.2.1.1, paragraph 2, says that class failure initializes the base class, exception, with exception(msg). Class exception (see 18.6.1) has no such constructor.
Proposed resolution:
Replace 27.4.2.1.1 [lib.ios::failure], paragraph 2, with
EFFECTS: Constructs an object of class failure.
Section: 27.4.2 [lib.ios.base] Status: DR Submitter: Matt Austern Date: 21 Jun 1998
As written, ios_base has a copy constructor and an assignment operator. (Nothing in the standard says it doesn't have one, and all classes have copy constructors and assignment operators unless you take specific steps to avoid them.) However, nothing in 27.4.2 says what the copy constructor and assignment operator do.
My guess is that this was an oversight, that ios_base is, like basic_ios, not supposed to have a copy constructor or an assignment operator.
Jerry Schwarz comments: Yes, its an oversight, but in the opposite sense to what you're suggesting. At one point there was a definite intention that you could copy ios_base. It's an easy way to save the entire state of a stream for future use. As you note, to carry out that intention would have required a explicit description of the semantics (e.g. what happens to the iarray and parray stuff).
Proposed resolution:
In 27.4.2 [lib.ios.base], class ios_base, specify the copy constructor and operator= members as being private.
Rationale:
The LWG believes the difficulty of specifying correct semantics outweighs any benefit of allowing ios_base objects to be copyable.
Section: 23.1 [lib.container.requirements] Status: DR Submitter: David Vandevoorde Date: 23 Jun 1998
The std::sort algorithm can in general only sort a given sequence by moving around values. The list<>::sort() member on the other hand could move around values or just update internal pointers. Either method can leave iterators into the list<> dereferencable, but they would point to different things.
Does the FDIS mandate anywhere which method should be used for list<>::sort()?
Matt Austern comments:
I think you've found an omission in the standard.
The library working group discussed this point, and there was supposed to be a general requirement saying that list, set, map, multiset, and multimap may not invalidate iterators, or change the values that iterators point to, except when an operation does it explicitly. So, for example, insert() doesn't invalidate any iterators and erase() and remove() only invalidate iterators pointing to the elements that are being erased.
I looked for that general requirement in the FDIS, and, while I found a limited form of it for the sorted associative containers, I didn't find it for list. It looks like it just got omitted.
The intention, though, is that list<>::sort does not invalidate any iterators and does not change the values that any iterator points to. There would be no reason to have the member function otherwise.
Proposed resolution:
Add a new paragraph at the end of 23.1:
Unless otherwise specified (either explicitly or by defining a function in terms of other functions), invoking a container member function or passing a container as an argument to a library function shall not invalidate iterators to, or change the values of, objects within that container.
Rationale:
This was US issue CD2-23-011; it was accepted in London but the change was not made due to an editing oversight. The wording in the proposed resolution below is somewhat updated from CD2-23-011, particularly the addition of the phrase "or change the values of"
Section: 27.4.3.2 [lib.fpos.operations] Status: DR Submitter: Matt Austern Date: 23 Jun 1998
First, 27.4.4.1 [lib.basic.ios.cons], table 89. This is pretty obvious: it should be titled "basic_ios<>() effects", not "ios_base() effects".
[The second item is a duplicate; see issue 6 for resolution.]
Second, 27.4.3.2 [lib.fpos.operations] table 88 . There are a couple different things wrong with it, some of which I've already discussed with Jerry, but the most obvious mechanical sort of error is that it uses expressions like P(i) and p(i), without ever defining what sort of thing "i" is.
(The other problem is that it requires support for streampos arithmetic. This is impossible on some systems, i.e. ones where file position is a complicated structure rather than just a number. Jerry tells me that the intention was to require syntactic support for streampos arithmetic, but that it wasn't actually supposed to do anything meaningful except on platforms, like Unix, where genuine arithmetic is possible.)
Proposed resolution:
Change 27.4.4.1 [lib.basic.ios.cons] table 89 title from "ios_base() effects" to "basic_ios<>() effects".
Section: 27.4.4.1 [lib.basic.ios.cons] Status: DR Submitter: Matt Austern Date: 23 Jun 1998
There's nothing in 27.4.4 saying what basic_ios's destructor does. The important question is whether basic_ios::~basic_ios() destroys rdbuf().
Proposed resolution:
Add after 27.4.4.1 [lib.basic.ios.cons] paragraph 2:
virtual ~basic_ios();
Notes: The destructor does not destroy rdbuf().
Rationale:
The LWG reviewed the additional question of whether or not rdbuf(0) may set badbit. The answer is clearly yes; it may be set via clear(). See 27.4.4.2 [lib.basic.ios.members], paragraph 6. This issue was reviewed at length by the LWG, which removed from the original proposed resolution a footnote which incorrectly said "rdbuf(0) does not set badbit".
Section: 27.5.2.1 [lib.streambuf.cons] Status: DR Submitter: Matt Austern Date: 25 Jun 1998
The class synopsis for basic_streambuf shows a (virtual) destructor, but the standard doesn't say what that destructor does. My assumption is that it does nothing, but the standard should say so explicitly.
Proposed resolution:
Add after 27.5.2.1 [lib.streambuf.cons] paragraph 2:
virtual ~basic_streambuf();
Effects: None.
Section: 27 [lib.input.output] Status: DR Submitter: Matt Austern Date: 26 Jun 1998
Several member functions in clause 27 are defined in certain circumstances to return an "invalid stream position", a term that is defined nowhere in the standard. Two places (27.5.2.4.2, paragraph 4, and 27.8.1.4, paragraph 15) contain a cross-reference to a definition in _lib.iostreams.definitions_, a nonexistent section.
I suspect that the invalid stream position is just supposed to be pos_type(-1). Probably best to say explicitly in (for example) 27.5.2.4.2 that the return value is pos_type(-1), rather than to use the term "invalid stream position", define that term somewhere, and then put in a cross-reference.
The phrase "invalid stream position" appears ten times in the C++ Standard. In seven places it refers to a return value, and it should be changed. In three places it refers to an argument, and it should not be changed. Here are the three places where "invalid stream position" should not be changed:
27.7.1.3 [lib.stringbuf.virtuals], paragraph 14
27.8.1.4 [lib.filebuf.virtuals], paragraph 14
D.7.1.3 [depr.strstreambuf.virtuals], paragraph 17
Proposed resolution:
In 27.5.2.4.2 [lib.streambuf.virt.buffer], paragraph 4, change "Returns an object of class pos_type that stores an invalid stream position (_lib.iostreams.definitions_)" to "Returns pos_type(off_type(-1))".
In 27.5.2.4.2 [lib.streambuf.virt.buffer], paragraph 6, change "Returns an object of class pos_type that stores an invalid stream position" to "Returns pos_type(off_type(-1))".
In 27.7.1.3 [lib.stringbuf.virtuals], paragraph 13, change "the object stores an invalid stream position" to "the return value is pos_type(off_type(-1))".
In 27.8.1.4 [lib.filebuf.virtuals], paragraph 13, change "returns an invalid stream position (27.4.3)" to "returns pos_type(off_type(-1))"
In 27.8.1.4 [lib.filebuf.virtuals], paragraph 15, change "Otherwise returns an invalid stream position (_lib.iostreams.definitions_)" to "Otherwise returns pos_type(off_type(-1))"
In D.7.1.3 [depr.strstreambuf.virtuals], paragraph 15, change "the object stores an invalid stream position" to "the return value is pos_type(off_type(-1))"
In D.7.1.3 [depr.strstreambuf.virtuals], paragraph 18, change "the object stores an invalid stream position" to "the return value is pos_type(off_type(-1))"
Section: 27.5.2 [lib.streambuf] Status: DR Submitter: Matt Austern Date: 29 Jun 1998
The class summary for basic_streambuf<>, in 27.5.2, says that showmanyc has return type int. However, 27.5.2.4.3 says that its return type is streamsize.
Proposed resolution:
Change showmanyc's return type in the 27.5.2 [lib.streambuf] class summary to streamsize.
Section: 21.1.3.2 [lib.char.traits.specializations.wchar.t] Status: DR Submitter: Matt Austern Date: 1 Jul 1998
21.1.3.2, paragraph 3, says "The types streampos and wstreampos may be different if the implementation supports no shift encoding in narrow-oriented iostreams but supports one or more shift encodings in wide-oriented streams".
That's wrong: the two are the same type. The <iosfwd> summary in 27.2 says that streampos and wstreampos are, respectively, synonyms for fpos<char_traits<char>::state_type> and fpos<char_traits<wchar_t>::state_type>, and, flipping back to clause 21, we see in 21.1.3.1 and 21.1.3.2 that char_traits<char>::state_type and char_traits<wchar_t>::state_type must both be mbstate_t.
Proposed resolution:
Remove the sentence in 21.1.3.2 [lib.char.traits.specializations.wchar.t] paragraph 3 which begins "The types streampos and wstreampos may be different..." .
Section: 27.5.2.3.1 [lib.streambuf.get.area] Status: DR Submitter: Matt Austern Date: 28 Jul 1998
27.5.2.3.1 says that basic_streambuf::gbump() "Advances the next pointer for the input sequence by n."
The straightforward interpretation is that it is just gptr() += n. An alternative interpretation, though, is that it behaves as if it calls sbumpc n times. (The issue, of course, is whether it might ever call underflow.) There is a similar ambiguity in the case of pbump.
(The "classic" AT&T implementation used the former interpretation.)
Proposed resolution:
Change 27.5.2.3.1 [lib.streambuf.get.area] paragraph 4 gbump effects from:
Effects: Advances the next pointer for the input sequence by n.
to:
Effects: Adds n to the next pointer for the input sequence.
Make the same change to 27.5.2.3.2 [lib.streambuf.put.area] paragraph 4 pbump effects.
Section: 27.6.1.2.1 [lib.istream.formatted.reqmts] Status: DR Submitter: Matt Austern Date: 3 Aug 1998
Paragraph 1 of 27.6.1.2.1 contains general requirements for all formatted input functions. Some of the functions defined in section 27.6.1.2 explicitly say that those requirements apply ("Behaves like a formatted input member (as described in 27.6.1.2.1)"), but others don't. The question: is 27.6.1.2.1 supposed to apply to everything in 27.6.1.2, or only to those member functions that explicitly say "behaves like a formatted input member"? Or to put it differently: are we to assume that everything that appears in a section called "Formatted input functions" really is a formatted input function? I assume that 27.6.1.2.1 is intended to apply to the arithmetic extractors (27.6.1.2.2), but I assume that it is not intended to apply to extractors like
basic_istream& operator>>(basic_istream& (*pf)(basic_istream&));
and
basic_istream& operator>>(basic_streammbuf*);
There is a similar ambiguity for unformatted input, formatted output, and unformatted output.
