______________________________________________________________________

  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
  (_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 The headers <limits>, <climits>, and         <cfloat>  supply  charac­
  teristics of implementation-dependent fundamental types (_basic.funda­
  mental_).

  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 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;

    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 = 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 bool has_denorm = false;
      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();

  Minimum finite value.2)

1 For floating types with denormalization, returns the minimum  positive
  normalized value.

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

  static T max() throw();

  Maximum finite value.3)
  _________________________
  2) Equivalent to CHAR_MIN, SHRT_MIN, FLT_MIN, DBL_MIN, etc.
  3) Equivalent to CHAR_MAX, SHRT_MAX, FLT_MAX, DBL_MAX, etc.

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

  static const int  digits;

  Number of radix digits which can be represented without change.

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

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

  static const int  digits10;

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

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

  static const bool is_signed;

  True if the type is signed.

7 Meaningful for all specializations.

  static const bool is_integer;

  True if the type is integer.

8 Meaningful for all specializations.

  static const bool is_exact;

  True 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.

9 Meaningful for all specializations.

  static const int  radix;

  For floating types, specifies the base or radix of the exponent repre­
  sentation (often 2).6)
  _________________________
  4) Equivalent to FLT_MANT_DIG, DBL_MANT_DIG, LDBL_MANT_DIG.
  5) Equivalent to FLT_DIG, DBL_DIG, LDBL_DIG.
  6) Equivalent to FLT_RADIX.

10For integer types, specifies the base of the representation.7)

11Meaningful for all specializations.

  static T epsilon() throw();

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

12Meaningful for all floating point types.

  static T round_error() throw();

  Measure of the maximum rounding error.9)

  static const int  min_exponent;

  Minimum negative integer such that radix raised to the  power  of  one
  less than that integer is a normalized floating point number.10)

13Meaningful for all floating point types.

  static const int  min_exponent10;

  Minimum  negative  integer such that 10 raised to that power is in the
  range of normalized floating point numbers.11)

14Meaningful for all floating point types.

  static const int  max_exponent;

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

15Meaningful for all floating point types.

  static const int  max_exponent10;
  _________________________
  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.
  12) Equivalent to FLT_MAX_EXP, DBL_MAX_EXP, LDBL_MAX_EXP.

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

16Meaningful for all floating point types.

  static const bool has_infinity;

  True if the type has a representation for positive infinity.

17Meaningful for all floating point types.

18Shall be true for all specializations in which is_iec559 != false.

  static const bool has_quiet_NaN;

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

19Meaningful for all floating point types.

20Shall be true for all specializations in which is_iec559 != false.

  static const bool has_signaling_NaN;

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

21Meaningful for all floating point types.

22Shall be true for all specializations in which is_iec559 != false.

  static const bool has_denorm;

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

23Meaningful for all floating point types.

  static const bool has_denorm_loss;

  True if loss of accuracy is detected as a denormalization loss, rather
  than as an inexact result.17)
  _________________________
  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.
  16) Required by LIA-1.
  17) See IEC 559.

  static T infinity() throw();

  Representation of positive infinity, if available.18)

24Meaningful for all specializations for which  has_infinity  !=  false.
  Required in specializations for which is_iec559 != false.

  static T quiet_NaN() throw();

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

25Meaningful  for  all specializations for which has_quiet_NaN != false.
  Required in specializations for which is_iec559 != false.

  static T signaling_NaN() throw();

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

26Meaningful for all  specializations  for  which  has_signaling_NaN  !=
  false.  Required in specializations for which is_iec559 != false.

  static T denorm_min() throw();

  Minimum positive denormalized value.21)

27Meaningful for all floating point types.

28In  specializations for which has_denorm == false, returns the minimum
  positive normalized value.

  static const bool is_iec559;

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

29Meaningful for all floating point types.

  static const bool is_bounded;

  True  if the set of values representable by the type is finite.23) All
  _________________________
  18) Required by LIA-1.
  19) Required by LIA-1.
  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.

  built-in types are bounded, this member would be false  for  arbitrary
  precision types.

30Meaningful for all specializations.

  static const bool is_modulo;

  True  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.

31Generally,  this  is false for floating types, true for unsigned inte­
  gers, and true for signed integers on most machines.

32Meaningful for all specializations.

  static const bool traps;

  true if trapping is implemented for the type.25)

33Meaningful for all specializations.

  static const bool tinyness_before;

  true if tinyness is detected before rounding.26)

34Meaningful for all floating point types.

  static const float_round_style round_style;

  The rounding style for the type.27)

35Meaningful 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]

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

  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

  --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  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() 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:

  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, 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
    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
  _________________________
  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>.
  31) The macros EXIT_FAILURE and EXIT_SUCCESS are defined in <cstdlib>.

  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(size_t size) throw(std::bad_alloc);
    void* operator new(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[](size_t size) throw(std::bad_alloc);
    void* operator new[](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  (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_, _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(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.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(size_t size, const 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    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.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(size_t)   or   operator
    new(size_t,const 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[](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.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(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_t&) throw();

  _________________________
  32) 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.

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

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

  void* operator new(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[](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
  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();
  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_han­
    dler.
  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

  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.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.

      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.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.

      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.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: 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.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.

      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.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 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 an exception of class bad_exception or of any  class  directly
    or indirectly derived from bad_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 when a function exits via  an  exception  not  allowed  by  its
  exception-specification (_except.unexpected_).
  Effects:
    Calls  the  unexpected_handler  function in effect immediately after
    evaluating the throw-expression (_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 terminate_handler function  in  effect  immediately  after
    evaluating the throw-expression (_lib.terminate.handler_).

  18.6.4  uncaught_exception                              [lib.uncaught]

  bool uncaught_exception();

  Returns:
    true  after  completing  evaluation of a throw-expression until com­
    pleting initialization of the exception-declaration in the  matching
    handler   (_except.uncaught_).    This   includes   stack  unwinding
    (_except.ctor_).
  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.