______________________________________________________________________

  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 definitions.

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 header <stddef.h>,
  with the following 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
  (clause _class_).  The result of applying  the  offsetof  macro  to  a
  field  that is a static data member or a function member is undefined.

  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 The headers <limits>, <climits>, and <cfloat>  supply  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 For  all members declared static const in the numeric_limits template,
  specializations shall define these values in such a way that they  are
  usable as integral constant expressions.
  _________________________
  1) Possible definitions include 0 and 0L, but not (void*)0.

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

  Header <limits> synopsis

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

    template<> class numeric_limits<bool>;

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

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

    template<> class numeric_limits<float>;
    template<> class numeric_limits<double>;
    template<> 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 = false;
      static T min() throw();
      static T max() throw();
      static const int  digits = 0;
      static const int  digits10 = 0;
      static const bool is_signed = false;
      static const bool is_integer = false;
      static const bool is_exact = false;
      static const int  radix = 0;
      static T epsilon() throw();
      static T round_error() throw();

      static const int  min_exponent = 0;
      static const int  min_exponent10 = 0;
      static const int  max_exponent = 0;
      static const int  max_exponent10 = 0;

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

      static const bool is_iec559 = false;
      static const bool is_bounded = false;
      static const bool is_modulo = false;

      static const bool traps = false;
      static const bool tinyness_before = false;
      static const float_round_style round_style = round_toward_zero;
    };
  }

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 default numeric_limits<T> template shall  have  all  members,  but
  with 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.

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

  static T max() throw();

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

4 Maximum finite value.3)

5 Meaningful for all specializations in which is_bounded != false.

  static const int  digits;

6 Number of radix digits that 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 that can be represented without change.5)

10Meaningful for all specializations in which is_bounded != false.

  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.

  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.

  _________________________
  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.

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 for all 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 the power of one
  less than that integer is a normalized floating point number.10)

24Meaningful for all floating point types.

  static const int  min_exponent10;

25Minimum negative integer such that 10 raised to that power is  in  the
  range of normalized floating point numbers.11)
  _________________________
  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) Rounding error is described in ISO/IEC 10967-1 Language independent
  arithmetic - Part 1  Section  5.2.8  and  Annex  A  Rationale  Section
  A.5.2.8 - Rounding constants.
  10) Equivalent to FLT_MIN_EXP, DBL_MIN_EXP, LDBL_MIN_EXP.
  11) Equivalent to FLT_MIN_10_EXP, DBL_MIN_10_EXP, LDBL_MIN_10_EXP.

26Meaningful for all floating point types.

  static const int  max_exponent;

27Maximum  positive integer such that radix raised to the power one less
  than that integer is a representable finite floating point number.12)

28Meaningful for all floating point types.

  static const int  max_exponent10;

29Maximum positive integer such that 10 raised to that power is  in  the
  range of representable finite floating point numbers.13)

30Meaningful for all floating point types.

  static const bool has_infinity;

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

32Meaningful for all floating point types.

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

  static const bool has_quiet_NaN;

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

35Meaningful for all floating point types.

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

  static const bool has_signaling_NaN;

37True if the  type  has  a  representation  for  a  signaling  ``Not  a
  Number.''15)
  _________________________
  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.
  15) Required by LIA-1.

38Meaningful for all floating point types.

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

  static const float_denorm_style has_denorm;

40denorm_present if the type allows denormalized values (variable number
  of exponent bits)16), denorm_absent if the type does not allow  denor-
  malized  values,  and  denorm_indeterminate  if it is indeterminate at
  compile time whether the type allows denormalized values.

41Meaningful for all floating 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  for  all  specializations for which has_infinity != false.
  Required in specializations for which is_iec559 != false.

  static T quiet_NaN() throw();

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

46Meaningful for all specializations for which has_quiet_NaN  !=  false.
  Required in specializations for which is_iec559 != false.

  static T signaling_NaN() throw();

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

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

48Meaningful  for  all  specializations  for  which has_signaling_NaN !=
  false.  Required in specializations for which is_iec559 != false.

  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 for all 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 that wraps around to a
  third number that is less.

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

58Meaningful for all specializations.

  _________________________
  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.

  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 for all 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
    };
  }

1 The rounding mode for floating point arithmetic  is  characterized  by
  the values:

  --round_indeterminate if the rounding style is indeterminable

  --round_toward_zero if the rounding style is toward zero

  --round_to_nearest  if  the  rounding  style  is to the nearest repre-
    sentable value

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

  --round_toward_infinity if the rounding style is toward infinity

  --round_toward_neg_infinity if the rounding style is  toward  negative
    infinity

  18.2.1.4  Type float_denorm_style                   [lib.denorm.style]

  namespace std {
    enum float_denorm_style {
      denorm_indeterminate = -1;
      denorm_absent = 0;
      denorm present = 1;
    };
  }

1 The  presence  or absence of denormalization (variable number of expo-
  nent bits) is characterized by the values:

  --denorm_indeterminate if it cannot be determined whether or  not  the
    type allows denormalized values

  --denorm_absent if the type does not allow denormalized values

  --denorm_present if the type does allow denormalized values

  18.2.1.5  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 that is not ``meaningful'' shall be set to 0 or false.

