Is it possible to determine at compile time whether an implementation provides exact-width integer types?

Question

Is it possible to determine at compile time whether an implementation provides exact-width integer types? Sample code (wanted):

#include <stdint.h>

#if HAS_EXACT_WIDTH_INTEGER_TYPES
uint32_t    i;
#else
/* handle the case */
#endif

Reason of the question: writing an adaptable code, which does not lead to compile time errors if an implementation does not provide exact-width integer types.

See this answer: https://stackoverflow.com/questions/59552571/how-to-check-if-fixed-width-integers-are-defined — Daniel Kleinstein, Jul 25 '21 at 20:16
@KamilCuk Right, thanks! The same way is used to determine if an implementation supports `_Float16`: `#ifdef FLT16_MAX`. — pmor, Jul 25 '21 at 20:17

score 5 · Accepted Answer · answered Jul 25 '21 at 20:16

C11/C17 7.20p4:

For each type described herein that the implementation provides, 261) <stdint.h> shall declare that typedef name and define the associated macros. Conversely, for each type described herein that the implementation does not provide, <stdint.h> shall not declare that typedef name nor shall it define the associated macros. An implementation shall provide those types described as ''required'', but need not provide any of the others (described as ''optional'').

i.e. uint32_t exists iff #defined UINT32_MAX, etc.

Is it possible to determine at compile time whether an implementation provides exact-width integer types?

1 Answers1