Comments from Judy Ward: It seems like the problem is that the basic_istream and basic_ostream operator <<()'s that are used for the manipulators and streambuf* are in the wrong section and should have their own separate section or be modified to make it clear that the "Common requirements" listed in section 27.6.1.2.1 (for basic_istream) and section 27.6.2.5.1 (for basic_ostream) do not apply to them.
Additional comments from Dietmar Kühl: It appears to be somewhat nonsensical to consider the functions defined in 27.6.1.2.3 [lib.istream::extractors] paragraphs 1 to 5 to be "Formatted input function" but since these functions are defined in a section labeled "Formatted input functions" it is unclear to me whether these operators are considered formatted input functions which have to conform to the "common requirements" from 27.6.1.2.1 [lib.istream.formatted.reqmts]: If this is the case, all manipulators, not just ws, would skip whitespace unless noskipws is set (... but setting noskipws using the manipulator syntax would also skip whitespace :-)
It is not clear which functions are to be considered unformatted input functions. As written, it seems that all functions in 27.6.1.3 [lib.istream.unformatted] are unformatted input functions. However, it does not really make much sense to construct a sentry object for gcount(), sync(), ... Also it is unclear what happens to the gcount() if eg. gcount(), putback(), unget(), or sync() is called: These functions don't extract characters, some of them even "unextract" a character. Should this still be reflected in gcount()? Of course, it could be read as if after a call to gcount() gcount() return 0 (the last unformatted input function, gcount(), didn't extract any character) and after a call to putback() gcount() returns -1 (the last unformatted input function putback() did "extract" back into the stream). Correspondingly for unget(). Is this what is intended? If so, this should be clarified. Otherwise, a corresponding clarification should be used.
Proposed resolution:
In 27.6.1.2.2 [lib.istream.formatted.arithmetic], paragraph 1. Change the beginning of the second sentence from "The conversion occurs" to "These extractors behave as formatted input functions (as described in 27.6.1.2.1). After a sentry object is constructed, the conversion occurs"
In 27.6.1.2.3, [lib.istream::extractors], before paragraph 1. Add an effects clause. "Effects: None. This extractor does not behave as a formatted input function (as described in 27.6.1.2.1).
In 27.6.1.2.3, [lib.istream::extractors], paragraph 2. Change the effects clause to "Effects: Calls pf(*this). This extractor does not behave as a formatted input function (as described in 27.6.1.2.1).
In 27.6.1.2.3, [lib.istream::extractors], paragraph 4. Change the effects clause to "Effects: Calls pf(*this). This extractor does not behave as a formatted input function (as described in 27.6.1.2.1).
In 27.6.1.2.3, [lib.istream::extractors], paragraph 12. Change the first two sentences from "If sb is null, calls setstate(failbit), which may throw ios_base::failure (27.4.4.3). Extracts characters from *this..." to "Behaves as a formatted input function (as described in 27.6.1.2.1). If sb is null, calls setstate(failbit), which may throw ios_base::failure (27.4.4.3). After a sentry object is constructed, extracts characters from *this...".
In 27.6.1.3, [lib.istream.unformatted], before paragraph 2. Add an effects clause. "Effects: none. This member function does not behave as an unformatted input function (as described in 27.6.1.3, paragraph 1)."
In 27.6.1.3, [lib.istream.unformatted], paragraph 3. Change the beginning of the first sentence of the effects clause from "Extracts a character" to "Behaves as an unformatted input function (as described in 27.6.1.3, paragraph 1). After constructing a sentry object, extracts a character"
In 27.6.1.3, [lib.istream.unformatted], paragraph 5. Change the beginning of the first sentence of the effects clause from "Extracts a character" to "Behaves as an unformatted input function (as described in 27.6.1.3, paragraph 1). After constructing a sentry object, extracts a character"
In 27.6.1.3, [lib.istream.unformatted], paragraph 5. Change the beginning of the first sentence of the effects clause from "Extracts characters" to "Behaves as an unformatted input function (as described in 27.6.1.3, paragraph 1). After constructing a sentry object, extracts characters"
[No change needed in paragraph 10, because it refers to paragraph 7.]
In 27.6.1.3, [lib.istream.unformatted], paragraph 12. Change the beginning of the first sentence of the effects clause from "Extracts characters" to "Behaves as an unformatted input function (as described in 27.6.1.3, paragraph 1). After constructing a sentry object, extracts characters"
[No change needed in paragraph 15.]
In 27.6.1.3, [lib.istream.unformatted], paragraph 17. Change the beginning of the first sentence of the effects clause from "Extracts characters" to "Behaves as an unformatted input function (as described in 27.6.1.3, paragraph 1). After constructing a sentry object, extracts characters"
[No change needed in paragraph 23.]
In 27.6.1.3, [lib.istream.unformatted], paragraph 24. Change the beginning of the first sentence of the effects clause from "Extracts characters" to "Behaves as an unformatted input function (as described in 27.6.1.3, paragraph 1). After constructing a sentry object, extracts characters"
In 27.6.1.3, [lib.istream.unformatted], before paragraph 27. Add an Effects clause: "Effects: Behaves as an unformatted input function (as described in 27.6.1.3, paragraph 1). After constructing a sentry object, reads but does not extract the current input character."
In 27.6.1.3, [lib.istream.unformatted], paragraph 28. Change the first sentence of the Effects clause from "If !good() calls" to Behaves as an unformatted input function (as described in 27.6.1.3, paragraph 1). After constructing a sentry object, if !good() calls"
In 27.6.1.3, [lib.istream.unformatted], paragraph 30. Change the first sentence of the Effects clause from "If !good() calls" to "Behaves as an unformatted input function (as described in 27.6.1.3, paragraph 1). After constructing a sentry object, if !good() calls"
In 27.6.1.3, [lib.istream.unformatted], paragraph 32. Change the first sentence of the Effects clause from "If !good() calls..." to "Behaves as an unformatted input function (as described in 27.6.1.3, paragraph 1). After constructing a sentry object, if !good() calls..." Add a new sentence to the end of the Effects clause: "[Note: this function extracts no characters, so the value returned by the next call to gcount() is 0.]"
In 27.6.1.3, [lib.istream.unformatted], paragraph 34. Change the first sentence of the Effects clause from "If !good() calls" to "Behaves as an unformatted input function (as described in 27.6.1.3, paragraph 1). After constructing a sentry object, if !good() calls". Add a new sentence to the end of the Effects clause: "[Note: this function extracts no characters, so the value returned by the next call to gcount() is 0.]"
In 27.6.1.3, [lib.istream.unformatted], paragraph 36. Change the first sentence of the Effects clause from "If !rdbuf() is" to "Behaves as an unformatted input function (as described in 27.6.1.3, paragraph 1), except that it does not count the number of characters extracted and does not affect the value returned by subsequent calls to gcount(). After constructing a sentry object, if rdbuf() is"
In 27.6.1.3, [lib.istream.unformatted], before paragraph 37. Add an Effects clause: "Effects: Behaves as an unformatted input function (as described in 27.6.1.3, paragraph 1), except that it does not count the number of characters extracted and does not affect the value returned by subsequent calls to gcount()." Change the first sentence of paragraph 37 from "if fail()" to "after constructing a sentry object, if fail()".
In 27.6.1.3, [lib.istream.unformatted], paragraph 38. Change the first sentence of the Effects clause from "If fail()" to "Behaves as an unformatted input function (as described in 27.6.1.3, paragraph 1), except that it does not count the number of characters extracted and does not affect the value returned by subsequent calls to gcount(). After constructing a sentry object, if fail()
In 27.6.1.3, [lib.istream.unformatted], paragraph 40. Change the first sentence of the Effects clause from "If fail()" to "Behaves as an unformatted input function (as described in 27.6.1.3, paragraph 1), except that it does not count the number of characters extracted and does not affect the value returned by subsequent calls to gcount(). After constructing a sentry object, if fail()
In 27.6.2.5.2 [lib.ostream.inserters.arithmetic], paragraph 1. Change the beginning of the third sentence from "The formatting conversion" to "These extractors behave as formatted output functions (as described in 27.6.2.5.1). After the sentry object is constructed, the conversion occurs".
In 27.6.2.5.3 [lib.ostream.inserters], before paragraph 1. Add an effects clause: "Effects: None. Does not behave as a formatted output function (as described in 27.6.2.5.1).".
In 27.6.2.5.3 [lib.ostream.inserters], paragraph 2. Change the effects clause to "Effects: calls pf(*this). This extractor does not behave as a formatted output function (as described in 27.6.2.5.1).".
In 27.6.2.5.3 [lib.ostream.inserters], paragraph 4. Change the effects clause to "Effects: calls pf(*this). This extractor does not behave as a formatted output function (as described in 27.6.2.5.1).".
In 27.6.2.5.3 [lib.ostream.inserters], paragraph 6. Change the first sentence from "If sb" to "Behaves as a formatted output function (as described in 27.6.2.5.1). After the sentry object is constructed, if sb".
In 27.6.2.6 [lib.ostream.unformatted], paragraph 2. Change the first sentence from "Inserts the character" to "Behaves as an unformatted output function (as described in 27.6.2.6, paragraph 1). After constructing a sentry object, inserts the character".
In 27.6.2.6 [lib.ostream.unformatted], paragraph 5. Change the first sentence from "Obtains characters" to "Behaves as an unformatted output function (as described in 27.6.2.6, paragraph 1). After constructing a sentry object, obtains characters".
In 27.6.2.6 [lib.ostream.unformatted], paragraph 7. Add a new sentence at the end of the paragraph: "Does not behave as an unformatted output function (as described in 27.6.2.6, paragraph 1)."
Rationale:
See J16/99-0043==WG21/N1219, Proposed Resolution to Library Issue 60, by Judy Ward and Matt Austern. This proposed resolution is section VI of that paper.
