______________________________________________________________________

  18   Language support library         [lib.language.support]

  ______________________________________________________________________

1 This clause describes the function signatures that are called  implic­
  itly, and the types of objects generated implicitly, during the execu­
  tion of some C++ programs.  It also describes the headers that declare
  these function signatures and define any related types.

2 The   following  subclauses  describe  common  type  definitions  used
  throughout the library, characteristics of the predefined types, func­
  tions  supporting  start and termination of a C++ program, support for
  dynamic memory management, support for  dynamic  type  identification,
  support for exception processing, and other runtime support, as summa­
  rized in Table 1:

                Table 1--Language support library summary

     +--------------------------------------------------------------+
     |                   Subclause                       Header(s)  |
     +--------------------------------------------------------------+
     |_lib.support.types_ Types                         <cstddef>   |
     +--------------------------------------------------------------+
     |                                                  <limits>    |
     |_lib.support.limits_ Implementation properties    <climits>   |
     |                                                  <cfloat>    |
     +--------------------------------------------------------------+
     |_lib.support.start.term_ Start and termination    <cstdlib>   |
     +--------------------------------------------------------------+
     |_lib.support.dynamic_ Dynamic memory management   <new>       |
     +--------------------------------------------------------------+
     |_lib.support.rtti_ Type identification            <typeinfo>  |
     +--------------------------------------------------------------+
     |_lib.support.exception_ Exception handling        <exception> |
     +--------------------------------------------------------------+
     |                                                  <cstdarg>   |
     |                                                  <csetjmp>   |
     |_lib.support.runtime_ Other runtime support       <ctime>     |
     |                                                  <csignal>   |
     |                                                  <cstdlib>   |
     +--------------------------------------------------------------+

  18.1  Types                                        [lib.support.types]

1 Common definitons.

2 Header <cstddef> (Table 2):

                    Table 2--Header <cstddef> synopsis

                   +-----------------------------------+
                   | Kind             Name(s)          |
                   +-----------------------------------+
                   |Macros:   NULL        offsetof     |
                   +-----------------------------------+
                   |Types:    ptrdiff_t   size_t       |
                   +-----------------------------------+

3 The contents are the same as the Standard C library, with the  follow­
  ing changes:

4 The  macro NULL is an implementation-defined C++ null-pointer constant
  in this International Standard (_conv.ptr_).1)

5 The macro offsetof accepts a restricted set of type arguments in  this
  International  Standard.  type shall be a POD structure or a POD union
  (_class_).

  SEE ALSO: subclause _expr.sizeof_, Sizeof, subclause _expr.add_, Addi­
  tive  operators,  subclause   _class.free_, Free store, and ISO C sub­
  clause 7.1.6.

  18.2  Implementation properties                   [lib.support.limits]

1 Characteristics   of   implementation-dependent   fundamental    types
  (_basic.fundamental_).

  18.2.1  Numeric limits                                    [lib.limits]

1 The  numeric_limits  component provides a C++ program with information
  about various properties of the implementation's representation of the
  fundamental types.

2 Specializations  shall  be  provided  for  each fundamental type, both
  floating point and integer, including bool.  The member is_specialized
  shall be true for all such specializations of numeric_limits.

3 Non-fundamental  types,  such as complex<T> (_lib.complex_), shall not
  have specializations.

  _________________________
  1) Possible definitions include 0 and 0L, but not (void*)0.

4 A program may extend the namespace std by supplying template  special­
  izations for numeric_limits.

  Header <limits> synopsis

  namespace std {
    template<class T> class numeric_limits;
    enum float_round_style;

    class numeric_limits<bool>;

    class numeric_limits<char>;
    class numeric_limits<signed char>;
    class numeric_limits<unsigned char>;
    class numeric_limits<wchar_t>;

    class numeric_limits<short>;
    class numeric_limits<int>;
    class numeric_limits<long>;
    class numeric_limits<unsigned short>;
    class numeric_limits<unsigned int>;
    class numeric_limits<unsigned long>;

    class numeric_limits<float>;
    class numeric_limits<double>;
    class numeric_limits<long double>;
  }

  18.2.1.1  Template class numeric_limits           [lib.numeric.limits]
  namespace std {
    template<class T> class numeric_limits {
    public:
      static const bool is_specialized;
      static T min() throw;
      static T max() throw;
      static const int  digits;
      static const int  digits10;
      static const bool is_signed;
      static const bool is_integer;
      static const bool is_exact;
      static const int  radix;
      static T epsilon() throw;
      static T round_error() throw;

      static const int  min_exponent;
      static const int  min_exponent10;
      static const int  max_exponent;
      static const int  max_exponent10;

      static const bool has_infinity;
      static const bool has_quiet_NaN;
      static const bool has_signaling_NaN;
      static const bool has_denorm;
      static const bool has_denorm_loss;
      static T infinity() throw;
      static T quiet_NaN() throw;
      static T signaling_NaN() throw;
      static T denorm_min() throw;

      static const bool is_iec559;
      static const bool is_bounded;
      static const bool is_modulo;

      static const bool traps;
      static const bool tinyness_before;
      static const float_round_style round_style;
    };
  }

1 The  member  is_specialized  makes  it possible to distinguish between
  fundamental types, which have specializations, and  non-scalar  types,
  which do not.

2 The  members radix, epsilon(), and round_error() shall have meaningful
  values for all floating point type specializations.

