______________________________________________________________________
Annex D (normative)
Compatibility features [depr]
______________________________________________________________________
1 This Clause describes features of the C++ Standard that are specified
for compatibility with existing implementations.
+------- BEGIN BOX 1 -------+
Editorial proposal: Specify these as deprecated features, where depre
cated is defined as:
Normative for the current edition of the Standard, but are not guaran
teed to be part of the Standard in future revisions.
+------- END BOX 1 -------+
D.1 Standard C library headers [depr.c.headers]
1 For compatibility with the Standard C library, the C++ Standard
library provides the 18 C headers, as shown in Table 1:
Table 1--C Headers
<assert.h> <iso646.h> <setjmp.h> <stdio.h> <wchar.h>
<ctype.h> <limits.h> <signal.h> <stdlib.h> <wctype.h>
<errno.h> <locale.h> <stdarg.h> <string.h>
<float.h> <math.h> <stddef.h> <time.h>
2 Each C header, whose name has the form name.h, includes its corre
sponding C++ header cname, followed by an explicit using-declaration
(_namespace.udecl_) for each name placed in the standard library
namespace by the header (_lib.headers_).
3 [Example: The header <cstdlib> provides its declarations and defini
tions within the namespace std. The header <stdlib.h> makes these
available in the global name space, much as in the C Standard. --end
example]
+------- BEGIN BOX 2 -------+
Editorial proposal: Add the following paragraph:
The C++ headers
--<iostream.h> and
--<strstream.h>
are similarly available.
+------- END BOX 2 -------+
D.2 Old iostreams members [depr.ios.members]
1 The following member names are in addition to names specified in
Clause _lib.iostreams_:
namespace std {
class ios_base {
public:
typedef T1 io_state;
typedef T2 open_mode;
typedef T3 seek_dir;
// remainder unchanged
};
}
2 The type io_state is a synonym for an integer type (indicated here as
T1) that permits certain member functions to overload others on param
eters of type iostate and provide the same behavior.
3 The type open_mode is a synonym for an integer type (indicated here as
T2) that permits certain member functions to overload others on param
eters of type openmode and provide the same behavior.
4 The type seek_dir is a synonym for an integer type (indicated here as
T3) that permits certain member functions to overload others on param
eters of type iostate and provide the same behavior.
5 An implementation may provide the following additional member func
tion, which has the effect of calling sbumpc()
(_lib.streambuf.pub.get_):
namespace std {
template<class charT, class traits = ios_traits<charT> >
class basic_streambuf {
public:
void stossc();
// remainder unchanged
};
}
6 An implementation may provide the following member functions that
overload signatures specified in Clause _lib.iostreams_:
namespace std {
template<class charT, class Traits> class basic_ios {
public:
void clear(io_state state);
void setstate(io_state state);
// remainder unchanged
};
class ios_base {
public:
void exceptions(io_state);
// remainder unchanged
};
template<class charT, class traits = ios_traits<charT> >
class basic_streambuf {
public:
pos_type pubseekoff(off_type off, ios_base::seek_dir way,
ios_base::open_mode which = ios_base::in | ios_base::out);
pos_type pubseekpos(pos_type sp,
ios_base::open_mode which = ios_base::in | ios_base::out);
// remainder unchanged
};
template <class charT, class traits = ios_traits<charT> >
class basic_filebuf : public basic_streambuf<charT,traits> {
public:
basic_filebuf<charT,traits>* open(const char* s, ios_base::open_mode mode);
// remainder unchanged
};
template <class charT, class traits = file_traits<charT> >
class basic_ifstream : public basic_istream<charT,traits> {
public:
void open(const char* s, open_mode mode = in);
// remainder unchanged
};
template <class charT, class traits = file_traits<charT> >
class basic_ofstream : public basic_ostream<charT,traits> {
public:
void open(const char* s, ios_base::open_mode mode = out | trunc);
// remainder unchanged
};
}
7 The effects of these functions is to call the corresponding member
function specified in Clause _lib.iostreams_.
+------- BEGIN BOX 3 -------+
ISSUE: Were these intended to be allowed in the template, or only in
the specializations for char?
+------- END BOX 3 -------+
D.3 char* streams [depr.str.strstreams]
1 The header <strstream> (and, as per _depr.c.headers_, <strstream.h>)
defines three types that associate stream buffers with character array
objects and assist reading and writing such objects.
