emacs-28 6d9b3c0: Port systhreads.h to C2x

[Paul Eggert]

branch: emacs-28
commit 6d9b3c0eaab2d553b2fea127f2f2b9fa44f44450
Author: Paul Eggert <eggert@cs.ucla.edu>
Commit: Paul Eggert <eggert@cs.ucla.edu>

    Port systhreads.h to C2x
    
    * src/systhread.h: Put NODISCARD at the start of extern
    declarations, not at the end.  This is needed by C2x.
    This patch also pacifies gcc 11.2.1 -Wattributes.
---
 src/systhread.h | 13 +++++--------
 1 file changed, 5 insertions(+), 8 deletions(-)

diff --git a/src/systhread.h b/src/systhread.h
index 0f47d7c..601505f 100644
--- a/src/systhread.h
+++ b/src/systhread.h
@@ -101,14 +101,11 @@ extern void sys_cond_signal (sys_cond_t *);
 extern void sys_cond_broadcast (sys_cond_t *);
 extern void sys_cond_destroy (sys_cond_t *);
 
-extern sys_thread_t sys_thread_self (void)
-  NODISCARD;
-extern bool sys_thread_equal (sys_thread_t, sys_thread_t)
-  NODISCARD;
-
-extern bool sys_thread_create (sys_thread_t *, thread_creation_function *,
-                               void *)
-  NODISCARD;
+NODISCARD extern sys_thread_t sys_thread_self (void);
+NODISCARD extern bool sys_thread_equal (sys_thread_t, sys_thread_t);
+
+NODISCARD extern bool sys_thread_create (sys_thread_t *,
+                                        thread_creation_function *, void *);
 
 extern void sys_thread_yield (void);
 extern void sys_thread_set_name (const char *);