2 [Example:
  namespace std {
    template<> class numeric_limits<float> {
    public:
      static const bool is_specialized = true;
      inline static float min() throw() { return 1.17549435E-38F; }
      inline static float max() throw() { 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() throw()     { return 1.19209290E-07F; }
      inline static float round_error() throw() { 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()      throw() { return ...; }
      inline static float quiet_NaN()     throw() { return ...; }
      inline static float signaling_NaN() throw() { return ...; }
      inline static float denorm_min()    throw() { 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 header <limits.h>.

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 header <float.h>.

  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 header <stdlib.h>,
  with the following changes:

  abort(void)

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

  --The program is terminated without executing destructors for  objects
    of  automatic  or  static  storage  duration and without calling the
    functions passed to atexit() (_basic.start.term_).

  extern "C" int atexit(void (*f)(void))
  extern "C++" int atexit(void (*f)(void))

  Effects:
    The atexit() functions register the function pointed to by f, to  be
    called without arguments at normal program termination.

4 For  the  execution of a function registered with atexit(), if control
  leaves the function because it provides no handler for a thrown excep-
  tion, terminate() is called (_lib.terminate_).
  Implementation Limits:
    The  implementation  shall  support  the registration of at least 32
    functions.
  Returns:
    The atexit() function returns zero  if  the  registration  succeeds,
    nozero if it fails.

  exit(int status)

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

  --First, objects with static storage duration are destroyed and  func-
    tions  registered by calling atexit are called.  Objects with static
    storage duration are destroyed in the reverse order of  the  comple-
    tion  of their constructor.  (Automatic objects are not destroyed as
    a result of calling exit().)28) Functions registered with atexit are
    called in the reverse order of  their  registration.29)  A  function
    registered with atexit before an object obj1 of static storage dura-
    tion is initialized will not be called until obj1's destruction  has
    completed.   A  function registered with atexit after an object obj2
    of static storage duration is  initialized  will  be  called  before
    obj2's destruction starts.

  --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)

  --Finally, control is returned to the host environment.  If status  is
    zero  or  EXIT_SUCCESS, an implementation-defined form of the status
  _________________________
  28) Objects with automatic storage duration are  all  destroyed  in  a
  program  whose  function main() contains no automatic objects and exe-
  cutes the call to exit().  Control can be transferred directly to such
  a main() by throwing an exception that is caught in main().
  29) A function is called for every time it is registered.
  30) Any C streams associated with cin,  cout,  etc  (_lib.iostream.ob-
  jects_)  are  flushed  and closed when static objects are destroyed in
  the previous phase.  The function tmpfile() is declared in <cstdio>.

    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)

6 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

  namespace std {
    class bad_alloc;
    struct nothrow_t {};
    extern const nothrow_t nothrow;
    typedef void (*new_handler)();
    new_handler set_new_handler(new_handler new_p) throw();
  }
    void* operator new(std::size_t size) throw(std::bad_alloc);
    void* operator new(std::size_t size, const std::nothrow_t&) throw();
    void  operator delete(void* ptr) throw();
    void  operator delete(void* ptr, const std::nothrow_t&) throw();
    void* operator new[](std::size_t size) throw(std::bad_alloc);
    void* operator new[](std::size_t size, const std::nothrow_t&) throw();
    void  operator delete[](void* ptr) throw();
    void  operator delete[](void* ptr, const std::nothrow_t&) throw();
    void* operator new  (std::size_t size, void* ptr) throw();
    void* operator new[](std::size_t size, void* ptr) throw();
    void  operator delete  (void* ptr, void*) throw();
    void  operator delete[](void* ptr, void*) throw();

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

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

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

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

  Effects:
    The allocation function (_basic.stc.dynamic.allocation_) called by a
  _________________________
  31) The macros EXIT_FAILURE and EXIT_SUCCESS are defined in <cstdlib>.

    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   non-null   pointer   to   suitably   aligned    storage
    (_basic.stc.dynamic_),  or  else  throw a bad_alloc exception.  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, throw bad_alloc.

  --Otherwise, the function calls the current new_handler (_lib.new.han-
    dler_).  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(std::size_t size, const std::nothrow_t&) 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   non-null   pointer   to   suitably   aligned   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.han-
    dler_).  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_t&) 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(std::size_t) or operator
    new(std::size_t,const std::nothrow_t&).
  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, which was not invalidated by an inter-
    vening call to operator delete(void*) (_lib.res.on.arguments_).  For
    such a non-null value of ptr, reclaims storage allocated by the ear-
    lier call to the default operator 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[](std::size_t size) throw(std::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.32)
  _________________________

  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(std::size_t).  This requirement is  binding
    on a replacement version of this function.
  Default behavior:
    Returns operator new(size).

  void* operator new[](std::size_t size, const std::nothrow_t&) 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(std::size_t,const std::nothrow_t&).  This
    nothrow version of operator new[] returns a pointer obtained  as  if
    acquired from the ordinary version.
  Default behavior:
    Returns operator new(size,nothrow).

