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 

I am compiling this program:

#include <stdio.h>  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); } 

with warnings and c11 standard:

gcc -Wall -Wextra -Wpedantic -std=c11 test_size_t.c 

and I get these warnings:

   test_size_t.c: In function 'main':     test_size_t.c:6:14: warning: format '%lu' expects argument of type 'long unsigned int', but argument 2 has type 'size_t {aka long long unsigned int}' [-Wformat=]       printf("a=%lu\n",a);                 ~~^                 %I64u     test_size_t.c:6:14: warning: format '%lu' expects argument of type 'long unsigned int', but argument 2 has type 'size_t {aka long long unsigned int}' [-Wformat=]       printf("a=%lu\n",a);                 ~~^                 %I64u     test_size_t.c:7:14: warning: unknown conversion type character 'l' in format [-Wformat=]       printf("a=%llu\n",a);                   ^     test_size_t.c:7:9: warning: too many arguments for format [-Wformat-extra-args]       printf("a=%llu\n",a);              ^~~~~~~~~~     test_size_t.c:7:14: warning: unknown conversion type character 'l' in format [-Wformat=]       printf("a=%llu\n",a);                   ^     test_size_t.c:7:9: warning: too many arguments for format [-Wformat-extra-args]       printf("a=%llu\n",a);              ^~~~~~~~~~     test_size_t.c:8:13: warning: unknown conversion type character 'z' in format [-Wformat=]       printf("a=%zu\n",a);                  ^     test_size_t.c:8:9: warning: too many arguments for format [-Wformat-extra-args]       printf("a=%zu\n",a);              ^~~~~~~~~     test_size_t.c:8:13: warning: unknown conversion type character 'z' in format [-Wformat=]       printf("a=%zu\n",a);                  ^     test_size_t.c:8:9: warning: too many arguments for format [-Wformat-extra-args]       printf("a=%zu\n",a);              ^~~~~~~~~     test_size_t.c:9:9: warning: ISO C does not support the 'I64' ms_printf length modifier [-Wformat=]       printf("a=%I64u\n",a);          ^~~~~~~~~~~     test_size_t.c:9:9: warning: ISO C does not support the 'I64' ms_printf length modifier [-Wformat=] 

I would like to printf a size_t without warning but don't know the correct format specifier in this situation.