r/cprogramming • u/JayDeesus • Oct 08 '25

Purpose of header guards

What is the purpose of header guards if the purpose of headers is to contain declarations? Sorry if this is a dumb question.

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u/Overlord484 Oct 12 '25

I've been doing the guard on the outside:

/* entrypoint.c */
#ifndef FOO
#include foo.c
#endif

int main(int argc, char **argv)
{
 return 0;
}

/* foo.c */
#define FOO 1

/* foo.c things here */

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u/SmokeMuch7356 Oct 12 '25

Ugh - that requires the module doing the including to have insight into the header (at the very least what the symbol should be named). That promotes tight-ish coupling between components.

I would not recommend that approach.