3 For types with has_denorm ==  false,  the  member  denorm_min()  shall
  return the same value as the member min().

4 The  default  numeric_limits<T>  template  shall have all members, but
  with meaningless (0 or false) values.

  18.2.1.2  numeric_limits members          [lib.numeric.limits.members]

  static T min() throw;

1 Minimum finite value.2)

2 For floating types with denormalization, returns the minimum  positive
  normalized value, denorm_min().

  _________________________
  2) Equivalent to CHAR_MIN, SHRT_MIN, FLT_MIN, DBL_MIN, etc.

3 Meaningful  for  all  specializations  in which is_bounded == true, or
  is_bounded == false && is_signed == false.

  static T max() throw;

4 Maximum finite value.3)

5 Meaningful for all specializations in which is_bounded == true.

  static const int  digits;

6 Number of radix digits which can be represented without change.

7 For built-in integer types, the number of non-sign bits in the  repre­
  sentation.

8 For   floating  point  types,  the  number  of  radix  digits  in  the
  mantissa.4)

  static const int  digits10;

9 Number of base 10 digits which can be represented without change.5)

10Meaningful for all specializations in which is_bounded == true.

  static const bool is_signed;

11True if the type is signed.

12Meaningful for all specializations.

  static const bool is_integer;

13True if the type is integer.

14Meaningful for all specializations.

  _________________________
  3) Equivalent to CHAR_MAX, SHRT_MAX, FLT_MAX, DBL_MAX, etc.
  4) Equivalent to FLT_MANT_DIG, DBL_MANT_DIG, LDBL_MANT_DIG.
  5) Equivalent to FLT_DIG, DBL_DIG, LDBL_DIG.

  static const bool is_exact;

15True if the type uses an exact representation.  All integer types  are
  exact, but not all exact types are integer.  For example, rational and
  fixed-exponent representations are exact but not integer.

16Meaningful for all specializations.

  static const int  radix;

17For floating types, specifies the base or radix of the exponent repre­
  sentation (often 2).6)

18For integer types, specifies the base of the representation.7)

19Meaningful for all specializations.

  static T epsilon() throw;

20Machine epsilon:  the difference between 1 and the least value greater
  than 1 that is representable.8)

21Meaningful only for floating point types.

  static T round_error() throw;

22Measure of the maximum rounding error.9)

  static const int  min_exponent;

23Minimum  negative  integer  such that radix raised to that power is in
  range.10)

24Meaningful only for floating point types.

  _________________________
  6) Equivalent to FLT_RADIX.
  7) Distinguishes types with bases other than 2 (e.g. BCD).
  8) Equivalent to FLT_EPSILON, DBL_EPSILON, LDBL_EPSILON.
  9) This has a precise definition in the  Language  Independent  Arith­
  metic (LIA-1) standard.  Required by LIA-1.
  10) Equivalent to FLT_MIN_EXP, DBL_MIN_EXP, LDBL_MIN_EXP.

  static const int  min_exponent10;

25Minimum negative integer such that 10  raised  to  that  power  is  in
  range.11)

26Meaningful only for floating point types.

  static const int  max_exponent;

27Maximum  positive  integer  such that radix raised to that power is in
  range.12)

28Meaningful only for floating point types.

  static const int  max_exponent10;

29Maximum positive integer such that 10  raised  to  that  power  is  in
  range.13)

30Meaningful only for floating point types.

  static const bool has_infinity;

31True if the type has a representation for positive infinity.

32Meaningful only for floating point types.

33Shall be true for all specializations in which is_iec559 == true.

  static const bool has_quiet_NaN;

34True  if  the  type  has  a representation for a quiet (non-signaling)
  ``Not a Number.''14)

35Meaningful only for floating point types.

36Shall be true for all specializations in which is_iec559 == true.

  _________________________
  11) Equivalent to FLT_MIN_10_EXP, DBL_MIN_10_EXP, LDBL_MIN_10_EXP.
  12) Equivalent to FLT_MAX_EXP, DBL_MAX_EXP, LDBL_MAX_EXP.
  13) Equivalent to FLT_MAX_10_EXP, DBL_MAX_10_EXP, LDBL_MAX_10_EXP.
  14) Required by LIA-1.

  static const bool has_signaling_NaN;

37True if the  type  has  a  representation  for  a  signaling  ``Not  a
  Number.''15)

38Meaningful only for floating point types.

39Shall be true for all specializations in which is_iec559 == true.

  static const bool has_denorm;

40True  if the type allows denormalized values (variable number of expo­
  nent bits).16)

41Meaningful only for flotaing point types.

  static const bool has_denorm_loss;

42True if loss of accuracy is detected as a denormalization loss, rather
  than as an inexact result.17)

  static T infinity() throw;

43Representation of positive infinity, if available.18)

44Meaningful  only  in  specializations  for which has_infinity == true.
  Required in specializations for which is_iec559 == true.

  static T quiet_NaN() throw;

45Representation of a quiet ``Not a Number,'' if available.19)

46Meaningful only in specializations for which  has_quiet_NaN  ==  true.
  Required in specializations for which is_iec559 == true.

  _________________________
  15) Required by LIA-1.
  16) Required by LIA-1.
  17) See IEC 559.
  18) Required by LIA-1.
  19) Required by LIA-1.

  static T signaling_NaN() throw;

47Representation of a signaling ``Not a Number,'' if available.20)

48Meaningful  only  in  specializations  for  which has_signaling_NaN ==
  true.  Required in specializations for which is_iec559 == true.

  static T denorm_min() throw;

49Minimum positive denormalized value.21)

50Meaningful for all floating point types.

