Correct printf format specifier for size_t: %zu or %Iu?
MS Visual Studio didn't support %zu printf specifier before VS2013. Starting from VS2013 (e.g. _MSC_VER >= 1800) %zu is available.
As an alternative, for previous versions of Visual Studio if you are printing small values (like number of elements from std containers) you can simply cast to an int and use %d:
printf("count: %d\n", (int)str.size()); // less digital ink spent// or:printf("count: %u\n", (unsigned)str.size());
Microsoft's C compiler does not catch up with the latest C standards. It's basically a C89 compiler with some cherry-picked features from C99 (e.g. long long). So, there should be no surprise that something isn't supported (%zu appeared in C99).
The Microsoft documentation states:
The
hh,j,z, andtlength prefixes are not supported.
And therefore %zu is not supported.
It also states that the correct prefix to use for size_t is I – so you'd use %Iu.