c - cross-platform printing of 64-bit integers with printf

Question

In Windows, it is "%I64d". In Linux and Solaris, it is "%lld".
If I want to write cross-platform printfs that prints long long values: what is good way of doing so ?

long long ll;
printf(???, ll);

Answer 1

There are a couple of approaches.

You could write your code in C99-conforming fashion, and then supply system-specific hacks when the compiler-writers let you down. (Sadly, that's rather common in C99.)

#include <stdint.h>
#include <inttypes.h>

printf("My value is %10" PRId64 "
", some_64_bit_expression);

If one of your target systems has neglected to implement <inttypes.h> or has in some other way fiendishly slacked off because some of the type features are optional, then you just need a system-specific #define for PRId64 (or whatever) on that system.

The other approach is to pick something that's currently always implemented as 64-bits and is supported by printf, and then cast. Not perfect but it will often do:

printf("My value is %10lld
", (long long)some_64_bit_expression);