D.3.1 Class strstreambuf [depr.strstreambuf]
namespace std {
class strstreambuf : public streambuf<char> {
public:
explicit strstreambuf(streamsize alsize_arg = 0);
strstreambuf(void* (*palloc_arg)(size_t), void (*pfree_arg)(void*));
strstreambuf(char* gnext_arg, streamsize n, char* pbeg_arg = 0);
strstreambuf(const char* gnext_arg, streamsize n);
strstreambuf(signed char* gnext_arg, streamsize n,
signed char* pbeg_arg = 0);
strstreambuf(const signed char* gnext_arg, streamsize n);
strstreambuf(unsigned char* gnext_arg, streamsize n,
unsigned char* pbeg_arg = 0);
strstreambuf(const unsigned char* gnext_arg, streamsize n);
virtual ~strstreambuf();
void freeze(bool = 1);
char* str();
int pcount();
protected:
virtual int_type overflow (int_type c = ios_traits<char>::eof());
virtual int_type pbackfail(int_type c = ios_traits<char>::eof());
virtual int_type underflow();
virtual pos_type seekoff(off_type off, ios_base::seekdir way,
ios_base::openmode which
= ios_base::in | ios_base::out);
virtual pos_type seekpos(pos_type sp, ios_base::openmode which
= ios_base::in | ios_base::out);
virtual streambuf<char>* setbuf(char* s, streamsize n);
private:
// typedef T1 strstate; exposition only
// static const strstate allocated; exposition only
// static const strstate constant; exposition only
// static const strstate dynamic; exposition only
// static const strstate frozen; exposition only
// strstate strmode; exposition only
// streamsize alsize; exposition only
// void* (*palloc)(size_t); exposition only
// void (*pfree)(void*); exposition only
};
}
+------- BEGIN BOX 4 -------+
The following members were removed, even though they appeared on p. 45
of 94-0083/N0470 and p. 27-78 of the 20 Sep 94 Working Paper, and no
Resolution specifically called for their removal:
typedef charT char_type;
typedef traits::int_type int_type;
typedef traits::pos_type pos_type;
typedef traits::off_type off_type;
int_type eof() { return traits::eof(); }
char_type newline() { return traits::newline(); }
The following members were added, even though they did not appear in
94-0083/N0470:
strstreambuf(signed char* gnext_arg, streamsize n,
signed char* pbeg_arg = 0);
strstreambuf(const signed char* gnext_arg, streamsize n);
strstreambuf(unsigned char* gnext_arg, streamsize n,
unsigned char* pbeg_arg = 0);
strstreambuf(const unsigned char* gnext_arg, streamsize n);
+------- END BOX 4 -------+
1 The class strstreambuf associates the input sequence, and possibly the
output sequence, with an object of some character array type, whose
elements store arbitrary values. The array object has several
attributes.
2 [Note: For the sake of exposition, these are represented as elements
of a bitmask type (indicated here as T1) called strstate. The ele
ments are:
--allocated, set when a dynamic array object has been allocated, and
hence should be freed by the destructor for the strstreambuf object;
--constant, set when the array object has const elements, so the out
put sequence cannot be written;
--dynamic, set when the array object is allocated (or reallocated) as
necessary to hold a character sequence that can change in length;
--frozen, set when the program has requested that the array object not
be altered, reallocated, or freed. --end note]
3 [Note: For the sake of exposition, the maintained data is presented
here as:
--strstate strmode, the attributes of the array object associated with
the strstreambuf object;
--int alsize, the suggested minimum size for a dynamic array object;
--void* (*palloc)(size_t), points to the function to call to allocate
a dynamic array object;
--void (*pfree)(void*), points to the function to call to free a
dynamic array object. --end note]
4 Each object of class strstreambuf has a seekable area, delimited by
the pointers seeklow and seekhigh. If gnext is a null pointer, the
seekable area is undefined. Otherwise, seeklow equals gbeg and
seekhigh is either pend, if pend is not a null pointer, or gend.
D.3.1.1 strstreambuf constructors [depr.strstreambuf.cons]
explicit strstreambuf(streamsize alsize_arg = 0);
Effects:
Constructs an object of class strstreambuf, initializing the base
class with streambuf().
The postconditions of this function are indicated in Table 2:
Table 2--strstreambuf(streamsize) effects
+-------------------------+
|Element Value |
+-------------------------+
|strmode dynamic |
|alsize alsize_arg |
|palloc a null pointer |
|pfree a null pointer |
+-------------------------+
strstreambuf(void* (*palloc_arg)(size_t), void (*pfree_arg)(void*));
Effects:
Constructs an object of class strstreambuf, initializing the base
class with streambuf().