Section: 27.6.1.3 [lib.istream.unformatted] Status: DR Submitter: Matt Austern Date: 6 Aug 1998
The introduction to the section on unformatted input (27.6.1.3) says that every unformatted input function catches all exceptions that were thrown during input, sets badbit, and then conditionally rethrows the exception. That seems clear enough. Several of the specific functions, however, such as get() and read(), are documented in some circumstances as setting eofbit and/or failbit. (The standard notes, correctly, that setting eofbit or failbit can sometimes result in an exception being thrown.) The question: if one of these functions throws an exception triggered by setting failbit, is this an exception "thrown during input" and hence covered by 27.6.1.3, or does 27.6.1.3 only refer to a limited class of exceptions? Just to make this concrete, suppose you have the following snippet.
char buffer[N]; istream is; ... is.exceptions(istream::failbit); // Throw on failbit but not on badbit. is.read(buffer, N);
Now suppose we reach EOF before we've read N characters. What iostate bits can we expect to be set, and what exception (if any) will be thrown?
Proposed resolution:
In 27.6.1.3, paragraph 1, after the sentence that begins "If an exception is thrown...", add the following parenthetical comment: "(Exceptions thrown from basic_ios<>::clear() are not caught or rethrown.)"
Rationale:
The LWG looked to two alternative wordings, and choose the proposed resolution as better standardese.
Section: 27.6.1.3 [lib.istream.unformatted] Status: DR Submitter: Matt Austern Date: 6 Aug 1998
The Effects clause for sync() (27.6.1.3, paragraph 36) says that it "calls rdbuf()->pubsync() and, if that function returns -1 ... returns traits::eof()."
That looks suspicious, because traits::eof() is of type traits::int_type while the return type of sync() is int.
Proposed resolution:
In 27.6.1.3 [lib.istream.unformatted], paragraph 36, change "returns traits::eof()" to "returns -1".
Section: 27.6.2.6 [lib.ostream.unformatted] Status: DR Submitter: Matt Austern Date: 11 Aug 1998
Clause 27 details an exception-handling policy for formatted input, unformatted input, and formatted output. It says nothing for unformatted output (27.6.2.6). 27.6.2.6 should either include the same kind of exception-handling policy as in the other three places, or else it should have a footnote saying that the omission is deliberate.
Proposed resolution:
In 27.6.2.6, paragraph 1, replace the last sentence ("In any case, the unformatted output function ends by destroying the sentry object, then returning the value specified for the formatted output function.") with the following text:
If an exception is thrown during output, then ios::badbit is turned on [Footnote: without causing an ios::failure to be thrown.] in *this's error state. If (exceptions() & badbit) != 0 then the exception is rethrown. In any case, the unformatted output function ends by destroying the sentry object, then, if no exception was thrown, returning the value specified for the formatted output function.
Rationale:
This exception-handling policy is consistent with that of formatted input, unformatted input, and formatted output.
Section: 27.6.1.2.3 [lib.istream::extractors] Status: DR Submitter: Matt Austern Date: 11 Aug 1998
27.6.1.2.3, paragraph 13, is ambiguous. It can be interpreted two different ways, depending on whether the second sentence is read as an elaboration of the first.
Proposed resolution:
Replace 27.6.1.2.3, paragraph 13, which begins "If the function inserts no characters ..." with:
If the function inserts no characters, it calls setstate(failbit), which may throw ios_base::failure (27.4.4.3). If it inserted no characters because it caught an exception thrown while extracting characters from sb and failbit is on in exceptions() (27.4.4.3), then the caught exception is rethrown.
Section: D.7.1.3 [depr.strstreambuf.virtuals] Status: DR Submitter: Matt Austern Date: 18 Aug 1998
D.7.1.3, paragraph 19, says that strstreambuf::setbuf "Performs an operation that is defined separately for each class derived from strstreambuf". This is obviously an incorrect cut-and-paste from basic_streambuf. There are no classes derived from strstreambuf.
Proposed resolution:
D.7.1.3 [depr.strstreambuf.virtuals], paragraph 19, replace the setbuf effects clause which currently says "Performs an operation that is defined separately for each class derived from strstreambuf" with:
Effects: implementation defined, except that setbuf(0,0) has no effect.
Section: 27.6.1.2.3 [lib.istream::extractors] Status: DR Submitter: Angelika Langer Date: 14 Jul 1998
Extractors for char* (27.6.1.2.3) do not store a null character after the extracted character sequence whereas the unformatted functions like get() do. Why is this?
Comment from Jerry Schwarz: There is apparently an editing glitch. You'll notice that the last item of the list of what stops extraction doesn't make any sense. It was supposed to be the line that said a null is stored.
Proposed resolution:
27.6.1.2.3 [lib.istream::extractors], paragraph 7, change the last list item from:
A null byte (charT()) in the next position, which may be the first position if no characters were extracted.
to become a new paragraph which reads:
Operator>> then stores a null byte (charT()) in the next position, which may be the first position if no characters were extracted.
Section: 23.2.4 [lib.vector] Status: DR Submitter: Andrew Koenig Date: 29 Jul 1998
The issue is this: Must the elements of a vector be in contiguous memory?
(Please note that this is entirely separate from the question of whether a vector iterator is required to be a pointer; the answer to that question is clearly "no," as it would rule out debugging implementations)
Proposed resolution:
Add the following text to the end of 23.2.4 [lib.vector], paragraph 1.
The elements of a vector are stored contiguously, meaning that if v is a vector<T, Allocator> where T is some type other than bool, then it obeys the identity &v[n] == &v[0] + n for all 0 <= n < v.size().
Rationale:
The LWG feels that as a practical matter the answer is clearly "yes". There was considerable discussion as to the best way to express the concept of "contiguous", which is not directly defined in the standard. Discussion included:
Section: 18.6 [lib.support.exception], 18.6.4 [lib.uncaught] Status: DR Submitter: Steve Clamage Date: Unknown
In article 3E04@pratique.fr, Valentin Bonnard writes:
uncaught_exception() doesn't have a throw specification.
It is intentional ? Does it means that one should be prepared to handle exceptions thrown from uncaught_exception() ?
uncaught_exception() is called in exception handling contexts where exception safety is very important.
Proposed resolution:
In 15.5.3 [except.uncaught], paragraph 1, 18.6 [lib.support.exception], and 18.6.4 [lib.uncaught], add "throw()" to uncaught_exception().
Section: 22.2.5.1 [lib.locale.time.get] Status: DR Submitter: Nathan Myers Date: 13 Aug 1998
The locale facet member time_get<>::do_get_monthname is described in 22.2.5.1.2 [lib.locale.time.get.virtuals] with five arguments, consistent with do_get_weekday and with its specified use by member get_monthname. However, in the synopsis, it is specified instead with four arguments. The missing argument is the "end" iterator value.
Proposed resolution:
In 22.2.5.1 [lib.locale.time.get], add an "end" argument to the declaration of member do_monthname as follows:
virtual iter_type do_get_monthname(iter_type s, iter_type end, ios_base&,
ios_base::iostate& err, tm* t) const;
Section: 22.2.1.5.2 [lib.locale.codecvt.virtuals] Status: DR Submitter: Matt Austern Date: 8 Sep 1998
The text of codecvt::do_max_length's "Returns" clause (22.2.1.5.2, paragraph 11) is garbled. It has unbalanced parentheses and a spurious n.
Proposed resolution:
Replace 22.2.1.5.2 [lib.locale.codecvt.virtuals] paragraph 11 with the following:
Returns: The maximum value that do_length(state, from, from_end, 1) can return for any valid range [from, from_end) and stateT value state. The specialization codecvt<char, char, mbstate_t>::do_max_length() returns 1.
Section: 22.2.1.5 [lib.locale.codecvt] Status: DR Submitter: Matt Austern Date: 18 Sep 1998
The class synopses for classes codecvt<> (22.2.1.5) and codecvt_byname<> (22.2.1.6) say that the first parameter of the member functions length and do_length is of type const stateT&. The member function descriptions, however (22.2.1.5.1, paragraph 6; 22.2.1.5.2, paragraph 9) say that the type is stateT&. Either the synopsis or the summary must be changed.
If (as I believe) the member function descriptions are correct, then we must also add text saying how do_length changes its stateT argument.
Proposed resolution:
In 22.2.1.5 [lib.locale.codecvt], and also in 22.2.1.6 [lib.locale.codecvt.byname], change the stateT argument type on both member length() and member do_length() from
const stateT&
to
stateT&
In 22.2.1.5.2 [lib.locale.codecvt.virtuals], add to the definition for member do_length a paragraph:
Effects: The effect on the state argument is ``as if'' it called do_in(state, from, from_end, from, to, to+max, to) for to pointing to a buffer of at least max elements.
Section: 27.4.2 [lib.ios.base] Status: DR Submitter: Nico Josuttis Date: 29 Sep 1998
typo: event_call_back should be event_callback
Proposed resolution:
In the 27.4.2 [lib.ios.base] synopsis change "event_call_back" to "event_callback".
Section: 26.2.1 [lib.complex.synopsis], 26.2.7 [lib.complex.value.ops] Status: DR Submitter: Nico Josuttis Date: 29 Sep 1998
In 26.2.1 [lib.complex.synopsis] polar is declared as follows:
template<class T> complex<T> polar(const T&, const T&);
In 26.2.7 [lib.complex.value.ops] it is declared as follows:
template<class T> complex<T> polar(const T& rho, const T& theta = 0);
Thus whether the second parameter is optional is not clear.
Proposed resolution:
In 26.2.1 [lib.complex.synopsis] change:
template<class T> complex<T> polar(const T&, const T&);
to:
template<class T> complex<T> polar(const T& rho, const T& theta = 0);
Section: 26.2.1 [lib.complex.synopsis], 26.2.2 [lib.complex] Status: DR Submitter: Nico Josuttis Date: 29 Sep 1998
Both 26.2.1 and 26.2.2 contain declarations of global operators for class complex. This redundancy should be removed.
Proposed resolution:
Reduce redundancy according to the general style of the standard.
Section: 21.3 [lib.basic.string] Status: DR Submitter: Nico Josuttis Date: 29 Sep 1998
Many string member functions throw if size is getting or exceeding npos. However, I wonder why they don't throw if size is getting or exceeding max_size() instead of npos. May be npos is known at compile time, while max_size() is known at runtime. However, what happens if size exceeds max_size() but not npos, then? It seems the standard lacks some clarifications here.