51In specializations for which has_denorm == false, returns the  minimum
  positive normalized value.

  static const bool is_iec559;

52True if and only if the type adheres to IEC 559 standard.22)

53Meaningful only for floating point types.

  static const bool is_bounded;

54True if the set of values representable by the type is finite.23)  All
  built-in  types  are bounded, this member would be false for arbitrary
  precision types.

55Meaningful for all specializations.

  static const bool is_modulo;

56True if the type is modulo.24) A type is modulo if it is  possible  to
  add  two  positive  numbers  and have a result which wraps around to a
  third number which is less.

  _________________________
  20) Required by LIA-1.
  21) Required by LIA-1.
  22) International Electrotechnical Commission standard 559 is the same
  as IEEE 754.
  23) Required by LIA-1.
  24) Required by LIA-1.

57Generally, this is false for floating types, true for  unsigned  inte­
  gers, and true for signed integers on most machines.

58Meaningful for all specializations.

  static const bool traps;

59true if trapping is implemented for the type.25)

60Meaningful for all specializations.

  static const bool tinyness_before;

61true if tinyness is detected before rounding.26)

62Meaningful only for floating point types.

  static const float_round_style round_style;

63The rounding style for the type.27)

64Meaningful  for all floating point types.  Specializations for integer
  types shall return round_toward_zero.

  18.2.1.3  Type float_round_style                     [lib.round.style]

  namespace std {
    enum float_round_style {
      round_indeterminate       = -1,
      round_toward_zero         =  0,
      round_to_nearest          =  1,
      round_toward_infinity     =  2,
      round_toward_neg_infinity =  3
    };
  }

  _________________________
  25) Required by LIA-1.
  26) Refer to IEC 559.  Required by LIA-1.
  27) Equivalent to FLT_ROUNDS.  Required by LIA-1.

  18.2.1.4  numeric_limits specializations         [lib.numeric.special]

1 All members shall be provided for all specializations.  However,  many
  values  are  only  required  to be meaningful under certain conditions
  (for example, epsilon() is only meaningful if  is_integer  is  false).
  Any value which is not ``meaningful'' shall be set to 0 or false.

2 [Example:
  namespace std {
    class numeric_limits<float> {
    public:
      static const bool is_specialized = true;
      inline static float min() { return 1.17549435E-38F; }
      inline static float max() { return 3.40282347E+38F; }
      static const int digits   = 24;
      static const int digits10 =  6;
      static const bool is_signed  = true;
      static const bool is_integer = false;
      static const bool is_exact   = false;
      static const int radix = 2;
      inline static float epsilon()     { return 1.19209290E-07F; }
      inline static float round_error() { return 0.5F; }
      static const int min_exponent   = -125;
      static const int min_exponent10 = - 37;
      static const int max_exponent   = +128;
      static const int max_exponent10 = + 38;
      static const bool has_infinity      = true;
      static const bool has_quiet_NaN     = true;
      static const bool has_signaling_NaN = true;
      static const bool has_denorm        = false;
      static const bool has_denorm_loss   = false;
      inline static float infinity()      { return ...; }
      inline static float quiet_NaN()     { return ...; }
      inline static float signaling_NaN() { return ...; }
      inline static float denorm_min()    { return min(); }
      static const bool is_iec559  = true;
      static const bool is_bounded = true;
      static const bool is_modulo  = false;
      static const bool traps      = true;
      static const bool tinyness_before = true;
      static const float_round_style round_style = round_to_nearest;
    };
  }
   --end example]

  18.2.2  C Library                                       [lib.c.limits]

1 Header <climits> (Table 3):

                    Table 3--Header <climits> synopsis

  +---------------------------------------------------------------------+
  |  Type                              Name(s)                          |
  +---------------------------------------------------------------------+
  |Values:                                                              |
  |CHAR_BIT   INT_MAX    LONG_MIN     SCHAR_MIN   UCHAR_MAX   USHRT_MAX |
  |CHAR_MAX   INT_MIN    MB_LEN_MAX   SHRT_MAX    UINT_MAX              |
  |CHAR_MIN   LONG_MAX   SCHAR_MAX    SHRT_MIN    ULONG_MAX             |
  +---------------------------------------------------------------------+

2 The contents are the same as the Standard C library.

3 Header <cfloat> (Table 4):

                    Table 4--Header <cfloat> synopsis

   +-------------------------------------------------------------------+
   |     Type                             Name(s)                      |
   +-------------------------------------------------------------------+
   |Values:                                                            |
   |DBL_DIG          DBL_MIN_EXP      FLT_MIN_10_EXP   LDBL_MAX_10_EXP |
   |DBL_EPSILON      FLT_DIG          FLT_MIN_EXP      LDBL_MAX_EXP    |
   |DBL_MANT_DIG     FLT_EPSILON      FLT_RADIX        LDBL_MIN        |
   |DBL_MAX          FLT_MANT_DIG     FLT_ROUNDS       LDBL_MIN_10_EXP |
   |DBL_MAX_10_EXP   FLT_MAX          LDBL_DIG         LDBL_MIN_EXP    |
   |DBL_MAX_EXP      FLT_MAX_10_EXP   LDBL_EPSILON                     |
   |DBL_MIN          FLT_MAX_EXP      LDBL_MANT_DIG                    |
   |DBL_MIN_10_EXP   FLT_MIN          LDBL_MAX                         |
   +-------------------------------------------------------------------+

4 The contents are the same as the Standard C library.

  SEE ALSO: ISO C subclause 7.1.5, 5.2.4.2.2, 5.2.4.2.1.