The postconditions of this function are indicated in Table 3:
Table 3--strstreambuf(void* (*)(size_t),void (*)(void*) effects
+-------------------------------+
|Element Value |
+-------------------------------+
|strmode dynamic |
|alsize an unspecified value |
|palloc palloc_arg |
|pfree pfree_arg |
+-------------------------------+
strstreambuf(char* gnext_arg, streamsize n, char *pbeg_arg = 0);
strstreambuf(signed char* gnext_arg, streamsize n,
signed char *pbeg_arg = 0);
strstreambuf(unsigned char* gnext_arg, streamsize n,
unsigned char *pbeg_arg = 0);
Effects:
Constructs an object of class strstreambuf, initializing the base
class with streambuf().
The postconditions of this function are indicated in Table 4:
Table 4--strstreambuf(charT*,streamsize,charT*) effects
+-------------------------------+
|Element Value |
+-------------------------------+
|strmode 0 |
|alsize an unspecified value |
|palloc a null pointer |
|pfree a null pointer |
+-------------------------------+
1 gnext_arg shall point to the first element of an array object whose
number of elements N is determined as follows:
--If n > 0, N is n.
--If n == 0, N is ::strlen(gnext_arg).
--If n < 0, N is INT_MAX.1)
2 If pbeg_arg is a null pointer, the function executes:
setg(gnext_arg, gnext_arg, gnext_arg + N);
3 Otherwise, the function executes:
setg(gnext_arg, gnext_arg, pbeg_arg);
setp(pbeg_arg, pbeg_arg + N);
strstreambuf(const char* gnext_arg, streamsize n);
strstreambuf(const signed char* gnext_arg, streamsize n);
strstreambuf(const unsigned char* gnext_arg, streamsize n);
Effects:
Behaves the same as strstreambuf((char*)gnext_arg,n), except that
the constructor also sets constant in strmode.
_________________________
1) The function signature strlen(const char*) is declared in
<cstring>. (_lib.c.strings_). The macro INT_MAX is defined in
<climits> (_lib.support.limits_).
virtual ~strstreambuf();
Effects:
Destroys an object of class strstreambuf. The function frees the
dynamically allocated array object only if strmode & allocated != 0
and strmode & frozen == 0. (Subclause _lib.strstreambuf.virtuals_
describes how a dynamically allocated array object is freed.)
D.3.1.2 Member functions [depr.strstreambuf.members]
void freeze(bool freezefl = 1);
Effects:
If strmode & dynamic is non-zero, alters the freeze status of the
dynamic array object as follows:
--If freezefl is false, the function sets frozen in strmode.
--Otherwise, it clears frozen in strmode.
char* str();
Effects:
Calls freeze(), then returns the beginning pointer for the input
sequence, gbeg.
Notes:
The return value can be a null pointer.
int pcount() const;
Effects:
If the next pointer for the output sequence, pnext, is a null
pointer, returns zero. Otherwise, returns the current effective
length of the array object as the next pointer minus the beginning
pointer for the output sequence, pnext - pbeg.
D.3.1.3 strstreambuf overridden [depr.strstreambuf.virtuals]
virtual functions
int_type overflow(int_type c = ios_traits<char>::eof());
+------- BEGIN BOX 5 -------+
This needs to be rewritten in terms of consuming characters to be con
sistent with the revised protocol for overflow.
+------- END BOX 5 -------+
Effects:
Appends the character designated by c to the output sequence, if
possible, in one of two ways:
--If c != eof() and if either the output sequence has a write position
available or the function makes a write position available (as
described below), assigns c to *pnext++.
Returns (char)c.
--If c == eof(), there is no character to append.
Returns a value other than eof().
1 Returns eof() to indicate failure.
Notes:
The function can alter the number of write positions available as a
result of any call.
To make a write position available, the function reallocates (or
initially allocates) an array object with a sufficient number of
elements n to hold the current array object (if any), plus at least
one additional write position. How many additional write positions
are made available is otherwise unspecified.2) If palloc is not a
null pointer, the function calls (*palloc)(n) to allocate the new
dynamic array object. Otherwise, it evaluates the expression new
charT[n]. In either case, if the allocation fails, the function
returns eof(). Otherwise, it sets allocated in strmode.