Proposed resolution:
After 21.3 [lib.basic.string] paragraph 4 ("The functions described in this clause...") add a new paragraph:
For any string operation, if as a result of the operation, size() would exceed max_size() then the operation throws length_error.
Rationale:
The LWG believes length_error is the correct exception to throw.
Section: 21.3.1 [lib.string.cons] Status: DR Submitter: Nico Josuttis Date: 29 Sep 1998
The constructor from a range:
template<class InputIterator>
basic_string(InputIterator begin, InputIterator end,
const Allocator& a = Allocator());
lacks a throws clause. However, I would expect that it throws according to the other constructors if the numbers of characters in the range equals npos (or exceeds max_size(), see above).
Proposed resolution:
In 21.3.1 [lib.string.cons], Strike throws paragraphs for constructors which say "Throws: length_error if n == npos."
Rationale:
Throws clauses for length_error if n == npos are no longer needed because they are subsumed by the general wording added by the resolution for issue 83.
Section: 21.3.7.9 [lib.string.io] Status: DR Submitter: Nico Josuttis Date: 29 Sep 1998
The effect of operator >> for strings contain the following item:
isspace(c,getloc()) is true for the next available input character c.
Here getloc() has to be replaced by is.getloc().
Proposed resolution:
In 21.3.7.9 paragraph 1 Effects clause replace:
isspace(c,getloc()) is true for the next available input character c.
with:
isspace(c,is.getloc()) is true for the next available input character c.
Section: 26.3.5 [lib.template.slice.array] Status: DR Submitter: AFNOR Date: 7 Oct 1998
This is the only place in the whole standard where the implementation has to document something private.
Proposed resolution:
Remove the comment which says "// remainder implementation defined" from:
Section: 18.6.1 [lib.exception] Status: DR Submitter: AFNOR Date: 7 Oct 1998
In 18.6.1, paragraphs 8-9, the lifetime of the return value of exception::what() is left unspecified. This issue has implications with exception safety of exception handling: some exceptions should not throw bad_alloc.
Proposed resolution:
Add to 18.6.1 [lib.exception] paragraph 9 (exception::what notes clause) the sentence:
The return value remains valid until the exception object from which it is obtained is destroyed or a non-const member function of the exception object is called.
Rationale:
If an exception object has non-const members, they may be used to set internal state that should affect the contents of the string returned by what().
Section: 24.5.3 [lib.istreambuf.iterator], 24.5.3.5 [lib.istreambuf.iterator::equal] Status: DR Submitter: Nathan Myers Date: 15 Oct 1998
Member istreambuf_iterator<>::equal is not declared "const", yet 24.5.3.6 [lib.istreambuf.iterator::op==] says that operator==, which is const, calls it. This is contradictory.
Proposed resolution:
In 24.5.3 [lib.istreambuf.iterator] and also in 24.5.3.5 [lib.istreambuf.iterator::equal], replace:
bool equal(istreambuf_iterator& b);
with:
bool equal(const istreambuf_iterator& b) const;
Section: 24.5.4.1 [lib.ostreambuf.iter.cons] Status: DR Submitter: Matt Austern Date: 20 Oct 1998
The requires clause for ostreambuf_iterator's constructor from an ostream_type (24.5.4.1, paragraph 1) reads "s is not null". However, s is a reference, and references can't be null.
Proposed resolution:
In 24.5.4.1 [lib.ostreambuf.iter.cons]:
Move the current paragraph 1, which reads "Requires: s is not null.", from the first constructor to the second constructor.
Insert a new paragraph 1 Requires clause for the first constructor reading:
Requires: s.rdbuf() is not null.
Section: 18.4.1.3 [lib.new.delete.placement] Status: DR Submitter: Steve Clamage Date: 28 Oct 1998
Section 18.4.1.3 contains the following example:
[Example: This can be useful for constructing an object at a known address:
char place[sizeof(Something)];
Something* p = new (place) Something();
-end example]
First code line: "place" need not have any special alignment, and the following constructor could fail due to misaligned data.
Second code line: Aren't the parens on Something() incorrect? [Dublin: the LWG believes the () are correct.]
Examples are not normative, but nevertheless should not show code that is invalid or likely to fail.
Proposed resolution:
Replace the first line of code in the example in 18.4.1.3 [lib.new.delete.placement] with:
void* place = operator new(sizeof(Something));
Section: D.7.4.1 [depr.strstream.cons] Status: DR Submitter: Steve Clamage Date: 2 Nov 1998
D.7.4.1 strstream constructors paragraph 2 says:
Effects: Constructs an object of class strstream, initializing the base class with iostream(& sb) and initializing sb with one of the two constructors:
- If mode&app==0, then s shall designate the first element of an array of n elements. The constructor is strstreambuf(s, n, s).
- If mode&app==0, then s shall designate the first element of an array of n elements that contains an NTBS whose first element is designated by s. The constructor is strstreambuf(s, n, s+std::strlen(s)).
Notice the second condition is the same as the first. I think the second condition should be "If mode&app==app", or "mode&app!=0", meaning that the append bit is set.
Proposed resolution:
In D.7.3.1 [depr.ostrstream.cons] paragraph 2 and D.7.4.1 [depr.strstream.cons] paragraph 2, change the first condition to (mode&app)==0 and the second condition to (mode&app)!=0.
Section: 17.4.4.8 [lib.res.on.exception.handling] Status: DR Submitter: Judy Ward Date: 15 Dec 1998
Section 17.4.4.8 [lib.res.on.exception.handling] states:
"An implementation may strengthen the exception-specification for a function by removing listed exceptions."
The problem is that if an implementation is allowed to do this for virtual functions, then a library user cannot write a class that portably derives from that class.
For example, this would not compile if ios_base::failure::~failure had an empty exception specification:
#include <ios>
#include <string>
class D : public std::ios_base::failure {
public:
D(const std::string&);
~D(); // error - exception specification must be compatible with
// overridden virtual function ios_base::failure::~failure()
};
Proposed resolution:
Change Section 17.4.4.8 [lib.res.on.exception.handling] from:
"may strengthen the exception-specification for a function"
to:
"may strengthen the exception-specification for a non-virtual function".
Section: 27.5.2 [lib.streambuf] Status: DR Submitter: Judy Ward Date: 15 Dec 1998
Section 27.5.2 describes the streambuf classes this way:
The class streambuf is a specialization of the template class basic_streambuf specialized for the type char.
The class wstreambuf is a specialization of the template class basic_streambuf specialized for the type wchar_t.
This implies that these classes must be template specializations, not typedefs.
It doesn't seem this was intended, since Section 27.5 has them declared as typedefs.
Proposed resolution:
Remove 27.5.2 [lib.streambuf] paragraphs 2 and 3 (the above two sentences).
Rationale:
The streambuf synopsis already has a declaration for the typedefs and that is sufficient.
Section: 22.2.1.2 [lib.locale.ctype.byname] Status: DR Submitter: Judy Ward Date: 15 Dec 1998
In Section 22.2.1.2 [lib.locale.ctype.byname] ctype_byname<charT>::do_scan_is() and do_scan_not() are declared to return a const char* not a const charT*.
Proposed resolution:
Change Section 22.2.1.2 [lib.locale.ctype.byname] do_scan_is() and do_scan_not() to return a const charT*.
Section: 26.3.2 [lib.template.valarray] Status: DR Submitter: Judy Ward Date: 15 Dec 1998
In Section 26.3.2 [lib.template.valarray] valarray<T>::operator!() is declared to return a valarray<T>, but in Section 26.3.2.5 [lib.valarray.unary] it is declared to return a valarray<bool>. The latter appears to be correct.
Proposed resolution:
Change in Section 26.3.2 [lib.template.valarray] the declaration of operator!() so that the return type is valarray<bool>.
Section: 22.2.1.1.2 [lib.locale.ctype.virtuals] Status: DR Submitter: Judy Ward Date: 15 Dec 1998
Typos in 22.2.1.1.2 need to be fixed.
Proposed resolution:
In Section 22.2.1.1.2 [lib.locale.ctype.virtuals] change:
do_widen(do_narrow(c),0) == c
to:
do_widen(do_narrow(c,0)) == c
and change:
(is(M,c) || !ctc.is(M, do_narrow(c),dfault) )
to:
(is(M,c) || !ctc.is(M, do_narrow(c,dfault)) )
Section: 20.4.5 [lib.auto.ptr] Status: DR Submitter: Greg Colvin Date: 17 Feb 1999
There are two problems with the current auto_ptr wording in the standard:
First, the auto_ptr_ref definition cannot be nested because auto_ptr<Derived>::auto_ptr_ref is unrelated to auto_ptr<Base>::auto_ptr_ref. Also submitted by Nathan Myers, with the same proposed resolution.
Second, there is no auto_ptr assignment operator taking an auto_ptr_ref argument.
I have discussed these problems with my proposal coauthor, Bill Gibbons, and with some compiler and library implementors, and we believe that these problems are not desired or desirable implications of the standard.
25 Aug 1999: The proposed resolution now reflects changes suggested by Dave Abrahams, with Greg Colvin's concurrence; 1) changed "assignment operator" to "public assignment operator", 2) changed effects to specify use of release(), 3) made the conversion to auto_ptr_ref const.
2 Feb 2000: Lisa Lippincott comments: [The resolution of] this issue states that the conversion from auto_ptr to auto_ptr_ref should be const. This is not acceptable, because it would allow initialization and assignment from _any_ const auto_ptr! It also introduces an implementation difficulty in writing this conversion function -- namely, somewhere along the line, a const_cast will be necessary to remove that const so that release() may be called. This may result in undefined behavior [7.1.5.1/4]. The conversion operator does not have to be const, because a non-const implicit object parameter may be bound to an rvalue [13.3.3.1.4/3] [13.3.1/5].
Tokyo: The LWG removed the following from the proposed resolution:
In 20.4.5 [lib.auto.ptr], paragraph 2, and 20.4.5.3 [lib.auto.ptr.conv], paragraph 2, make the conversion to auto_ptr_ref const:
template<class Y> operator auto_ptr_ref<Y>() const throw();
Proposed resolution:
In 20.4.5 [lib.auto.ptr], paragraph 2, move the auto_ptr_ref definition to namespace scope.
