______________________________________________________________________

  Annex D (normative)

  Compatibility features                                [depr]

  ______________________________________________________________________

1 This Clause describes features of the C++ Standard that are  specified
  for compatibility with existing implementations.

  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]

  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_.

  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
    };
  }

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.

  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_
  _________________________
  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_).

    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());

  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());

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.

  --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.

  int_type underflow();

  _________________________
  2) An implementation should consider alsize in making this decision.

  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);

  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.                 |
  +-----------------------------------------------------------------------+

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.

  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

    operation 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;

  Returns:
    rdbuf()->pcount().

  _________________________
  3) The function signature strlen(const char*) is declared in <cstring>
  (_lib.c.strings_).