Function-like Macros

3.2 Function-like Macros

You can also define macros whose use looks like a function call. These are called function-like macros. To define a function-like macro, you use the same ‘#define’ directive, but you put a pair of parentheses immediately after the macro name. For example,

#define lang_init()  c_init()
lang_init()
     ==> c_init()

A function-like macro is only expanded if its name appears with a pair of parentheses after it. If you write just the name, it is left alone. This can be useful when you have a function and a macro of the same name, and you wish to use the function sometimes.

extern void foo(void);
#define foo() /* optimized inline version */
...
  foo();
  funcptr = foo;

Here the call to foo() will use the macro, but the function pointer will get the address of the real funct