2 To free a previously existing dynamic array object whose first element
address is p: If pfree is not a null pointer, the function calls
(*pfree)(p). Otherwise, it evaluates the expression delete[] p.
3 If strmode & dynamic == 0, or if strmode & frozen != 0, the function
cannot extend the array (reallocate it with greater length) to make a
write position available.
int_type pbackfail(int_type c = ios_traits<char>::eof());
+------- BEGIN BOX 6 -------+
This needs to be rewritten in terms of consuming characters to be con
sistent with the revised protocol for pbackfail.
+------- END BOX 6 -------+
4 Puts back the character designated by c to the input sequence, if pos
sible, in one of three ways:
--If c != eof(), if the input sequence has a putback position avail
able, and if (char)c == (char)gnext[-1], assigns gnext - 1 to gnext.
Returns (char)c.
_________________________
2) An implementation should consider alsize in making this decision.
--If c != eof(), if the input sequence has a putback position avail
able, and if strmode & constant is zero, assigns c to *--gnext.
Returns (char)c.
--If c == eof() and if the input sequence has a putback position
available, assigns gnext - 1 to gnext.
Returns (char)c.
5 Returns eof() to indicate failure.
Notes:
If the function can succeed in more than one of these ways, it is
unspecified which way is chosen. The function can alter the number
of putback positions available as a result of any call.
+------- BEGIN BOX 7 -------+
Cannot distinguish success and failure if c == EOF.
+------- END BOX 7 -------+
int_type underflow();
+------- BEGIN BOX 8 -------+
This needs to be rewritten in terms of consuming characters to be con
sistent with the revised protocol for underflow.
+------- END BOX 8 -------+
Effects:
Reads a character from the input sequence, if possible, without mov
ing the stream position past it, as follows:
--If the input sequence has a read position available the function
signals success by returning (char*)gnext.
--Otherwise, if the current write next pointer pnext is not a null
pointer and is greater than the current read end pointer gend, makes
a read position available by: assigning to gend a value greater than
gnext and no greater than pnext.
Returns (char)*gnext.
6 Returns eof() to indicate failure.
Notes:
The function can alter the number of read positions available as a
result of any call.
pos_type seekoff(off_type off, seekdir way, openmode which = in | out);
+------- BEGIN BOX 9 -------+
Check vs. _lib.stringbuf.virtuals_
+------- END BOX 9 -------+
Effects:
Alters the stream position within one of the controlled sequences,
if possible, as indicated in Table 5:
Table 5--seekoff positioning
+-----------------------------------------------------------------------+
| Conditions Result |
+-----------------------------------------------------------------------+
(which & ios::in) != 0 positions the input sequence |
+-----------------------------------------------------------------------+
(which & ios::out) != 0positions the output sequence |
+-----------------------------------------------------------------------+
|Otherwise, |
(which & (ios::in | positions both the input and the output sequences|
ios::out)) == (ios::in |
| ios::out)) |
|and way == either |
ios::beg or ios::end |
+-----------------------------------------------------------------------+
|Otherwise, the positioning operation fails. |
+-----------------------------------------------------------------------+
+------- BEGIN BOX 10 -------+
Comment: this condition is unclear. If the 2nd condition is true, is
the 1st condition always true? If so, the 2nd operation may occur,
mayn't it?
+------- END BOX 10 -------+
7 For a sequence to be positioned, if its next pointer is a null
pointer, the positioning operation fails. Otherwise, the function
determines newoff as indicated in Table 6:
Table 6--newoff values
+---------------------------------------------------------+
| Condition newoff Value |
+---------------------------------------------------------+
|way == ios::beg 0 |
+---------------------------------------------------------+
|way == ios::cur the next pointer minus the be |
| ginning pointer (xnext - xbeg) |
+---------------------------------------------------------+
|way == ios::end seekhigh minus the beginning |
| pointer (seekhigh - xbeg) |
+---------------------------------------------------------+
|If (newoff + off) < the positioning operation fails |
|(seeklow - xbeg), |
|or (seekhigh - xbeg) < |
|(newoff + off) |
+---------------------------------------------------------+
8 Otherwise, the function assigns xbeg + newoff + off to the next
pointer xnext.
Returns:
pos_type(newoff), constructed from the resultant offset newoff (of
type off_type), that stores the resultant stream position, if possi
ble. If the positioning operation fails, or if the constructed
object cannot represent the resultant stream position, the object
stores an invalid stream position.
