libsm : C Language Portability Macros

Description

__P(parameterlist)

This macro is used to write portable function prototypes. For example,

int foo __P((int));

__CONCAT(x,y)

This macro concatenates two tokens x and y, forming a single token xy. Warning: make sure there is no white space around the arguments x and y.

__STRING(x)

This macro converts the token sequence x into a string literal.

__BEGIN_DECLS, __END_DECLS

These macros are used to write C header files that are compatible with C++ compilers. Put __BEGIN_DECLS before the first function or variable declaration in your header file, and put __END_DECLS after the last function or variable declaration.

const, signed, volatile

For pre-ANSI C compilers, const, signed and volatile are defined as empty macros. This means you can use these keywords without introducing portability problems.

SM_DEAD(function_declaration)

This macro modifies a prototype of a function that does not return to its caller. With some versions of gcc, this will result in slightly better code, and can suppress some useless warnings produced by gcc -Wall. For example,

SM_DEAD(void exit __P((int)));

SM_UNUSED(variable_declaration)

This macro modifies a definition of an unused local variable, global variable or function parameter in order to suppress compiler warnings. Examples:

SM_UNUSED(static const char Id[]) = "@(#)$Id: cdefs.html 1073 2021-06-27 05:01:23Z  $";
void
foo(x)
	SM_UNUSED(int x);
{
	SM_UNUSED(int y) = 0;
	return 0;
}
void
bar(SM_UNUSED(int x))
{
	return 0;
}