Re: "A diagram of C23 basic types"

On 03/04/2025 23:39, Janis Papanagnou wrote:

On 03.04.2025 16:58, David Brown wrote:

[...]
>
I know people can use pre-processor conditional compilation based on
__STDC_VERSION__ to complain if code is compiled with an unexpected or
unsupported standard, but few people outside of library header authors
actually do that.  I'd really like :
>
     #pragma STDC VERSION C17
>
to force the compiler to use the equivalent of "-std=c17
-pedantic-errors" in gcc.

 (I understand the wish to have that #pragma supported.)
 Can there be linking problems when different "C" modules have
been compiled with different '-std=cXX' or '#pragma STDC ...'
settings? - The question just occurred to me.
 

I don't think there will be any non-obvious issues - at least, not unless you have code that relies on undefined behaviour.  Of course you will also have trouble if you have a TU compiled for C90 that defines its own "quick_exit" function and you want to link that with a C11 TU using the standard library "quick_exit" function.  The great majority of the changes in the standard apply within the translation unit, or are new library functions, or extensions to existing ones (like additional features in "printf").
It is not at all uncommon to have static libraries compiled with one C standard flag linked to code compiled with a different flag.
(Of course this is all implementation-dependent.)