In 20.4.5 [lib.auto.ptr], paragraph 2, add a public assignment operator to the auto_ptr definition:
auto_ptr& operator=(auto_ptr_ref<X> r) throw();
Also add the assignment operator to 20.4.5.3 [lib.auto.ptr.conv]:
auto_ptr& operator=(auto_ptr_ref<X> r) throw()Effects: Calls reset(p.release()) for the auto_ptr p that r holds a reference to.
Returns: *this.
Section: 27.6.1.3 [lib.istream.unformatted], 27.6.2.4 [lib.ostream.seeks] Status: DR Submitter: Angelika Langer Date: 22 Feb 1999
Currently, the standard does not specify how seekg() and seekp() indicate failure. They are not required to set failbit, and they can't return an error indication because they must return *this, i.e. the stream. Hence, it is undefined what happens if they fail. And they can fail, for instance, when a file stream is disconnected from the underlying file (is_open()==false) or when a wide character file stream must perform a state-dependent code conversion, etc.
The stream functions seekg() and seekp() should set failbit in the stream state in case of failure.
Proposed resolution:
Add to the Effects: clause of seekg() in 27.6.1.3 [lib.istream.unformatted] and to the Effects: clause of seekp() in 27.6.2.4 [lib.ostream.seeks]:
In case of failure, the function calls setstate(failbit) (which may throw ios_base::failure).
Rationale:
Setting failbit is the usual error reporting mechanism for streams
Section: 23.2.2.2 [lib.list.capacity] Status: DR Submitter: Howard Hinnant Date: 6 Mar 1999
The description reads:
-1- Effects:
if (sz > size())
insert(end(), sz-size(), c);
else if (sz < size())
erase(begin()+sz, end());
else
; // do nothing
Obviously list::resize should not be specified in terms of random access iterators.
Proposed resolution:
Change 23.2.2.2 paragraph 1 to:
Effects:
if (sz > size())
insert(end(), sz-size(), c);
else if (sz < size())
{
iterator i = begin();
advance(i, sz);
erase(i, end());
}
[Dublin: The LWG asked Howard to discuss exception safety offline with David Abrahams. They had a discussion and believe there is no issue of exception safety with the proposed resolution.]
Section: 23.3.1 [lib.map] Status: DR Submitter: Howard Hinnant Date: 6 Mar 1999
The title says it all.
Proposed resolution:
Insert in 23.3.1 [lib.map], paragraph 2, after operator= in the map declaration:
allocator_type get_allocator() const;
Section: 23.2.4.1 [lib.vector.cons] Status: DR Submitter: Howard Hinnant Date: 6 Mar 1999
The complexity description says: "It does at most 2N calls to the copy constructor of T and logN reallocations if they are just input iterators ...".
This appears to be overly restrictive, dictating the precise memory/performance tradeoff for the implementor.
Proposed resolution:
Change 23.2.4.1 [lib.vector.cons], paragraph 1 to:
-1- Complexity: The constructor template <class InputIterator> vector(InputIterator first, InputIterator last) makes only N calls to the copy constructor of T (where N is the distance between first and last) and no reallocations if iterators first and last are of forward, bidirectional, or random access categories. It makes order N calls to the copy constructor of T and order logN reallocations if they are just input iterators.
Rationale:
"at most 2N calls" is correct only if the growth factor is greater than or equal to 2.
Section: 22.1.1 [lib.locale] Status: DR Submitter: Angelika Langer Date: 17 Mar 1999
Section 22.1.1 [lib.locale] says:
-4- In the call to use_facet<Facet>(loc), the type argument chooses a facet, making available all members of the named type. If Facet is not present in a locale (or, failing that, in the global locale), it throws the standard exception bad_cast. A C++ program can check if a locale implements a particular facet with the template function has_facet<Facet>().
This contradicts the specification given in section
22.1.2 [lib.locale.global.templates]:
template <class Facet> const Facet& use_facet(const
locale& loc);
-1- Get a reference to a facet of a locale.
-2- Returns: a reference to the corresponding facet of loc, if present.
-3- Throws: bad_cast if has_facet<Facet>(loc) is false.
-4- Notes: The reference returned remains valid at least as long as any copy of loc exists
Proposed resolution:
Remove the phrase "(or, failing that, in the global locale)" from section 22.1.1.
Rationale:
Needed for consistency with the way locales are handled elsewhere in the standard.
Section: 23.1.1 [lib.sequence.reqmts] Status: DR Submitter: Andrew Koenig Date: 30 Mar 1999
The sentence introducing the Optional sequence operation table (23.1.1 paragraph 12) has two problems:
A. It says ``The operations in table 68 are provided only for the containers for which
they take constant time.''
That could be interpreted in two ways, one of them being ``Even though table 68 shows
particular operations as being provided, implementations are free to omit them if they
cannot implement them in constant time.''
B. That paragraph says nothing about amortized constant time, and it should.
Proposed resolution:
Replace the wording in 23.1.1 paragraph 12 which begins ``The operations in table 68 are provided only..." with:
Table 68 lists sequence operations that are provided for some types of sequential containers but not others. An implementation shall provide these operations for all container types shown in the ``container'' column, and shall implement them so as to take amortized constant time.
Section: 21.3.6.4 [lib.string::find.last.of], 21.3.6.6 [lib.string::find.last.not.of] Status: DR Submitter: Arch Robison Date: 28 Apr 1999
Sections 21.3.6.4 paragraph 1 and 21.3.6.6 paragraph 1 surely have misprints where they
say:
— xpos <= pos and pos < size();
Surely the document meant to say ``xpos < size()'' in both places.
[Judy Ward also sent in this issue for 21.3.6.4 with the same proposed resolution.]
Proposed resolution:
Change Sections 21.3.6.4 paragraph 1 and 21.3.6.6 paragraph 1, the line which says:
— xpos <= pos and pos < size();
to:
— xpos <= pos and xpos < size();
Section: 25.3.8 [lib.alg.lex.comparison] Status: DR Submitter: Howard Hinnant Date: 20 Jun 1999
The lexicographical_compare complexity is specified as:
"At most min((last1 - first1), (last2 - first2))
applications of the corresponding comparison."
The best I can do is twice that expensive.
Nicolai Josuttis comments in lib-6862: You mean, to check for equality you have to check both < and >? Yes, IMO you are right! (and Matt states this complexity in his book)
Proposed resolution:
Change 25.3.8 [lib.alg.lex.comparison] complexity to:
At most 2*min((last1 - first1), (last2 - first2)) applications of the corresponding comparison.
Change the example at the end of paragraph 3 to read:
[Example:
for ( ; first1 != last1 && first2 != last2 ; ++first1, ++first2) {
if (*first1 < *first2) return true;
if (*first2 < *first1) return false;
}
return first1 == last1 && first2 != last2;
--end example]
Section: 23.2.1.1 [lib.deque.cons] Status: DR Submitter: Herb Sutter Date: 9 May 1999
In 23.2.1.1 paragraph 6, the deque ctor that takes an iterator range appears to have complexity requirements which are incorrect, and which contradict the complexity requirements for insert(). I suspect that the text in question, below, was taken from vector:
Complexity: If the iterators first and last are forward iterators, bidirectional iterators, or random access iterators the constructor makes only N calls to the copy constructor, and performs no reallocations, where N is last - first.
The word "reallocations" does not really apply to deque. Further, all of the following appears to be spurious:
It makes at most 2N calls to the copy constructor of T and log N reallocations if they are input iterators.1)
1) The complexity is greater in the case of input iterators because each element must be added individually: it is impossible to determine the distance between first abd last before doing the copying.
This makes perfect sense for vector, but not for deque. Why should deque gain an efficiency advantage from knowing in advance the number of elements to insert?
Proposed resolution:
In 23.2.1.1 paragraph 6, replace the Complexity description, including the footnote, with the following text (which also corrects the "abd" typo):
Complexity: Makes last - first calls to the copy constructor of T.
Section: 26.2.6 [lib.complex.ops] Status: DR Submitter: Angelika Langer Date: 12 May 1999
The extractor for complex numbers is specified as:
template<class T, class charT, class traits>
basic_istream<charT, traits>&
operator>>(basic_istream<charT, traits>& is, complex<T>& x);
Effects: Extracts a complex number x of the form: u, (u), or (u,v), where u is the real part and v is the imaginary part (lib.istream.formatted).
Requires: The input values be convertible to T. If bad input is encountered, calls is.setstate(ios::failbit) (which may throw ios::failure (lib.iostate.flags).
Returns: is .
Is it intended that the extractor for complex numbers does not skip
whitespace, unlike all other extractors in the standard library do?
Shouldn't a sentry be used?
The inserter for complex numbers is specified as:
template<class T, class charT, class traits>
basic_ostream<charT, traits>&
operator<<(basic_ostream<charT, traits>& o, const complex<T>& x);
Effects: inserts the complex number x onto the stream o as if it were implemented as follows:
template<class T, class charT, class traits>
basic_ostream<charT, traits>&
operator<<(basic_ostream<charT, traits>& o, const complex<T>& x)
{
basic_ostringstream<charT, traits> s;
s.flags(o.flags());
s.imbue(o.getloc());
s.precision(o.precision());
s << '(' << x.real() << "," << x.imag() << ')';
return o << s.str();
}
Is it intended that the inserter for complex numbers ignores the field width and does not do any padding? If, with the suggested implementation above, the field width were set in the stream then the opening parentheses would be adjusted, but the rest not, because the field width is reset to zero after each insertion.
I think that both operations should use sentries, for sake of consistency with the other inserters and extractors in the library. Regarding the issue of padding in the inserter, I don't know what the intent was.
Proposed resolution:
After 26.2.6 [lib.complex.ops] paragraph 14 (operator>>), add a Notes clause:
Notes: This extraction is performed as a series of simpler extractions. Therefore, the skipping of whitespace is specified to be the same for each of the simpler extractions.
Rationale:
For extractors, the note is added to make it clear that skipping whitespace follows an "all-or-none" rule.
For inserters, the LWG believes there is no defect; the standard is correct as written.
Section: 17.4.4.3 [lib.global.functions] Status: DR Submitter: Lois Goldthwaite Date: 4 Jun 1999
The library had many global functions until 17.4.1.1 [lib.contents] paragraph 2 was added:
All library entities except macros, operator new and operator delete are defined within the namespace std or namespaces nested within namespace std.
