Re: /usr/include/stdatomic.h is not self-contained (fwd from Cygwin list)

Am 09.02.2026 um 15:38 schrieb Corinna Vinschen:

> Therefore we either have to include stdint.h from stdatomic.h, as
> Tomohiro suggested, or we have to rearrange the headers slightly
> and move the FAST definitions into machine/_default_types.h.

I'm not sure if this has changed over the years (decades, even), but the 
stance of the C Standard community always used to be that no standard 
header may ever include any of the others, nor define any things only 
specified to be defined by others than itself.

So in theory it should be allowed to define your own things named, say, 
uint16_t, in any source code that does not #include <stdint.h>, without 
clashing with the standard's definitions.  I.e. code that begins 
something like

#include <stdatomic.h>
typedef unsigned char uint8_t;

must not be flagged for a redefinition of uint8_t.  Identifiers with 
external linkage (i.e. variables and functions) are allowed to cause 
such a clash, typedefs and macros are not.

See C99 7.1.3p1, where it uses the phrase "if any of its associated 
headers is included"