  18.3  Start and termination                   [lib.support.start.term]

1 Header <cstdlib> (partial), Table 5:

                    Table 5--Header <cstdlib> synopsis

               +-------------------------------------------+
               |   Type                 Name(s)            |
               +-------------------------------------------+
               |Macros:      EXIT_FAILURE     EXIT_SUCCESS |
               +-------------------------------------------+
               |Functions:   abort   atexit   exit         |
               +-------------------------------------------+

2 The  contents are the same as the Standard C library, with the follow­
  ing changes:

  atexit(void (*f)(void))

3 The function atexit(), has additional behavior in  this  International
  Standard:

  --For  the  execution of a function registered with atexit, if control
    leaves the function because it provides  no  handler  for  a  thrown
    exception, terminate() is called (_lib.terminate_).

  exit(int status)

4 The  function  exit()  has  additional  behavior in this International
  Standard:

  --First, all functions f registered by calling atexit(f)  are  called,
    in the reverse order of their registration.28)

  --Next, all static objects are destroyed in the reverse order of their
    construction.   (Automatic  objects are not destroyed as a result of
    calling exit().)29)

  --Next,  all  open  C  streams (as mediated by the function signatures
    declared in <cstdio>) with unwritten buffered data are flushed,  all
    open  C  streams  are  closed, and all files created by calling tmp­
    file() are removed.30)
  _________________________
  28)  A  function is called for every time it is registered.  The func­
  tion signature atexit(void (*)()), is declared in <cstdlib>.
  29) Automatic objects are all destroyed in a  program  whose  function
  main()  contains no automatic objects and executes the call to exit().
  Control can be transferred directly to such a main()  by  throwing  an
  exception that is caught in main().
  30)   Any   C    streams    associated    with    cin,    cout,    etc

  --Finally,  control is returned to the host environment.  If status is
    zero or EXIT_SUCCESS, an implementation-defined form of  the  status
    successful  termination  is returned.  If status is EXIT_FAILURE, an
    implementation-defined form of the status  unsuccessful  termination
    is     returned.      Otherwise     the     status    returned    is
    implementation-defined.31)

5 The function exit() never returns to its caller.

  SEE ALSO:  subclauses  _basic.start_,  _basic.start.term_,  ISO C sub­
  clause 7.10.4.

  18.4  Dynamic memory management                  [lib.support.dynamic]

1 The header <new> defines several functions that manage the  allocation
  of  dynamic  storage  in  a  program.   It also defines components for
  reporting storage management errors.

  Header <new> synopsis

  #include <cstdlib>      // for size_t
  #include <exception>    // for exception
  namespace std {
    class bad_alloc;
    struct nothrow {};
    typedef void (*new_handler)();
    new_handler set_new_handler(new_handler new_p) throw();
  }
    void* operator new(size_t size) throw(std::bad_alloc);
    void* operator new(size_t size, const std::nothrow&) throw();
    void  operator delete(void* ptr) throw();
    void  operator delete(void* ptr, const std::nothrow&) throw();
    void* operator new[](size_t size) throw(std::bad_alloc);
    void* operator new[](size_t size, const std::nothrow&) throw();
    void  operator delete[](void* ptr) throw();
    void  operator delete[](void* ptr, const std::nothrow&) throw();
    void* operator new  (size_t size, void* ptr) throw();
    void* operator new[](size_t size, void* ptr) throw();
    void  operator delete  (void* ptr, void*) throw();
    void  operator delete[](void* ptr, void*) throw();

  SEE ALSO: subclauses _intro.memory_, _basic.stc.dynamic_,  _expr.new_,
  _expr.delete_, _class.free_, subclause _lib.memory_, Memory.

  +-------                 BEGIN BOX 1                -------+
  The  division  of labor between the global namespace and namespace std
  should probably be reexamined, as should making nothrow a type instead
  _________________________
  (_lib.iostream.objects_)  are  flushed  and closed when static objects
  are destroyed in the previous phase.  The function  tmpfile()  is  de­
  clared in <cstdio>.
  31) The macros EXIT_FAILURE and EXIT_SUCCESS are defined in <cstdlib>.

  of a value.  ARK 9/95
  +-------                  END BOX 1                 -------+

  18.4.1  Storage allocation and deallocation           [lib.new.delete]

  18.4.1.1  Single-object forms                  [lib.new.delete.single]

  void* operator new(size_t size) throw(bad_alloc);

  Effects:
    The allocation function (_basic.stc.dynamic.allocation_) called by a
    new-expression (_expr.new_) to allocate size bytes of storage  suit­
    ably aligned to represent any object of that size.
  Replaceable:
    a  C++  program  may  define a function with this function signature
    that displaces the default  version  defined  by  the  C++  Standard
    library.
  Required behavior:
    Return     a    pointer    to    dynamically    allocated    storage
    (_basic.stc.dynamic_), or else throw a bad_alloc exception.
  Default behavior:

  --Executes a loop: Within the loop, the  function  first  attempts  to
    allocate the requested storage.  Whether the attempt involves a call
    to the Standard C library function malloc is unspecified.

  --Returns a pointer to the allocated storage if the  attempt  is  suc­
    cessful.  Otherwise, if the last argument to set_new_handler() was a
    null pointer, throw bad_alloc.

  --Otherwise,   the   function   calls    the    current    new_handler
    (_lib.new.handler_).   If  the  called  function  returns,  the loop
    repeats.