It appears "global function" was never updated in the following:
17.4.4.3 - Global functions [lib.global.functions]
-1- It is unspecified whether any global functions in the C++ Standard Library are defined as inline (dcl.fct.spec).
-2- A call to a global function signature described in Clauses lib.language.support through lib.input.output behaves the same as if the implementation declares no additional global function signatures.*
[Footnote: A valid C++ program always calls the expected library global function. An implementation may also define additional global functions that would otherwise not be called by a valid C++ program. --- end footnote]
-3- A global function cannot be declared by the implementation as taking additional default arguments.
17.4.4.4 - Member functions [lib.member.functions]
-2- An implementation can declare additional non-virtual member function signatures within a class:-- by adding arguments with default values to a member function signature; The same latitude does not extend to the implementation of virtual or global functions, however.
Proposed resolution:
Change "global" to "global or non-member" in:
17.4.4.3 [lib.global.functions] section title,
17.4.4.3 [lib.global.functions] para 1,
17.4.4.3 [lib.global.functions] para 2 in 2 places plus 2 places in the footnote,
17.4.4.3 [lib.global.functions] para 3,
17.4.4.4 [lib.member.functions] para 2
Rationale:
Because operator new and delete are global, the proposed resolution was changed from "non-member" to "global or non-member.
Section: 22.2.8 [lib.facets.examples] Status: DR Submitter: Jeremy Siek Date: 3 Jun 1999
In 22.2.8 [lib.facets.examples] paragraph 13, the do_truename() and do_falsename() functions in the example facet BoolNames should be const. The functions they are overriding in numpunct_byname<char> are const.
Proposed resolution:
In 22.2.8 [lib.facets.examples] paragraph 13, insert "const" in two places:
string do_truename() const { return "Oui Oui!"; }
string do_falsename() const { return "Mais Non!"; }
Section: 25.1.4 [lib.alg.find.first.of] Status: DR Submitter: Matt McClure Date: 30 Jun 1999
Proposed resolution:
Change 25.1.4 [lib.alg.find.first.of] paragraph 2 from:
Returns: The first iterator i in the range [first1, last1) such that for some integer j in the range [first2, last2) ...
to:
Returns: The first iterator i in the range [first1, last1) such that for some iterator j in the range [first2, last2) ...
Section: 23.1.1 [lib.sequence.reqmts] Status: DR Submitter: Ed Brey Date: 21 Jun 1999
For both sequences and associative containers, a.clear() has the
semantics of erase(a.begin(),a.end()), which is undefined for an empty
container since erase(q1,q2) requires that q1 be dereferenceable
(23.1.1,3 and 23.1.2,7). When the container is empty, a.begin() is
not dereferenceable.
The requirement that q1 be unconditionally dereferenceable causes many
operations to be intuitively undefined, of which clearing an empty
container is probably the most dire.
Since q1 and q2 are only referenced in the range [q1, q2), and [q1,
q2) is required to be a valid range, stating that q1 and q2 must be
iterators or certain kinds of iterators is unnecessary.
Proposed resolution:
In 23.1.1, paragraph 3, change:
p and q2 denote valid iterators to a, q and q1 denote valid dereferenceable iterators to a, [q1, q2) denotes a valid range
to:
p denotes a valid iterator to a, q denotes a valid dereferenceable iterator to a, [q1, q2) denotes a valid range in a
In 23.1.2, paragraph 7, change:
p and q2 are valid iterators to a, q and q1 are valid dereferenceable iterators to a, [q1, q2) is a valid range
to
p is a valid iterator to a, q is a valid dereferenceable iterator to a, [q1, q2) is a valid range into a
Section: 22.2.1.1.2 [lib.locale.ctype.virtuals] Status: DR Submitter: Dietmar Kühl Date: 20 Jul 1999
The semantics of scan_is() (paragraphs 4 and 6) is not exactly described because there is no function is() which only takes a character as argument. Also, in the effects clause (paragraph 3), the semantic is also kept vague.
Proposed resolution:
In 22.2.1.1.2 [lib.locale.ctype.virtuals] paragraphs 4 and 6, change the returns clause from:
"... such that is(*p) would..."
to: "... such that is(m, *p) would...."
Section: 22.2.2.1.2 [lib.facet.num.get.virtuals] Status: DR Submitter: Dietmar Kühl Date: 20 Jul 1999
The table in paragraph 7 for the length modifier does not list the length modifier l to be applied if the type is double. Thus, the standard asks the implementation to do undefined things when using scanf() (the missing length modifier for scanf() when scanning doubles is actually a problem I found quite often in production code, too).
Proposed resolution:
In 22.2.2.1.2 [lib.facet.num.get.virtuals], paragraph 7, add a row in the Length Modifier table to say that for double a length modifier l is to be used.
Rationale:
The standard makes an embarrassing beginner's mistake.
Section: 27.3 [lib.iostream.objects] Status: DR Submitter: Dietmar Kühl Date: 20 Jul 1999
There are conflicting statements about where the class Init is defined. According to 27.3 [lib.iostream.objects] paragraph 2 it is defined as basic_ios::Init, according to 27.4.2 [lib.ios.base] it is defined as ios_base::Init.
Proposed resolution:
Change 27.3 [lib.iostream.objects] paragraph 2 from "basic_ios::Init" to "ios_base::Init".
Rationale:
Although not strictly wrong, the standard was misleading enough to warrant the change.
Section: 27.4.2.3 [lib.ios.base.locales] Status: DR Submitter: Dietmar Kühl Date: 20 Jul 1999
There is a small discrepancy between the declarations of imbue(): in 27.4.2 [lib.ios.base] the argument is passed as locale const& (correct), in 27.4.2.3 [lib.ios.base.locales] it is passed as locale const (wrong).
Proposed resolution:
In 27.4.2.3 [lib.ios.base.locales] change the imbue argument from "locale const" to "locale const&".
Section: 27.5.2.4.2 [lib.streambuf.virt.buffer] Status: DR Submitter: Dietmar Kühl Date: 20 Jul 1999
The default behavior of setbuf() is described only for the situation that gptr() != 0 && gptr() != egptr(): namely to do nothing. What has to be done in other situations is not described although there is actually only one reasonable approach, namely to do nothing, too.
Since changing the buffer would almost certainly mess up most buffer management of derived classes unless these classes do it themselves, the default behavior of setbuf() should always be to do nothing.
Proposed resolution:
Change 27.5.2.4.2 [lib.streambuf.virt.buffer], paragraph 3, Default behavior, to: "Default behavior: Does nothing. Returns this."
Section: 27.5.2.4.3 [lib.streambuf.virt.get] Status: DR Submitter: Dietmar Kühl Date: 20 Jul 1999
The description of the meaning of the result of showmanyc() seems to be rather strange: It uses calls to underflow(). Using underflow() is strange because this function only reads the current character but does not extract it, uflow() would extract the current character. This should be fixed to use sbumpc() instead.
Proposed resolution:
Change 27.5.2.4.3 [lib.streambuf.virt.get] paragraph 1, showmanyc()returns clause, by replacing the word "supplied" with the words "extracted from the stream".
Section: 27.6.1.1 [lib.istream] Status: DR Submitter: Dietmar Kühl Date: 20 Jul 1999
The paragraph 4 refers to the function exception() which is not defined. Probably, the referred function is basic_ios<>::exceptions().
Proposed resolution:
In 27.6.1.1 [lib.istream], 27.6.1.3 [lib.istream.unformatted], paragraph 1, 27.6.2.1 [lib.ostream], paragraph 3, and 27.6.2.5.1 [lib.ostream.formatted.reqmts], paragraph 1, change "exception()" to "exceptions()".
[Note to Editor: "exceptions" with an "s" is the correct spelling.]
Section: 27.6.1.2.2 [lib.istream.formatted.arithmetic] Status: DR Submitter: Dietmar Kühl Date: 20 Jul 1999
The note in the second paragraph pretends that the first argument is an object of type istream_iterator. This is wrong: It is an object of type istreambuf_iterator.
Proposed resolution:
Change 27.6.1.2.2 [lib.istream.formatted.arithmetic] from:
The first argument provides an object of the istream_iterator class...
to
The first argument provides an object of the istreambuf_iterator class...
Section: 22.2.5.3.2 [lib.locale.time.put.virtuals] Status: DR Submitter: Angelika Langer Date: 23 Jul 1999
In 22.2.5.3.2 [lib.locale.time.put.virtuals] the do_put() function is specified
as taking a fill character as an argument, but the description of the
function does not say whether the character is used at all and, if so,
in which way. The same holds for any format control parameters that
are accessible through the ios_base& argument, such as the
adjustment or the field width. Is strftime() supposed to use the fill
character in any way? In any case, the specification of
time_put.do_put() looks inconsistent to me.
Is the
signature of do_put() wrong, or is the effects clause incomplete?
Proposed resolution:
Add the following note after 22.2.5.3.2 [lib.locale.time.put.virtuals] paragraph 2:
[Note: the fill argument may be used in the implementation-defined formats, or by derivations. A space character is a reasonable default for this argument. --end Note]
Rationale:
The LWG felt that while the normative text was correct, users need some guidance on what to pass for the fill argument since the standard doesn't say how it's used.
Section: 27.6.2.6 [lib.ostream.unformatted] Status: DR Submitter: Dietmar Kühl Date: 20 Jul 1999
The first paragraph begins with a descriptions what has to be done in formatted output functions. Probably this is a typo and the paragraph really want to describe unformatted output functions...
Proposed resolution:
In 27.6.2.6 [lib.ostream.unformatted] paragraph 1, the first and last sentences, change the word "formatted" to "unformatted":
"Each unformatted output function begins ..."
"... value specified for the unformatted output function."
Section: 27.7.1.3 [lib.stringbuf.virtuals] Status: DR Submitter: Dietmar Kühl Date: 20 Jul 1999
Paragraph 8, Notes, of this section seems to mandate an extremely inefficient way of buffer handling for basic_stringbuf, especially in view of the restriction that basic_ostream member functions are not allowed to use xsputn() (see 27.6.2.1 [lib.ostream]): For each character to be inserted, a new buffer is to be created.
Of course, the resolution below requires some handling of simultaneous input and output since it is no longer possible to update egptr() whenever epptr() is changed. A possible solution is to handle this in underflow().
