[patch] Prevent secondary warning from diagnostic tweak in gthr-vxworks.h

[patch] Prevent secondary warning from diagnostic tweak in gthr-vxworks.h

[Olivier Hainque]

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Within gthr-vxworks.h, we prevent C++ errors from missing
declarations in some system headers by prepending their inclusion
with a

    #pragma GCC diagnostic ignored "-Wstrict-prototypes"

But Wstrict-prototypes is internally registered as valid for
C/ObjC only, not C++, and this trick in turn triggers a Wpragma
warning with -Wsystem-headers.

This change just arranges to ignore the secondary warning locally.

We have been using this for a while with gcc-11 based toolchains,
where the only effect was the intended disappearance of a test failure
observed on g++.dg/warn/Wstringop-overflow-6.C.

Sanity checked with a build + basic testing with a gcc-12
compiler, then a mainline build for arm-vxworks7r2.

Cheers

Olivier

2021-02-03  Olivier Hainque  <hainque@adacore.com>

        * config/gthr-vxworks.h: Prevent Wpragma warning for the
        pragma diagnostics on Wstrict-prototypes.


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From 97e4ee1d69a350e8e4bac25265e27f207baf2850 Mon Sep 17 00:00:00 2001
From: Olivier Hainque <hainque@adacore.com>
Date: Thu, 3 Feb 2022 15:57:32 +0000
Subject: [PATCH 10/18] Prevent secondary warning from diagnostic tweak in
 gthr-vxworks.h

Within gthr-vxworks.h, we prevent C++ errors from missing
declarations in some system headers by prepending their inclusion
with a

    #pragma GCC diagnostic ignored "-Wstrict-prototypes"

But Wstrict-prototypes is internally registered as valid for
C/ObjC only, not C++, and this trick in turn triggers a Wpragma
warning with -Wsystem-headers.

This change just arranges to ignore the secondary warning locally.

2021-02-03  Olivier Hainque  <hainque@adacore.com>

	* config/gthr-vxworks.h: Prevent Wpragma warning for the
	pragma diagnostics on Wstrict-prototypes.
---
 libgcc/config/gthr-vxworks.h | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

diff --git a/libgcc/config/gthr-vxworks.h b/libgcc/config/gthr-vxworks.h
index 9861a11511a..31c4b9f2557 100644
--- a/libgcc/config/gthr-vxworks.h
+++ b/libgcc/config/gthr-vxworks.h
@@ -38,8 +38,11 @@ see the files COPYING3 and COPYING.RUNTIME respectively.  If not, see
 #include <_vxworks-versions.h>
 
 /* Some VxWorks headers profusely use typedefs of a pointer to a function with
-   undefined number of arguments.  */
+   undefined number of arguments.  Arrange to ignore declaration errors in C++,
+   which is achievable by ignoring Wstrict-prototypes diagnostics even when the
+   option is registered as only valid for c/objc.  */
 #pragma GCC diagnostic push
+  #pragma GCC diagnostic ignored "-Wpragmas"
   #pragma GCC diagnostic ignored "-Wstrict-prototypes"
   #include <semLib.h>
 #pragma GCC diagnostic pop
-- 
2.25.1


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