  --The loop terminates when an attempt to allocate the requested  stor­
    age  is  successful  or  when a called new_handler function does not
    return.

  void* operator new(size_t size, const nothrow&) throw();

  Effects:
    Same as above, except that it is called by a placement version of  a
    new-expression  when  a C++ program prefers a null pointer result as
    an error indication, instead of a bad_alloc exception.
  Replaceable:
    a C++ program may define a function  with  this  function  signature
    that  displaces  the  default  version  defined  by the C++ Standard
    library.
  Required behavior:
    Return    a    pointer    to    dynamically    allocated     storage

    (_basic.stc.dynamic_),  or else return a null pointer.  This nothrow
    version of operator new returns a pointer obtained  as  if  acquired
    from  the  ordinary  version.   This  requirement  is  binding  on a
    replacement version of this function.
  Default behavior:

  --Executes a loop: Within the loop, the  function  first  attempts  to
    allocate the requested storage.  Whether the attempt involves a call
    to the Standard C library function malloc is unspecified.

  --Returns a pointer to the allocated storage if the  attempt  is  suc­
    cessful.  Otherwise, if the last argument to set_new_handler() was a
    null pointer, return a null pointer.

  --Otherwise,   the   function   calls    the    current    new_handler
    (_lib.new.handler_).   If  the  called  function  returns,  the loop
    repeats.

  --The loop terminates when an attempt to allocate the requested  stor­
    age  is  successful  or  when a called new_handler function does not
    return.  If the called new_handler function terminates by throwing a
    bad_alloc exception, the function returns a null pointer.

1 [Example:
  T* p1 = new T;             // throws bad_alloc if it fails
  T* p2 = new(nothrow()) T;  // returns 0 if it fails
   --end example]

  void operator delete(void* ptr) throw();
  void  operator delete(void* ptr, const std::nothrow&) throw();

  Effects:
    The  deallocation function (_basic.stc.dynamic.deallocation_) called
    by a delete-expression to render the value of ptr invalid.
  Replaceable:
    a C++ program may define a function  with  this  function  signature
    that  displaces  the  default  version  defined  by the C++ Standard
    library.
  Required behavior:
    accept a value of ptr that is null or that was returned by  an  ear­
    lier   call   to   the  default  operator  new(size_t)  or  operator
    new(size_t,const nothrow&).
  Default behavior:

  --For a null value of ptr, do nothing.

  --Any other value of ptr shall be a value returned earlier by  a  call
    to the default operator new.32) For such a non-null  value  of  ptr,
  _________________________
  32) The value must not have been invalidated by an intervening call to
  operator delete(void*) (_lib.res.on.arguments_).

    reclaims storage allocated by the earlier call to the default opera­
    tor new.
  Notes:
    It is  unspecified  under  what  conditions  part  or  all  of  such
    reclaimed  storage is allocated by a subsequent call to operator new
    or any of calloc, malloc, or realloc, declared in <cstdlib>.

  18.4.1.2  Array forms                           [lib.new.delete.array]

  void* operator new[](size_t size) throw(bad_alloc);

  Effects:
    The allocation function (_basic.stc.dynamic.allocation_)  called  by
    the  array  form  of  a new-expression (_expr.new_) to allocate size
    bytes of storage suitably aligned to represent any array  object  of
    that size or smaller.33)
  Replaceable:
    a C++ program can define a function  with  this  function  signature
    that  displaces  the  default  version  defined  by the C++ Standard
    library.
  Required behavior:
    Same as for operator new(size_t).  This nothrow version of  operator
    new[]  returns  a  pointer obtained as if acquired from the ordinary
    version.  This requirement is binding on a  replacement  version  of
    this function.
  Default behavior:
    Returns operator new(size).

  void* operator new[](size_t size, const nothrow&) throw();

  Effects:
    Same  as above, except that it is called by a placement version of a
    new-expression when a C++ program prefers a null pointer  result  as
    an error indication, instead of a bad_alloc exception.
  Replaceable:
    a  C++  program  can  define a function with this function signature
    that displaces the default  version  defined  by  the  C++  Standard
    library.
  Required behavior:
    Same as for operator new(size_t,const nothrow&).
  Default behavior:
    Returns operator new(size,nothrow()).

  _________________________
  33)  It  is not the direct responsibility of operator new[](size_t) or
  operator delete[](void*) to note the repetition count or element  size
  of  the  array.  Those operations are performed elsewhere in the array
  new and delete expressions.  The array new expression,  may,  however,
  increase  the  size argument to operator new[](size_t) to obtain space
  to store supplemental information.

  void operator delete[](void* ptr) throw();
  void  operator delete[](void* ptr, const std::nothrow&) throw();

  +-------                 BEGIN BOX 2                -------+
  The array form void  operator delete[](void* ptr, const std::nothrow&)
  throw(); was added during editing to correct  an  oversight  in  issue
  18-014.  BGD 1/96
  +-------                  END BOX 2                 -------+

  Effects:
    The  deallocation function (_basic.stc.dynamic.deallocation_) called
    by the array form of a delete-expression to render the value of  ptr
    invalid.
  Replaceable:
    a  C++  program  can  define a function with this function signature
    that displaces the default  version  defined  by  the  C++  Standard
    library.
  Required behavior:
    accept  a  value of ptr that is null or that was returned by an ear­
    lier call to operator new[](size_t) or  operator  new[](size_t,const
    std::nothrow&).
  Default behavior:

  --For a null value of ptr, does nothing.

