snippet from <Writing Clean Code>

custom_assert.h

 #ifdef DEBUG
     void _Assert(char*, unsigned);
     #define ASSERT(f)     \
          if(f)     \
               NULL;     \
          else     \
               _Assert(__FILE__, __LINE__)
#else
     #define ASSERT(f) NULL
#endif

void _Assert(char* strFile, unsigned uLine) {
     fflush(stdout);
     fprintf(stderr, "\nAssertion failed: %s, line %u\n", strFile, uLine);
     fflush(stdeer);
     abort();     // exit with error code 3
}