[Bug libstdc++/97044] New: Undefined format macros because of include order on AIX

[clement.chigot at atos dot net]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=97044

            Bug ID: 97044
           Summary: Undefined format macros because of include order on
                    AIX
           Product: gcc
           Version: unknown
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: libstdc++
          Assignee: unassigned at gcc dot gnu.org
          Reporter: clement.chigot at atos dot net
  Target Milestone: ---

On AIX, C++ format macros like "PRIu32" might not be defined even if
"cinttypes" is included. It happends when other headers which have a dependency
on "inttypes.h" are included before. 
On AIX, __STDC_FORMAT_MACROS must be defined before "sys/inttypes.h" is
included in order to have these macros defined. But with for example <cstring>,
as "string.h" includes "sys/types" which included "sys/inttypes.h",
__STDC_FORMAT_MACROS won't be defined when "sys/inttypes.h" is first included
thus the format macros won't be defined. 

This program works on Linux but not on AIX. 
#include <cstring>
#include <cinttypes>
#include <iostream>

int main(){
#ifdef PRIu32
  std::cout << "PRIu32 defined" << std::endl;
#else
  std::cout << "PRIu32 not defined" << std::endl;
#endif
}

My question is what are the G++ standards saying on that ? Should <cinttypes>
always defined "PRIu32"-like macros ? Or does the developers should be careful
the order when are included the headers or always add -D__STDC_FORMAT_MACROS ?  

I would clearly go for one. Especially, because knowing that "#include
<cstring>" must be after "#include <cinttypes>" if you want to use "PRIu32" is 
not obvious. 

Clément