Saturday, May 09, 2009


Magic of C preprocessor

Curtis Krauskopf discusses a neat trick which forces C preprocessor to merge __FILE__ and __LINE__ as one string, which isn't straightforward since __FILE__ is a string but __LINE__ is an integer.

It turns out you can solve the problem with two additional macros:

#include <stdio.h>
#define STRINGIFY(x) #x
#define AT __FILE__ ":" TOSTRING(__LINE__)
void error(const char *location, const char *msg)
  printf("Error at %s: %s\n", location, msg);
int main(int , char**)
  error(AT, "fake error");
  return 0;

Now, if only someone could find a way to merge __func__ and __LINE__ ....


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