  --Any  other  value of ptr shall be a value returned earlier by a call
    to  the default operator new[](size_t).34) For such a non-null value
    of ptr, reclaims storage  allocated  by  the  earlier  call  to  the
    default operator new[].

1 It  is unspecified under what conditions part or all of such reclaimed
  storage is allocated by a subsequent call to operator new  or  any  of
  calloc, malloc, or realloc, declared in <cstdlib>.

  18.4.1.3  Placement forms                   [lib.new.delete.placement]

1 These  functions  are reserved, a C++ program may not define functions
  that   displace   the   versions   in   the   Standard   C++   library
  (_lib.constraints_).

  void* operator new(size_t size, void* ptr) throw();

  Returns:
    ptr.
  Notes:
    Intentionally performs no other action.

  _________________________
  34) The value must not have been invalidated by an intervening call to
  operator delete[](void*) (_lib.res.on.arguments_).

2 [Example:  This  can  be  useful for constructing an object at a known
  address:
  char place[sizeof(Something)];
  Something* p = new (place) Something();
   --end example]

  void* operator new[](size_t size, void* ptr) throw();

  Returns:
    ptr.
  Notes:
    Intentionally performs no other action.

  void operator delete(void* ptr, void*) throw();

  Effects:
    Intentionally performs no action.
  Notes:
    Default function called for a placement delete expression.   Comple­
    ments default placement new.

  void operator delete[](void* ptr, void*) throw();

  Effects:
    Intentionally performs no action.
  Notes:
    Default  function  called  for  a placement array delete expression.
    Complements default placement new[].

  18.4.2  Storage allocation errors                   [lib.alloc.errors]

  18.4.2.1  Class bad_alloc                              [lib.bad.alloc]
  namespace std {
    class bad_alloc : public exception {
    public:
      bad_alloc() throw();
      bad_alloc(const bad_alloc&) throw();
      bad_alloc& operator=(const bad_alloc&) throw();
      virtual ~bad_alloc() throw();
      virtual const char* what() const throw();
    };
  }

1 The class bad_alloc defines the type of objects thrown  as  exceptions
  by the implementation to report a failure to allocate storage.

  bad_alloc() throw();

  Effects:
    Constructs an object of class bad_alloc.

      bad_alloc(const bad_alloc&) throw();
      bad_alloc& operator=(const bad_alloc&) throw();

  Effects:
    Copies an object of class bad_alloc.
  Notes:
    The  result  of  calling  what()  on the newly constructed object is
    implementation-defined.

  virtual const char* what() const throw();

  Returns:
    An implementation-defined value.

  18.4.2.2  Type new_handler                           [lib.new.handler]

  typedef void (*new_handler)();

1 The type of a handler function to be called by operator new() or oper­
  ator new[]() (_lib.new.delete_) when they cannot satisfy a request for
  addtional storage.
  Required behavior:
    A new_handler shall perform one of the following:

  --make more storage available for allocation and then return;

  --throw an exception  of  type  bad_alloc  or  a  class  derived  from
    bad_alloc;

  --call either abort() or exit();
  Default behavior:
    The implementation's default new_handler throws an exception of type
    bad_alloc.

  18.4.2.3  set_new_handler                        [lib.set.new.handler]

  new_handler set_new_handler(new_handler new_p) throw();

  Effects:
    Establishes  the  function  designated  by  new_p  as  the   current
    new_handler.
  Returns:
    the previous new_handler.

  18.5  Type identification                           [lib.support.rtti]

1 The  header <typeinfo> defines a type associated with type information
  generated by the  implementation.   It  also  defines  two  types  for
  reporting dynamic type identification errors.

  Header <typeinfo> synopsis

  #include <exception>    // for exception

  namespace std {
    class type_info;
    class bad_cast;
    class bad_typeid;
  }

  SEE ALSO: subclauses _expr.dynamic.cast_, _expr.typeid_.

  18.5.1  Class type_info                                [lib.type.info]
  namespace std {
    class type_info {
    public:
      virtual ~type_info();
      bool operator==(const type_info& rhs) const;
      bool operator!=(const type_info& rhs) const;
      bool before(const type_info& rhs) const;
      const char* name() const;
    private:
      type_info(const type_info& rhs);
      type_info& operator=(const type_info& rhs);
    };
  }

1 The class type_info describes type information generated by the imple­
  mentation.  Objects of this class effectively store  a  pointer  to  a
  name  for  the  type,  and an encoded value suitable for comparing two
  types for equality or collating order.  The names, encoding rule,  and
  collating  sequence  for  types  are  all  unspecified  and may differ
  between programs.

  bool operator==(const type_info& rhs) const;

  Effects:
    Compares the current object with rhs.
  Returns:
    true if the two values describe the same type.

  bool operator!=(const type_info& rhs) const;

  Returns:
    !(*this == rhs).

  bool before(const type_info& rhs) const;

  Effects:
    Compares the current object with rhs.
  Returns:
    true if *this precedes rhs in the implementation's collation  order.

  const char* name() const;

  Returns:
    an implementation-defined value.
  Notes:
    The    message   may   be   a   null-terminated   multibyte   string
    (_lib.multibyte.strings_), suitable for conversion and display as  a
    wstring (_lib.wstring_, _lib.locale.codecvt_)

  type_info(const type_info& rhs);
  type_info& operator=(const type_info& rhs);

  Effects:
    Copies a type_info object.
  Notes:
    Since the copy constructor and assignment operator for type_info are
    private to the class, objects of this type cannot be copied.

