In addition to the ANSI-compliant, implementation-independent macros described in the HP C Language Reference Manual, The VSI C compiler provides the following predefined macros:
1 – System Identification Macros
Each implementation of the VSI 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 VSI 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, VSI 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 VSI 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.
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 __DECC_MODE_VAXC ! /STANDARD=VAXC __DECC_MODE_COMMON ! /STANDARD=COMMON __STDC__ ! /STANDARD=ANSI89, /STANDARD=RELAXED __STDC_VERSION__ ! /STANDARD=ISOC94 __MS ! /STANDARD=MS
3 – Floating Point Macros
VSI 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
4 – RTL Standards Macros
VSI C defines the following macros that you can explicitly define (using the /DEFINE qualifier or the #define preprocessor directive) to control which VSI 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 you compile with VSI 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
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.