Proposed resolution:
In 27.7.1.3 [lib.stringbuf.virtuals] paragraph 8, Notes, insert the words "at least" as in the following:
To make a write position available, the function reallocates (or initially allocates) an array object with a sufficient number of elements to hold the current array object (if any), plus at least one additional write position.
Section: 27.7.4 [lib.stringstream] Status: DR Submitter: Dietmar Kühl Date: 20 Jul 1999
The classes basic_stringstream (27.7.4 [lib.stringstream]), basic_istringstream (27.7.2 [lib.istringstream]), and basic_ostringstream (27.7.3 [lib.ostringstream]) are inconsistent in their definition of the type traits_type: For istringstream, this type is defined, for the other two it is not. This should be consistent.
Proposed resolution:
Proposed resolution:
To the declarations of basic_ostringstream (27.7.3 [lib.ostringstream]) and basic_stringstream (27.7.4 [lib.stringstream]) add:
typedef traits traits_type;
Section: 27.6.1.3 [lib.istream.unformatted] Status: DR Submitter: Greg Comeau, Dietmar Kühl Date: 23 Jul 1999
In 27.6.1.1 [lib.istream] the function ignore() gets an object of type streamsize as first argument. However, in 27.6.1.3 [lib.istream.unformatted] paragraph 23 the first argument is of type int.
As far as I can see this is not really a contradiction because everything is consistent if streamsize is typedef to be int. However, this is almost certainly not what was intended. The same thing happened to basic_filebuf::setbuf(), as described in issue 173.
Darin Adler also submitted this issue, commenting: Either 27.6.1.1 should be modified to show a first parameter of type int, or 27.6.1.3 should be modified to show a first parameter of type streamsize and use numeric_limits<streamsize>::max.
Proposed resolution:
In 27.6.1.3 [lib.istream.unformatted] paragraph 23 and 24, change both uses of int in the description of ignore() to streamsize.
Section: 27.8.1.4 [lib.filebuf.virtuals] Status: DR Submitter: Greg Comeau, Dietmar Kühl Date: 23 Jul 1999
In 27.8.1.1 [lib.filebuf] the function setbuf() gets an object of type streamsize as second argument. However, in 27.8.1.4 [lib.filebuf.virtuals] paragraph 9 the second argument is of type int.
As far as I can see this is not really a contradiction because everything is consistent if streamsize is typedef to be int. However, this is almost certainly not what was intended. The same thing happened to basic_istream::ignore(), as described in issue 172.
Proposed resolution:
In 27.8.1.4 [lib.filebuf.virtuals] paragraph 9, change all uses of int in the description of setbuf() to streamsize.
Section: D.6 [depr.ios.members] Status: DR Submitter: Dietmar Kühl Date: 23 Jul 1999
According to paragraph 1 of this section, streampos is the type OFF_T, the same type as streamoff. However, in paragraph 6 the streampos gets the type POS_T
Proposed resolution:
Change D.6 [depr.ios.members] paragraph 1 from "typedef OFF_T streampos;" to "typedef POS_T streampos;"
Section: D.6 [depr.ios.members] Status: DR Submitter: Dietmar Kühl Date: 23 Jul 1999
According to paragraph 8 of this section, the methods basic_streambuf::pubseekpos(), basic_ifstream::open(), and basic_ofstream::open "may" be overloaded by a version of this function taking the type ios_base::open_mode as last argument argument instead of ios_base::openmode (ios_base::open_mode is defined in this section to be an alias for one of the integral types). The clause specifies, that the last argument has a default argument in three cases. However, this generates an ambiguity with the overloaded version because now the arguments are absolutely identical if the last argument is not specified.
Proposed resolution:
In D.6 [depr.ios.members] paragraph 8, remove the default arguments for basic_streambuf::pubseekpos(), basic_ifstream::open(), and basic_ofstream::open().
Section: D.6 [depr.ios.members] Status: DR Submitter: Dietmar Kühl Date: 23 Jul 1999
The "overload" for the function exceptions() in paragraph 8 gives the impression that there is another function of this function defined in class ios_base. However, this is not the case. Thus, it is hard to tell how the semantics (paragraph 9) can be implemented: "Call the corresponding member function specified in clause 27 [lib.input.output]."
Proposed resolution:
In D.6 [depr.ios.members] paragraph 8, move the declaration of the function exceptions()into class basic_ios.
Section: 20.2.2 [lib.pairs] Status: DR Submitter: Andrew Koenig Date: 3 Aug 1999
The claim has surfaced in Usenet that expressions such as
make_pair("abc", 3)
are illegal, notwithstanding their use in examples, because template instantiation tries to bind the first template
parameter to const char (&)[4], which type is uncopyable.
I doubt anyone intended that behavior...
Proposed resolution:
In 20.2 [lib.utility], paragraph 1 change the following declaration of make_pair():
template <class T1, class T2> pair<T1,T2> make_pair(const T1&, const T2&);
to:
template <class T1, class T2> pair<T1,T2> make_pair(T1, T2);
In 20.2.2 [lib.pairs] paragraph 7 and the line before, change:
template <class T1, class T2> pair<T1, T2> make_pair(const T1& x, const T2& y);
to:
template <class T1, class T2> pair<T1, T2> make_pair(T1 x, T2 y);
and add the following footnote to the effects clause:
According to 12.8 [class.copy], an implementation is permitted to not perform a copy of an argument, thus avoiding unnecessary copies.
Rationale:
Two potential fixes were suggested by Matt Austern and Dietmar Kühl, respectively, 1) overloading with array arguments, and 2) use of a reference_traits class with a specialization for arrays. Andy Koenig suggested changing to pass by value. In discussion, it appeared that this was a much smaller change to the standard that the other two suggestions, and any efficiency concerns were more than offset by the advantages of the solution. Two implementors reported that the proposed resolution passed their test suites.
Section: 27.4.2.2 [lib.fmtflags.state] Status: DR Submitter: Andrew Koenig Date: 25 Aug 1999
27.4.2.2 paragraph 9 claims that setprecision() sets the precision,
and includes a parenthetical note saying that it is the number of
digits after the decimal point.
This claim is not strictly correct. For example, in the default
floating-point output format, setprecision sets the number of
significant digits printed, not the number of digits after the decimal
point.
I would like the committee to look at the definition carefully and
correct the statement in 27.4.2.2
Proposed resolution:
Remove from 27.4.2.2 [lib.fmtflags.state], paragraph 9, the text "(number of digits after the decimal point)".
Section: 25.3.6 [lib.alg.heap.operations] Status: DR Submitter: Markus Mauhart Date: 24 Sep 1999
25.3.6 [lib.alg.heap.operations] states two key properties of a heap [a,b), the first of them
is
`"(1) *a is the largest element"
I think this is incorrect and should be changed to the wording in the proposed
resolution.
Actually there are two independent changes:
A-"part of largest equivalence class" instead of "largest", cause 25.3 [lib.alg.sorting] asserts "strict weak ordering" for all its sub clauses.
B-Take 'an oldest' from that equivalence class, otherwise the heap functions could not be used for a priority queue as explained in 23.2.3.2.2 [lib.priqueue.members] (where I assume that a "priority queue" respects priority AND time).
Proposed resolution:
Change 25.3.6 [lib.alg.heap.operations] property (1) from:
(1) *a is the largest element
to:
(1) There is no element greater than *a
Section: 27.6.1.1.2 [lib.istream::sentry] Status: DR Submitter: Matt Austern Date: 13 Oct 1999
Suppose that is.flags() & ios_base::skipws is nonzero. What should basic_istream<>::sentry's constructor do if it reaches eof while skipping whitespace? 27.6.1.1.2/5 suggests it should set failbit. Should it set eofbit as well? The standard doesn't seem to answer that question.
On the one hand, nothing in 27.6.1.1.2 [lib.istream::sentry] says that basic_istream<>::sentry should ever set eofbit. On the other hand, 27.6.1.1 [lib.istream] paragraph 4 says that if extraction from a streambuf "returns traits::eof(), then the input function, except as explicitly noted otherwise, completes its actions and does setstate(eofbit)". So the question comes down to whether basic_istream<>::sentry's constructor is an input function.
Comments from Jerry Schwarz:
It was always my intention that eofbit should be set any time that a virtual returned something to indicate eof, no matter what reason iostream code had for calling the virtual.
The motivation for this is that I did not want to require streambufs to behave consistently if their virtuals are called after they have signaled eof.
The classic case is a streambuf reading from a UNIX file. EOF isn't really a state for UNIX file descriptors. The convention is that a read on UNIX returns 0 bytes to indicate "EOF", but the file descriptor isn't shut down in any way and future reads do not necessarily also return 0 bytes. In particular, you can read from tty's on UNIX even after they have signaled "EOF". (It isn't always understood that a ^D on UNIX is not an EOF indicator, but an EOL indicator. By typing a "line" consisting solely of ^D you cause a read to return 0 bytes, and by convention this is interpreted as end of file.)
Proposed resolution:
Add a sentence to the end of 27.6.1.1.2 paragraph 2:
If is.rdbuf()->sbumpc() or is.rdbuf()->sgetc() returns traits::eof(), the function calls setstate(failbit | eofbit) (which may throw ios_base::failure).
Section: 20.1.5 [lib.allocator.requirements] Status: DR Submitter: Matt Austern Date: 19 Nov 1999
Suppose that A is a class that conforms to the Allocator requirements of Table 32, and a is an object of class A What should be the return value of a.allocate(0)? Three reasonable possibilities: forbid the argument 0, return a null pointer, or require that the return value be a unique non-null pointer.
Proposed resolution:
Add a note to the allocate row of Table 32: "[Note: If n == 0, the return value is unspecified. --end note]"
Rationale:
A key to understanding this issue is that the ultimate use of allocate() is to construct an iterator, and that iterator for zero length sequences must be the container's past-the-end representation. Since this already implies special case code, it would be over-specification to mandate the return value.
Section: 24.1 [lib.iterator.requirements] Status: DR Submitter: Stephen Cleary Date: 02 Feb 2000
In 24.1 paragraph 5, it is stated ". . . Dereferenceable and past-the-end values are always non-singular."
This places an unnecessary restriction on past-the-end iterators for containers with forward iterators (for example, a singly-linked list). If the past-the-end value on such a container was a well-known singular value, it would still satisfy all forward iterator requirements.
Removing this restriction would allow, for example, a singly-linked list without a "footer" node.