  18.5.2  Class bad_cast                                  [lib.bad.cast]
  namespace std {
    class bad_cast : public exception {
    public:
      bad_cast() throw();
      bad_cast(const bad_cast&) throw();
      bad_cast& operator=(const bad_cast&) throw();
      virtual ~bad_cast() throw();
      virtual const char* what() const throw();
    };
  }

1 The class bad_cast defines the type of objects thrown as exceptions by
  the  implementation to report the execution of an invalid dynamic-cast
  expression (_expr.dynamic.cast_).

  bad_cast() throw();

  Effects:
    Constructs an object of class bad_cast.

      bad_cast(const bad_cast&) throw();
      bad_cast& operator=(const bad_cast&) throw();

  Effects:
    Copies an object of class bad_cast.
  Notes:
    The result of calling what() on  the  newly  constructed  object  is
    implementation-defined.

  virtual const char* what() const throw();

  Returns:
    An implementation-defined value.
  Notes:
    The    message   may   be   a   null-terminated   multibyte   string
    (_lib.multibyte.strings_), suitable for conversion and display as  a
    wstring (_lib.wstring_, _lib.locale.codecvt_)

  18.5.3  Class bad_typeid                              [lib.bad.typeid]
  namespace std {
    class bad_typeid : public exception {
    public:
      bad_typeid() throw();
      bad_typeid(const bad_typeid&) throw();
      bad_typeid& operator=(const bad_typeid&) throw();
      virtual ~bad_typeid() throw();
      virtual const char* what() const throw();
    };
  }

1 The  class bad_typeid defines the type of objects thrown as exceptions
  by the implementation to report a null pointer in a typeid  expression
  (_expr.typeid_).

  bad_typeid() throw();

  Effects:
    Constructs an object of class bad_typeid.

      bad_typeid(const bad_typeid&) throw();
      bad_typeid& operator=(const bad_typeid&) throw();

  Effects:
    Copies an object of class bad_typeid.
  Notes:
    The  result  of  calling  what()  on the newly constructed object is
    implementation-defined.

  virtual const char* what() const throw();

  Returns:
    An implementation-defined value.

  Notes:
    The   message   may   be   a   null-terminated   multibyte    string
    (_lib.multibyte.strings_),  suitable for conversion and display as a
    wstring (_lib.wstring_, _lib.locale.codecvt_)

  18.6  Exception handling                       [lib.support.exception]

1 The header <exception> defines several types and functions related  to
  the handling of exceptions in a C++ program.

  Header <exception> synopsis

  namespace std {
    class exception;
    class bad_exception;
    typedef void (*unexpected_handler)();
    unexpected_handler set_unexpected(unexpected_handler f) throw();
    void unexpected();
    typedef void (*terminate_handler)();
    terminate_handler set_terminate(terminate_handler f) throw();
    void terminate();
  }

  SEE ALSO: subclause _except.special_.

  18.6.1  Class exception                                [lib.exception]
  namespace std {
    class exception {
    public:
      exception() throw();
      exception(const exception&) throw();
      exception& operator=(const exception&) throw();
      virtual ~exception() throw();
      virtual const char* what() const throw();
    };
  }

1 The  class  exception  defines the base class for the types of objects
  thrown as exceptions by C++ Standard library components,  and  certain
  expressions, to report errors detected during program execution.

  exception() throw();

  Effects:
    Constructs an object of class exception.
  Notes:
    Does not throw any exceptions.

  exception(const exception&) throw();
  exception& operator=(const exception&) throw();

  Effects:
    Copies an exception object.
  Notes:
    The  effects  of calling what() after assignment are implementation-
    defined.

  virtual ~exception() throw();

  Effects:
    Destroys an object of class exception.
  Notes:
    Does not throw any exceptions.

  virtual const char* what() const throw();

  Returns:
    An implementation-defined NTBS.
  Notes:
    The   message   may   be   a   null-terminated   multibyte    string
    (_lib.multibyte.strings_),  suitable for conversion and display as a
    wstring (_lib.wstring_, _lib.locale.codecvt_)

  18.6.2  Violating exception-                [lib.exception.unexpected]
       specifications

  18.6.2.1  Class bad_exception                      [lib.bad.exception]
  namespace std {
    class bad_exception : public exception {
    public:
      bad_exception() throw();
      bad_exception(const bad_exception&) throw();
      bad_exception& operator=(const bad_exception&) throw();
      virtual ~bad_exception() throw();
      virtual const char* what() const throw();
    };
  }

1 The  class  bad_exception  defines  the  type  of  objects  thrown  as
  described in (_except.unexpected_).

  bad_exception() throw();

  Effects:
    Constructs an object of class bad_exception.

      bad_exception(const bad_exception&) throw();
      bad_exception& operator=(const bad_exception&) throw();

  Effects:
    Copies an object of class bad_exception.
  Notes:
    The result of calling what() on  the  newly  constructed  object  is
    implementation-defined.

  virtual const char* what() const throw();

  Returns:
    An implementation-defined value.
  Notes:
    The    message   may   be   a   null-terminated   multibyte   string
    (_lib.multibyte.strings_), suitable for conversion and display as  a
    wstring (_lib.wstring_, _lib.locale.codecvt_)

  18.6.2.2  Type unexpected_handler             [lib.unexpected.handler]

  typedef void (*unexpected_handler)();

1 The  type  of  a  handler function to be called by unexpected() when a
  function attempts to throw an exception not listed in  its  exception-
  specification.
  Required behavior:
    an  unexpected_handler  shall either throw an exception or terminate
    execution of the program without returning to the caller.  An  unex­
    pected_handler may perform any of the following:

  --throw an exception that satisfies the exception specification;

  --throw a bad_exception exception;

  --call terminate();

  --call either abort() or exit();
  Default behavior:
    The implementation's default unexpected_handler calls terminate().

