bug with __has_include and valgrind header

[lucas-mior]

The following program does not compile:

// chibicc

void function(void) {
    // this function is here just to show that the problem is not on line 1
}

#if defined(__has_include) && __has_include(<valgrind/valgrind.h>)
#include <valgrind/valgrind.h>
#endif

#include "stdio.h"

int main(void) {
    printf("This program should compile.\n");
    return 0;
}

The error message is:

main.c:1: 0
          ^ not a function

Also note that the error message says line 1, independent of where the valgrind macro directive is.

[fuhsnn]

It's simply because __has_include is not implemented in chibicc.

The defined() guard is ineffective, if a compiler doesn't implement the __has_xxx directive it becomes an evaluation of:

#if 0 && 0(...)

that's where the "0" not a function came from.

The same issue can be observed (albeit with better error message) with not so recent GCC and __has_feature https://godbolt.org/z/MjKMEGM7E

The guard has to be an outer level like:

#if defined(__has_include)
# if __has_include(...)
# endif
#endif

[lucas-mior]

Thanks for the tip. It had never occured to me that the preprocessor can't do shortcircuiting if the syntax is wrong.
But do you agree that the error message is not very helpful? It would be better to at least reference the correct line.