This would have an impact on existing code that expects past-the-end iterators obtained from different (generic) containers being not equal.
Proposed resolution:
Change 24.1 [lib.iterator.requirements] paragraph 5, the last sentence, from:
Dereferenceable and past-the-end values are always non-singular.
to:
Dereferenceable values are always non-singular.
Rationale:
For some kinds of containers, including singly linked lists and zero-length vectors, null pointers are perfectly reasonable past-the-end iterators. Null pointers are singular.
Section: 21.3 [lib.basic.string] Status: DR Submitter: Igor Stauder Date: 11 Feb 2000
In Section 21.3 [lib.basic.string] the basic_string member function declarations use a consistent style except for the following functions:
void push_back(const charT); basic_string& assign(const basic_string&); void swap(basic_string<charT,traits,Allocator>&);
- push_back, assign, swap: missing argument name
- push_back: use of const with charT (i.e. POD type passed by value
not by reference - should be charT or const charT& )
- swap: redundant use of template parameters in argument
basic_string<charT,traits,Allocator>&
Proposed resolution:
In Section 21.3 [lib.basic.string] change the basic_string member function declarations push_back, assign, and swap to:
void push_back(charT c); basic_string& assign(const basic_string& str); void swap(basic_string& str);
Rationale:
Although the standard is in general not consistent in declaration style, the basic_string declarations are consistent other than the above. The LWG felt that this was sufficient reason to merit the change.
Section: 25 [lib.algorithms] Status: DR Submitter: Lisa Lippincott Date: 15 Feb 2000
In paragraph 9 of section 25 [lib.algorithms], it is written:
In the description of the algorithms operators + and - are used for some of the iterator categories for which they do not have to be defined. In these cases the semantics of [...] a-b is the same as of
return distance(a, b);
Proposed resolution:
On the last line of paragraph 9 of section 25 [lib.algorithms] change "a-b" to "b-a".
Rationale:
There are two ways to fix the defect; change the description to b-a or change the return to distance(b,a). The LWG preferred the former for consistency.
Section: 21.3.7.9 [lib.string.io] Status: DR Submitter: Scott Snyder Date: 4 Feb 2000
The description of the stream extraction operator for std::string (section 21.3.7.9 [lib.string.io]) does not contain a requirement that failbit be set in the case that the operator fails to extract any characters from the input stream.
This implies that the typical construction
std::istream is; std::string str; ... while (is >> str) ... ;
(which tests failbit) is not required to terminate at EOF.
Furthermore, this is inconsistent with other extraction operators, which do include this requirement. (See sections 27.6.1.2 [lib.istream.formatted] and 27.6.1.3 [lib.istream.unformatted]), where this requirement is present, either explicitly or implicitly, for the extraction operators. It is also present explicitly in the description of getline (istream&, string&, charT) in section 21.3.7.9 [lib.string.io] paragraph 8.)
Proposed resolution:
Insert new paragraph after paragraph 2 in section 21.3.7.9 [lib.string.io]:
If the function extracts no characters, it calls is.setstate(ios::failbit) which may throw ios_base::failure (27.4.4.3).
Section: 25.3.7 [lib.alg.min.max] Status: DR Submitter: Nico Josuttis Date: 26 Feb 2000
The standard doesn't specify what min_element() and max_element() shall return if the range is empty (first equals last). The usual implementations return last. This problem seems also apply to partition(), stable_partition(), next_permutation(), and prev_permutation().
Proposed resolution:
In 25.3.7 [lib.alg.min.max] - Minimum and maximum, paragraphs 7 and 9, append: Returns last if first==last.
Rationale:
The LWG looked in some detail at all of the above mentioned algorithms, but believes that except for min_element() and max_element() it is already clear that last is returned if first == last.
Section: 22.2.8 [lib.facets.examples] Status: DR Submitter: Martin Sebor Date: 29 Feb 2000
The example in 22.2.8, paragraph 11 contains the following errors:
1) The member function `My::JCtype::is_kanji()' is non-const; the function must be const in order for it to be callable on a const object (a reference to which which is what std::use_facet<>() returns).
2) In file filt.C, the definition of `JCtype::id' must be qualified with the name of the namespace `My'.
3) In the definition of `loc' and subsequently in the call to use_facet<>() in main(), the name of the facet is misspelled: it should read `My::JCtype' rather than `My::JCType'.
Proposed resolution:
Replace the "Classifying Japanese characters" example in 22.2.8, paragraph 11 with the following:
#include <locale>
namespace My {
using namespace std;
class JCtype : public locale::facet {
public:
static locale::id id; // required for use as a new locale facet
bool is_kanji (wchar_t c) const;
JCtype() {}
protected:
~JCtype() {}
};
}
// file: filt.C #include <iostream> #include <locale> #include "jctype" // above std::locale::id My::JCtype::id; // the static JCtype member declared above.
int main()
{
using namespace std;
typedef ctype<wchar_t> wctype;
locale loc(locale(""), // the user's preferred locale...
new My::JCtype); // and a new feature ...
wchar_t c = use_facet<wctype>(loc).widen('!');
if (!use_facet<My::JCtype>(loc).is_kanji(c))
cout << "no it isn't!" << endl;
return 0;
}
Section: 27.4.2.7 [lib.ios.base.cons] Status: DR Submitter: Jonathan Schilling, Howard Hinnant Date: 13 Mar 2000
The pre-conditions for the ios_base destructor are described in 27.4.2.7 paragraph 2:
Effects: Destroys an object of class ios_base. Calls each registered callback pair (fn,index) (27.4.2.6) as (*fn)(erase_event,*this,index) at such time that any ios_base member function called from within fn has well defined results.
But what is not clear is: If no callback functions were ever registered, does it matter whether the ios_base members were ever initialized?
For instance, does this program have defined behavior:
#include <ios>class D : public std::ios_base { };int main() { D d; }
It seems that registration of a callback function would surely affect the state of an ios_base. That is, when you register a callback function with an ios_base, the ios_base must record that fact somehow.
But if after construction the ios_base is in an indeterminate state, and that state is not made determinate before the destructor is called, then how would the destructor know if any callbacks had indeed been registered? And if the number of callbacks that had been registered is indeterminate, then is not the behavior of the destructor undefined?
By comparison, the basic_ios class description in 27.4.4.1 paragraph 2 makes it explicit that destruction before initialization results in undefined behavior.
Proposed resolution:
Modify 27.4.2.7 paragraph 1 from
Effects: Each ios_base member has an indeterminate value after construction.
to
Effects: Each ios_base member has an indeterminate value after construction. These members must be initialized by calling basic_ios::init. If an ios_base object is destroyed before these initializations have taken place, the behavior is undefined.
Section: 17.3.1.3 [lib.structure.specifications] Status: DR Submitter: Judy Ward Date: 17 Mar 2000
Section 21.3.6.8 describes the basic_string::compare function this way:
21.3.6.8 - basic_string::compare [lib.string::compare]
int compare(size_type pos1, size_type n1,
const basic_string<charT,traits,Allocator>& str ,
size_type pos2 , size_type n2 ) const;
-4- Returns:
basic_string<charT,traits,Allocator>(*this,pos1,n1).compare(
basic_string<charT,traits,Allocator>(str,pos2,n2)) .
and the constructor that's implicitly called by the above is defined to throw an out-of-range exception if pos > str.size(). See section 21.3.1 [lib.string.cons] paragraph 4.
On the other hand, the compare function descriptions themselves don't have "Throws: " clauses and according to 17.3.1.3, paragraph 3, elements that do not apply to a function are omitted.
So it seems there is an inconsistency in the standard -- are the "Effects" clauses correct, or are the "Throws" clauses missing?
Proposed resolution:
In 17.3.1.3 [lib.structure.specifications] paragraph 3, the footnote 148 attached to the sentence "Descriptions of function semantics contain the following elements (as appropriate):", insert the word "further" so that the foot note reads:
To save space, items that do not apply to a function are omitted. For example, if a function does not specify any further preconditions, there will be no "Requires" paragraph.
Rationale:
The standard is somewhat inconsistent, but a failure to note a throw condition in a throws clause does not grant permission not to throw. The inconsistent wording is in a footnote, and thus non-normative. The proposed resolution from the LWG clarifies the footnote.
Section: 25.2.9 [lib.alg.reverse] Status: DR Submitter: Dave Abrahams Date: 21 Mar 2000
Shouldn't the effects say "applies iter_swap to all pairs..."?
Proposed resolution:
In 25.2.9 [lib.alg.reverse], replace:
Effects: For each non-negative integer i <= (last - first)/2, applies swap to all pairs of iterators first + i, (last - i) - 1.
with:
Effects: For each non-negative integer i <= (last - first)/2, applies iter_swap to all pairs of iterators first + i, (last - i) - 1.
Section: 23.1.2 [lib.associative.reqmts] Status: DR Submitter: Ed Brey Date: 23 Mar 2000
In the associative container requirements table in 23.1.2 paragraph 7, a.clear() has complexity "log(size()) + N". However, the meaning of N is not defined.
Proposed resolution:
In the associative container requirements table in 23.1.2 paragraph 7, the complexity of a.clear(), change "log(size()) + N" to "linear in size()".
Rationale:
It's the "log(size())", not the "N", that is in error: there's no difference between O(N) and O(N + log(N)). The text in the standard is probably an incorrect cut-and-paste from the range version of erase.
Section: 25.2.2 [lib.alg.swap] Status: DR Submitter: Dave Abrahams Date: 09 Apr 2000
25.2.2 reads:
template<class T> void swap(T& a, T& b);
Requires: Type T is Assignable (_lib.container.requirements_).
Effects: Exchanges values stored in two locations.
The only reasonable** generic implementation of swap requires construction of a new temporary copy of one of its arguments:
template<class T> void swap(T& a, T& b);
{
T tmp(a);
a = b;
b = tmp;
}
But a type which is only Assignable cannot be swapped by this implementation.
**Yes, there's also an unreasonable implementation which would require T to be DefaultConstructible instead of CopyConstructible. I don't think this is worthy of consideration:
template<class T> void swap(T& a, T& b);
{
T tmp;
tmp = a;
a = b;
b = tmp;
}
Proposed resolution:
Change 25.2.2 paragraph 1 from:
Requires: Type T is Assignable (23.1).
to:
----- End of document -----Requires: Type T is CopyConstructible (20.1.3) and Assignable (23.1)