C – printf Format Specifiers for uint32_t and size_t

c++printf

I have the following

size_t   i = 0;
uint32_t k = 0;

printf("i [ %lu ] k [ %u ]\n", i, k);

I get the following warning when compiling:

format ‘%lu’ expects type ‘long unsigned int’, but argument has type ‘uint32_t’

When I ran this using splint I got the following:

Format argument 1 to printf (%u) expects unsigned int gets size_t: k

Many thanks for any advice,

Best Answer

Try

#include <inttypes.h>
...

printf("i [ %zu ] k [ %"PRIu32" ]\n", i, k);

The z represents an integer of length same as size_t, and the PRIu32 macro, defined in the C99 header inttypes.h, represents an unsigned 32-bit integer.

Related Solutions

C Programming – Handling printf with sizeof on 32 vs 64 Platforms

Portable printf identifiers are provided in the include file inttypes.h or here.

This include file has many portable identifiers for your specific runtime. For your example, you want PRIuPTR, which means "PRintf Identifier unsigned with size of up to a pointer's size".

Your example will then be:

printf("The amount of RAM used is %" PRIuPTR, anIntVariable*sizeof(double) );

Results on 64bit Linux with GCC 4.3 (int anIntVariable = 1):

$ gcc test.c -m32 -o test && ./test
The amount of RAM used is 8
$ gcc test.c -o test && ./test
The amount of RAM used is 8

For completeness sake, there are identifiers for scanf too, whose prefixes are SCN.

GCC – printf for size_t

printf("%zu", sizeof(whatever));

Best Answer

Related Solutions

C Programming – Handling printf with sizeof on 32 vs 64 Platforms

GCC – printf for size_t

Related Question