Can a C macro contain temporary variables?

Question

I have a function that I need to macro\'ize. The function contains temp variables and I can\'t remember if there are any rules about use of temporary variables in macro subs

Answer 1

Eldar's answer shows you most of the pitfalls of macro programming and some useful (but non standard) gcc extension.

If you want to stick to the standard, a combination of macros (for genericity) and inline functions (for the local variables) can be useful.

inline
long fooAlloc(void *f, size_t size)
{
   size_t      i1, i2;
   double   *data[7];

   /* do something */
   return 42;
}


#define ALLOC_FOO(T) fooAlloc(malloc(sizeof(T)), sizeof(T))

In such a case using sizeof only evaluates the expression for the type at compile time and not for its value, so this wouldn't evaluate F twice.

BTW, "sizes" should usually be typed with size_t and not with long or similar.

Edit: As to Jonathan's question about inline functions, I've written up something about the inline model of C99, here.