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

  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[](std::size_t)    or    operator
    new[](std::size_t,const std::nothrow_t&).

  _________________________
  32) It is not the direct responsibility of operator new[](std::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, how-
  ever, increase the size argument to operator new[](std::size_t) to ob-
  tain space to store supplemental information.

  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[](std::size_t).33) 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.con-
  straints_).

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

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

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[](std::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 when any part of  the  initialization  in  a
    placement  new  expression  that  invokes  the  library's  non-array
  _________________________
  33) The value must not have been invalidated by an intervening call to
  operator delete[](void*) (_lib.res.on.arguments_).

    placement  operator  new  terminates  by   throwing   an   exception
    (_expr.new_).

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

  Effects:
    Intentionally performs no action.
  Notes:
    Default  function  called  when  any part of the initialization in a
    placement new expression that invokes the library's array  placement
    operator new terminates by throwing an exception (_expr.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.
  Notes:
    The result of calling what() on  the  newly  constructed  object  is
    implementation-defined.

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

  Effects:
    Copies an object of class bad_alloc.

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

  Returns:
    An implementation-defined NTBS.

  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
  additional 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();

  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_han-
    dler.
  Returns:
    0 on the first call, the previous new_handler on subsequent calls.

  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

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

  SEE ALSO: _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 NTBS.
  Notes:
    The  message  may be a null-terminated multibyte string (_lib.multi-
    byte.strings_), suitable for conversion and  display  as  a  wstring
    (_lib.string.classes_, _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.
  Notes:
    The result of calling what() on  the  newly  constructed  object  is
    implementation-defined.

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

  Effects:
    Copies an object of class bad_cast.

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

  Returns:
    An implementation-defined NTBS.
  Notes:
    The  message  may be a null-terminated multibyte string (_lib.multi-
    byte.strings_), suitable for conversion and  display  as  a  wstring
    (_lib.string.classes_, _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.
  Notes:
    The  result  of  calling  what()  on the newly constructed object is
    implementation-defined.

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

  Effects:
    Copies an object of class bad_typeid.

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

  Returns:
    An implementation-defined NTBS.
  Notes:
    The message may be a null-terminated multibyte  string  (_lib.multi-
    byte.strings_),  suitable  for  conversion  and display as a wstring
    (_lib.string.classes_, _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();
    bool uncaught_exception();
  }

  SEE ALSO: _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.multi-
    byte.strings_),  suitable  for  conversion  and display as a wstring
    (_lib.string.classes_, _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.
  Notes:
    The result of calling what() on  the  newly  constructed  object  is
    implementation-defined.

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

  Effects:
    Copies an object of class bad_exception.

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

  Returns:
    An implementation-defined NTBS.
  Notes:
    The  message  may be a null-terminated multibyte string (_lib.multi-
    byte.strings_), suitable for conversion and  display  as  a  wstring
    (_lib.string.classes_, _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  not  return.   See also _except.unex-
    pected_.
  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 exits via an exception
  not allowed by its exception-specification (_except.unexpected_).  May
  also be called directly by the program.
  Effects:
    Calls  the  unexpected_handler  function in effect immediately after
    evaluating  the  throw-expression   (_lib.unexpected.handler_),   if
    called  by  the implementation, or calls the current unexpected_han-
    dler, if called by the program.

  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_).  May also  be  called
  directly by the program.
  Effects:
    Calls  the  terminate_handler  function  in effect immediately after
    evaluating the throw-expression (_lib.terminate.handler_), if called
    by  the implementation, or calls the current terminate_handler func-
    tion, if called by the program.

  18.6.4  uncaught_exception                              [lib.uncaught]

  bool uncaught_exception();

  Returns:
    true after completing evaluation of a throw-expression until  either
    completing initialization of the exception-declaration in the match-
    ing handler or entering unexpected() due  to  the  throw;  or  after
    entering  terminate()  for any reason other than an explicit call to
    terminate().  [Note: This includes stack unwinding  (_except.ctor_).
     --end note]
  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 of these headers are the same as the Standard  C  library
  headers  <stdarg.h>,  <setjmp.h>, <time.h>, <signal.h>, and <stdlib.h>
  respectively, with the following 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.

5 The common subset of the C and C++ languages consists of all  declara-
  tions,  definitions,  and expressions that may appear in a well formed
  C++ program and also in a conforming C program.  A  POF  (``plain  old

  function'')  is  a  function  that uses only features from this common
  subset, and that does not directly or indirectly use any function that
  is  not  a POF.  All signal handlers shall have C linkage.  A POF that
  could be used as a signal handler in a conforming C program  does  not
  produce undefined behavior when used as a signal handler in a C++ pro-
  gram.  The behavior of any other function used as a signal handler  in
  a C++ program is implementation defined.34)

  _________________________
  34)  In  particular, a signal handler using exception handling is very
  likely to have problems