C/C++ Programmer's Guide (G06.25+)

Preprocessor Directives and Macros
HP C/C++ Programmer’s Guide for NonStop Servers—429301-002
12-12
Predefined Symbols
void foo (void) {
printf ("Entering function %s\n", __FUNCTION__);
printf ("ch[] was in function \"%s\"\n", ch);
};
int main (void) {
foo ();
}
The output from the preceding code is:
Entering function foo
ch[] was in function ""
Predefined Symbols
The compiler provides three predefined preprocessor symbols: __TANDEM, __INT32,
and __XMEM.
You can use the __TANDEM symbol to increase the portability of your programs.
Enclose system-dependent source text in an if section that uses #ifdef or #ifndef
to test for the existence of the __TANDEM symbol.
The predefined preprocessor symbol __INT32 is defined by the TNS C compiler and
CFront when the WIDE pragma is present. The predefined preprocessor symbol
__XMEM is defined by the TNS C compiler and Cfront when the XMEM pragma is
present. The native compilers always define the preprocessor symbols __INT32 and
__XMEM.
The __INT32 and __XMEM preprocessor symbols affect the visibility of declarations in
header files.
Variadic Macros
Two variants of variadic macro definitions can be invoked in native C with a variable
number of arguments. To use these extensions, you must compile with extensions
enabled.
•
One variant of variadic macro is the C9X form, described in section 6.8.3 of the
Working Draft, 1997-11-21, WG14/N794 J11/97-158 of the Proposed ISO C
Standard.
For example:
#define D(fmt, ...) printf(fmt, __VA_ARGS__)
/* The "..." matches an arbitrary positive number of macro
arguments that can be referred to by __VA_ARGS__
(includes the separating commas) */
D("%c%s\n" , ’E’, "DG");
/* Expands to "printf("%c%s\n", ’E’, "DG");" */