VMS Help CC, Language topics, Predefined Macros  *Conan The Librarian (sorry for the slow response - running on an old VAX)

  In addition to the ANSI-compliant, implementation-independent
  macros described in the Compaq C Language Reference Manual, Compaq
  C for OpenVMS systems provides the following predefined macros:

1 - System Identification Macros

  Each implementation of the Compaq 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 Compaq 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
             vax                   __vax
             VAX                   __VAX
             vaxc                  __vaxc
             VAXC                  __VAXC
             vax11c                __vax11C
             VAX11C                __VAX11C
              ---                  __DECC
              ---                  __STDC__
                                   __STDC_HOSTED__
                                   __STDC_VERSION__
                                   __STDC_ISO_10646__
                                   __MIA

  Note that __STDC__ is defined only in strict ANSI C mode.

  Predefined macros (with the exception of vms_version, VMS_VERSION,
  __vms_version and __VMS_VERSION) 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 Compaq 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).

2 - 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_ANSI89
  __DECC_MODE_VAXC       !  /STANDARD=VAXC
  __DECC_MODE_COMMON     !  /STANDARD=COMMON
  __STDC__               !  /STANDARD=ANSI89, /STANDARD=RELAXED_ANSI89
  __STDC_VERSION__       !  /STANDARD=ISOC94
  __MS                   !  /STANDARD=MS

3 - Floating Point Macros

  Compaq 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

4 - RTL Standards Macros

  Compaq C defines the following macros that you can explicitly
  define (using the /DEFINE qualifier or the #define preprocessor
  directive) to control which Compaq 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

5 - 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 running the Compaq C compiler in strict ANSI C mode
  (/STANDARD=ANSI89), 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 in strict ANSI mode.

  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

6 - 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.

7 - 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__);

8 - FILE

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

  Example:

       printf("file %s", __FILE__);

9 - 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__);

10 - 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.