How to printf a size_t without warning in mingw-w64 gcc 7.1?

Question

I am using the mingw-w64 (x64) fork of minGW as prepared on nuwen.net. This is from the 7.1 version of gcc :

gcc --version
gcc (GCC) 7.1.0

Answer 1

The alternative solution as mentioned in comments is to toss in the __USE_MINGW_ANSI_STDIO compiler switch:

#define __USE_MINGW_ANSI_STDIO 1

#include 

int main(void)
{
    size_t a = 100;
    printf("a=%lu\n",a);
    printf("a=%llu\n",a);
    printf("a=%zu\n",a);
    printf("a=%I64u\n",a);
}

This makes the code compile as expected and gcc now gives the appropriate warnings:

warning: format '%lu' expects argument of type 'long unsigned int', but argument 2 has type 'size_t' [-Wformat=]  
warning: ISO C does not support the 'I' printf flag [-Wformat=]  
warning: format '%u' expects argument of type 'unsigned int', but argument 2 has type 'size_t' [-Wformat=]  

---

Alternatively you can define the macro on command line with -D__USE_MINGW_ANSI_STDIO=1