Prefixing function calls with macros

Question

Im running into an issue where I need to be able to modify C function calls via a macro.

The basic structure is like this:

#define foo bar
foo_1(x);
foo_2(x);
foo_3(x);

What I want is for

bar_1(x);
bar_2(x);
bar_3(x);

to be called, however the string macro does not seem to replace the prefixed part of the calls.

Can someone point me in the proper direction?

Answer 1

Macros only apply to full tokens (thank God - they're bad enough as is). In other words, #define foo bar only affects the identified foo , not the identifier foo_1 , because that's not the same token.

If you can't modify the calling code, there is no way to achieve what you want. Use a text editor's search&replace or something like that.

If what you really want is a snippet of function calling code that you can adjust to different name prefixes as needed, you can write it like this:

foo(1)(x);
foo(2)(x);
foo(3)(x);

and before you include this snippet, you define something like this:

#define foo(i) bar_ ## i

Answer 2

Use string concatenation :

➤ cat try.h
#define mymacro(msv) bar_##msv
mymacro(1)(x);
➤ gcc -E try.h
# 1 "try.h"
# 1 "<built-in>"
# 1 "<command-line>"
# 1 "try.h"

bar_1(x);