Portable printf format specifier for 64 bit hexadecimal? [duplicate]

Question

What printf format specifier can I use to print a 64 bit unsigned integer in hexadecimal notation across 32/64 bit and Windows/POSIX? The closest I've seen is %llX but I'm not sure that is portable enough. Answers that ignore older compilers (e.g. Visual Studio 2010) are acceptable.

Answer 1

The PRIx64 macro in <inttypes.h> is what you're looking for.

It's a string token, so you can use it as: fprintf(stdout, "answer = %"PRIx64"\n", val);

Since you specify %llX, you probably want uppercase; use: PRIX64