DMARC-Filter: OpenDMARC Filter v1.4.2 delorie.com 61823d6Y066549
DMARC-Filter: OpenDMARC Filter v1.4.2 sourceware.org A430148F3427
Message-Id: <1770515074285.3371994028.3268673411@ezweb.ne.jp>
To: cygwin AT cygwin DOT com
Subject: /usr/include/stdatomic.h is not self-contained
Date: Sun, 08 Feb 2026 02:02:48 +0000
User-Agent: Vivaldi Mail/7.8.3925.62
MIME-Version: 1.0
From: kikairoya via Cygwin <cygwin AT cygwin DOT com>
Reply-To: kikairoya <kikairoya AT gmail DOT com>
Content-Transfer-Encoding: 7bit
Content-Type: text/plain; charset="us-ascii"; Format="flowed"
Sender: "Cygwin" <cygwin-bounces~archive-cygwin=delorie DOT com AT cygwin DOT com>

Hello,

I noticed that /usr/include/stdatomic.h is not self-contained due to lack 
of including <stdint.h>.


$ echo '#include "/usr/include/stdatomic.h"' | gcc -xc - -fsyntax-only
In file included from <stdin>:1:
/usr/include/stdatomic.h:207:17: error: unknown type name 'int_least8_t'
   207 | typedef _Atomic(int_least8_t)           atomic_int_least8_t;
       |                 ^~~~~~~~~~~~
/usr/include/stdatomic.h:208:17: error: unknown type name 'uint_least8_t'
   208 | typedef _Atomic(uint_least8_t)          atomic_uint_least8_t;
       |                 ^~~~~~~~~~~~~
(snip)

$ echo '#include "/usr/include/stdatomic.h"' | gcc -xc - -fsyntax-only 
-include stdint.h


It's normally unaffected since gcc uses its own <stdatomic.h>.


$ echo '#include <stdatomic.h>' | gcc -xc - -fsyntax-only


$ echo '#include <stdatomic.h>' | gcc -xc - -fsyntax-only -H
. /usr/lib/gcc/x86_64-pc-cygwin/13/include/stdatomic.h


However, clang delegates to system provided <stdatomic.h> if available, so
including <stdatomic.h> before other headers causes syntax errors.


$ echo '#include <stdatomic.h>' | clang -xc - -fsyntax-only
In file included from <stdin>:1:
In file included from /usr/lib/clang/21/include/stdatomic.h:24:
/usr/include/stdatomic.h:207:17: error: unknown type name 'int_least8_t'; 
did you mean '__int_least8_t'?
   207 | typedef _Atomic(int_least8_t)           atomic_int_least8_t;
       |                 ^
/usr/include/machine/_default_types.h:134:29: note: '__int_least8_t' 
declared here
   134 | typedef __INT_LEAST8_TYPE__ __int_least8_t;
       |                             ^
(snip)


$ echo '#include <stdatomic.h>' | clang -xc - -fsyntax-only  -H
. /usr/lib/clang/21/include/stdatomic.h
.. /usr/include/stdatomic.h
(snip)

$ echo '#include <stdatomic.h>' | clang -xc - -fsyntax-only -include 
stdint.h


Could it be fixed to make /usr/include/stdatomic.h self-contained?

--
Tomohiro Kashiwada (@kikairoya)


-- 
Problem reports:      https://cygwin.com/problems.html
FAQ:                  https://cygwin.com/faq/
Documentation:        https://cygwin.com/docs.html
Unsubscribe info:     https://cygwin.com/ml/#unsubscribe-simple