System_Identification_Macros

 Each implementation of the HP C compiler automatically defines
 macros that you can use to identify the system on which the program
 is running.  These macros can assist in writing code that executes
 conditionally, depending on the architecture or operating system on
 which the program is running.

 The following table lists the traditional and new spellings of
 these predefined macro names for HP C on OpenVMS systems.  Both
 spellings are defined for each macro unless ANSI C mode is in
 effect (/STANDARD=ANSI89), in which case only the new spellings are
 defined.

       Traditional spelling      New spelling

            vms                   __vms
            VMS                   __VMS
            vms_version           __vms_VERSION
            VMS_VERSION           __VMS_VERSION
                                  __VMS_VER
                                  __DECC_VER
                                  __DECCXX_VER
            vaxc                  __vaxc
            VAXC                  __VAXC
            vax11c                __vax11C
            VAX11C                __VAX11C
             ---                  __DECC
             ---                  __STDC__
                                  __STDC_HOSTED__
                                  __STDC_VERSION__
                                  __STDC_ISO_10646__
                                  __MIA



 On OpenVMS I64 Systems, HP C also supports the following predefined
 system identification macro names in all compiler modes:

 __ia64
 __ia64__
 __32BITS
 __INITIAL_POINTER_SIZE

 Predefined macros (with the exception of __STDC_VERSION__,
 __STDC_ISO_10646__, vms_version, VMS_VERSION, __vms_version,
 __VMS_VERSION, and __INITIAL_POINTER_SIZE) are defined as 1 or 0,
 depending on the system you're compiling on (VAX or Alpha
 processor), the compiler defaults, and the qualifiers used.  For
 example, if you compiled using G_floating format, then __D_FLOAT
 and __IEEE_FLOAT (Alpha processors only) are predefined to be 0,
 and __G_FLOAT is predefined as if the following were included
 before every compilation unit:

 #define  __G_FLOAT  1

 These macros can assist in writing code that executes
 conditionally.  They can be used in #elif, #if, #ifdef, and #ifndef
 directives to separate portable and nonportable code in a HP C
 program.  The vms_version, VMS_VERSION, __vms_version, and
 __VMS_VERSION macros are defined with the value of the OpenVMS
 version on which you are running (for example, Version 6.0).

 The __STDC__ macro is defined to 1 for /STANDARD options ANSI89,
 C99, LATEST and MIA.  It is defined to 2 for /STANDARD=RELAXED and
 to 0 for /STANDARD=MS.  It is not defined for /STANDARD options
 VAXC and COMMON.

 The __STDC_HOSTED__ macro is defined to 1 for /STANDARD=c99 and
 /STANDARD=LATEST.  It is not defined for all other /STANDARD
 keywords.

 The __STDC_VERSION__ macro is defined to 199901L for /STANDARD
 keywords C99, LATEST, RELAXED, MS, PORTABLE.  It is defined to
 199409L when the ISOC94 keyword is specified alone or with the
 ANSI89, MIA, RELAXED, MS, PORTABLE, or COMMON modes.  The macro is
 undefined for the VAXC keyword or for keywords ANSI89, MIA, or
 COMMON without ISOC94 specified.

 The __STDC_ISO_10646__ macro evaluates to an integer constant of
 the form yyyymmL (for example, 199712L), intended to indicate that
 values of type wchar_t are the coded representations of the
 characters defined by ISO/IEC 10646, along with all amendments and
 technical corrigenda as of the specified year and month.


Compiler_Mode_Macros

 The following predefined macros are defined as 1 if the
 corresponding compiler mode is selected (Otherwise, they are
 undefined):

 __DECC_MODE_STRICT     !  /STANDARD=ANSI89
 __DECC_MODE_RELAXED    !  /STANDARD=RELAXED
 __DECC_MODE_VAXC       !  /STANDARD=VAXC
 __DECC_MODE_COMMON     !  /STANDARD=COMMON
 __STDC__               !  /STANDARD=ANSI89, /STANDARD=RELAXED
 __STDC_VERSION__       !  /STANDARD=ISOC94
 __MS                   !  /STANDARD=MS


Floating_Point_Macros

 HP C automatically defines the following predefined macros
 pertaining to the format of floating-point variables.  You can use
 them to identify the format with which you are compiling your
 program:

 __D_FLOAT
 __G_FLOAT
 __IEEE_FLOAT
 _IEEE_FP
 __X_FLOAT


RTL_Standards_Macros

 HP C defines the following macros that you can explicitly define
 (using the /DEFINE qualifier or the #define preprocessor directive)
 to control which HP C RTL functions are declared in header files
 and to obtain standards conformance checking:

 _XOPEN_SOURCE_EXTENDED
 _XOPEN_SOURCE
 _POSIX_C_SOURCE
 _ANSI_C_SOURCE
 _VMS_V6_SOURCE
 _DECC_V4_SOURCE
 __BSD44_CURSES
 __VMS_CURSES
 _SOCKADDR_LEN


__HIDE_FORBIDDEN_NAMES

 The ANSI C standard specifies exactly what identifiers in the
 normal name space are declared by the standard header files.  A
 compiler is not free to declare additional identifiers in a header
 file unless the identifiers follow defined rules (the identifier
 must begin with an underscore followed by an uppercase letter or
 another underscore).

 When you compile with HP C using any values of /STANDARD that set
 strict C standard conformance (ANSI89, MIA, C99, and LATEST),
 versions of the standard header files are included that hide many
 identifiers that do not follow the rules.  The header file
 <stdio.h>, for example, hides the definition of the macro TRUE.
 The compiler accomplishes this by predefining the macro
 __HIDE_FORBIDDEN_NAMES for the above-mentioned /STANDARD values.

 You can use the command line qualifier
 /UNDEFINE="__HIDE_FORBIDDEN_NAMES" to prevent the compiler from
 predefining this macro, thus including macro definitions of the
 forbidden names.

 The header files are modified to only define additional VAX C names
 if __HIDE_FORBIDDEN_NAMES is undefined.  For example, <stdio.h>
 might contain the following:

         #ifndef __HIDE_FORBIDDEN_NAMES
         #define TRUE    1
         #endif


CC$gfloat

 When you compile using the /G_FLOAT qualifier, CC$gfloat is defined
 as 1.  When you compile without the /G_FLOAT qualifier, CC$gfloat
 is defined as 0.  The CC$gfloat macro is provided for compatiblity
 with VAX C.  The __G_FLOAT predefined macro should be used instead.


__DATE__

 The __DATE__ macro evaluates to a string specifying the date on
 which the compilation started.  The string presents the date in the
 form "Mmm dd yyyy" The names of the months are those generated by
 the asctime library function.  The first d is a space if dd is less
 than 10.

 Example:

      printf("%s",__DATE__);


__FILE__

 The __FILE__ macro evaluates to a string literal specifying the
 file specification of the current source file.

 Example:

      printf("file %s", __FILE__);



__LINE__

 The __LINE__ macro evaluates to a decimal constant specifying the
 number of the line in the source file containing the macro
 reference.

 Example:

      printf("At line %d in file %s", __LINE__, __FILE__);



__TIME__

 The __TIME__ macro evaluates to a string specifying the time that
 the compilation started.  The time has the following format:

      hh:mm:ss

 Example:

      printf("%s", __TIME__);

 The value of this macro remains constant throughout the translation
 unit.