  18.6.2.3  set_unexpected                          [lib.set.unexpected]

  unexpected_handler set_unexpected(unexpected_handler f) throw();

  Effects:
    Establishes  the  function  designated  by  f  as  the current unex­
    pected_handler.
  Requires:
    f shall not be a null pointer.
  Returns:
    The previous unexpected_handler.

  18.6.2.4  unexpected                                  [lib.unexpected]

  void unexpected();

1 Called by the  implementation  when  a  function  with  an  exception-
  specification throws an exception that is not listed in the exception-
  specification (_except.unexpected_).
  Effects:
    Calls    the    current    unexpected_handler    handler    function
    (_lib.unexpected.handler_).

  18.6.3  Abnormal termination                 [lib.exception.terminate]

  18.6.3.1  Type terminate_handler               [lib.terminate.handler]

  typedef void (*terminate_handler)();

1 The type of a handler function to be called by terminate() when termi­
  nating exception processing.
  Required behavior:
    A terminate_handler shall terminate execution of the program without
    returning to the caller.
  Default behavior:
    The implementation's default terminate_handler calls abort().

  18.6.3.2  set_terminate                            [lib.set.terminate]

  terminate_handler set_terminate(terminate_handler f) throw();

  Effects:
    Establishes  the  function  designated  by  f as the current handler
    function for terminating exception processing.
  Requires:
    f shall not be a null pointer.
  Returns:
    The previous terminate_handler.

  18.6.3.3  terminate                                    [lib.terminate]

  void terminate();

1 Called by the implementation when exception handling must be abandoned
  for any of several reasons (_except.terminate_).
  Effects:
    Calls     the    current    terminate_handler    handler    function
    (_lib.terminate.handler_).

  18.6.4  uncaught_exception                              [lib.uncaught]

  bool uncaught_exception();

  Returns:
    true after completing evaluation of the object to  be  thrown  until
    completing  the  initialization  of the exception-declaration in the
    matching handler (_except.uncaught_).
  Notes:
    When uncaught_exception() is true, throwing an exception can  result
    in a call of terminate (_except.terminate_).

  18.7  Other runtime support                      [lib.support.runtime]

1 Headers  <cstdarg>  (variable  arguments), <csetjmp> (nonlocal jumps),
  <ctime> (system clock clock(), time()), <csignal>  (signal  handling),
  and <cstdlib> (runtime environment getenv(), system()).

                    Table 6--Header <cstdarg> synopsis

                 +--------------------------------------+
                 | Type               Name(s)           |
                 +--------------------------------------+
                 |Macros:   va_arg    va_end   va_start |
                 +--------------------------------------+
                 |Type:     va_list                     |
                 +--------------------------------------+

                    Table 7--Header <csetjmp> synopsis

                          +--------------------+
                          |  Type      Name(s) |
                          +--------------------+
                          |Macro:      setjmp  |
                          +--------------------+
                          |Type:       jmp_buf |
                          +--------------------+
                          |Function:   longjmp |
                          +--------------------+

                     Table 8--Header <ctime> synopsis

                      +----------------------------+
                      |   Type         Name(s)     |
                      +----------------------------+
                      |Macros:      CLOCKS_PER_SEC |
                      +----------------------------+
                      |Types:       clock_t        |
                      +----------------------------+
                      |Functions:   clock          |
                      +----------------------------+

                    Table 9--Header <csignal> synopsis

         +-------------------------------------------------------+
         |   Type                       Name(s)                  |
         +-------------------------------------------------------+
         |Macros:      SIGABRT        SIGILL   SIGSEGV   SIG_DFL |
         |SIG_IGN      SIGFPE         SIGINT   SIGTERM   SIG_ERR |
         +-------------------------------------------------------+
         |Type:        sig_atomic_t                              |
         +-------------------------------------------------------+
         |Functions:   raise          signal                     |
         +-------------------------------------------------------+

                   Table 10--Header <cstdlib> synopsis

                      +-----------------------------+
                      |   Type          Name(s)     |
                      +-----------------------------+
                      |Functions:   getenv   system |
                      +-----------------------------+

2 The  contents are the same as the Standard C library, with the follow­
  ing changes:

3 The restrictions that ISO C places on  the  second  parameter  to  the
  va_start()  macro  in header <stdarg.h> are different in this Interna­
  tional Standard.  The parameter parmN is the identifier of the  right­
  most  parameter in the variable parameter list of the function defini­
  tion (the one just  before  the  ...).   If  the  parameter  parmN  is
  declared  with  a  function,  array, or reference type, or with a type
  that is not compatible with the type  that  results  when  passing  an
  argument for which there is no parameter, the behavior is undefined.

  SEE ALSO: ISO C subclause 4.8.1.1.

4 The  function  signature  longjmp(jmp_buf  jbuf,  int  val)  has  more
  restricted behavior in this International Standard.  If any  automatic
  objects  would be destroyed by a thrown exception transferring control
  to another  (destination)  point  in  the  program,  then  a  call  to
  longjmp(jbuf,  val)  at  the throw point that transfers control to the
  same (destination) point has undefined behavior.

  SEE ALSO: ISO C subclause 7.10.4, 7.8, 7.6, 7.12.