+------- BEGIN BOX 11 -------+
Note: Need posT object which stores an invalid stream position. Com
ment: Not clear if the constructed object cannot represent the resul
tant stream position
+------- END BOX 11 -------+
pos_type seekpos(pos_type sp, ios_base::openmode which
= ios_base::in | ios_base::out);
Effects:
Alters the stream position within one of the controlled sequences,
if possible, to correspond to the stream position stored in sp (as
described below).
--If (which & ios::in) != 0, positions the input sequence.
--If (which & ios::out) != 0, positions the output sequence.
--If the function positions neither sequence, the positioning opera
tion fails.
9 For a sequence to be positioned, if its next pointer is a null
pointer, the positioning operation fails. Otherwise, the function
determines newoff from sp.offset():
--If newoff is an invalid stream position, has a negative value, or
has a value greater than (seekhigh - seeklow), the positioning oper
ation fails
--Otherwise, the function adds newoff to the beginning pointer xbeg
and stores the result in the next pointer xnext.
Returns:
pos_type(newoff), constructed from the resultant offset newoff (of
type off_type), that stores the resultant stream position, if possi
ble. If the positioning operation fails, or if the constructed
object cannot represent the resultant stream position, the object
stores an invalid stream position.
streambuf<char>* setbuf(char* s, streamsize n);
Effects:
Performs an operation that is defined separately for each class
derived from strstreambuf.
Default behavior:
the same as for streambuf::setbuf(char*, streamsize).
D.3.2 Template class istrstream [depr.istrstream]
namespace std {
class istrstream : public istream<char> {
public:
explicit istrstream(const char* s);
explicit istrstream(char* s);
istrstream(const char* s, streamsize n);
istrstream(char* s, streamsize n);
virtual ~istrstream();
strstreambuf* rdbuf() const;
char *str();
private:
// strstreambuf sb; exposition only
};
}
1 The class istrstream supports the reading of objects of class
strstreambuf. It supplies a strstreambuf object to control the asso
ciated array object. For the sake of exposition, the maintained data
is presented here as:
--sb, the strstreambuf object.
D.3.2.1 istrstream constructors [depr.istrstream.cons]
explicit istrstream(const char* s);
explicit istrstream(char* s);
Effects:
Constructs an object of class istrstream, initializing the base
class with istream(&sb) and initializing sb with strstreambuf(s,0)).
s shall designate the first element of an NTBS.
istrstream(const char* s, streamsize n);
Effects:
Constructs an object of class istrstream, initializing the base
class with istream(&sb) and initializing sb with strstreambuf(s,n)).
s shall designate the first element of an array whose length is n
elements, and n shall be greater than zero.
D.3.2.2 Member functions [depr.istrstream.members]
strstreambuf* rdbuf() const;
Returns:
(strstreambuf*)&sb.
char* str();
Returns:
rdbuf()->str().
D.3.3 Template class ostrstream [depr.ostrstream]
namespace std {
class ostrstream : public ostream<char> {
public:
ostrstream();
ostrstream(char* s, int n, ios_base::openmode mode = ios_base::out);
virtual ~ostrstream();
strstreambuf* rdbuf() const;
void freeze(int freezefl = 1);
char* str();
int pcount() const;
private:
// strstreambuf sb; exposition only
};
}
1 The class ostrstream supports the writing of objects of class
strstreambuf. It supplies a strstreambuf object to control the asso
ciated array object. For the sake of exposition, the maintained data
is presented here as:
--sb, the strstreambuf object.
D.3.3.1 ostrstream constructors [depr.ostrstream.cons]
ostrstream();
Effects:
Constructs an object of class ostrstream, initializing the base
class with ostream(&sb) and initializing sb with strstreambuf()).
ostrstream(char* s, int n, ios_base::openmode mode = ios_base::out);
Effects:
Constructs an object of class ostrstream, initializing the base
class with ostream(&sb), and initializing sb with one of two con
structors:
--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 + ::strlen(s)).3)
D.3.3.2 Member functions [depr.ostrstream.members]
strstreambuf* rdbuf() const;
Returns:
(strstreambuf*)&sb.
void freeze(int freezefl = 1);
Effects:
Calls rdbuf()->freeze(freezefl).
char* str();
Returns:
rdbuf()->str().
int pcount() const;
_________________________
3) The function signature strlen(const char*) is declared in <cstring>
(_lib.c.strings_).
Returns:
rdbuf()->pcount().