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From: Stefan Weil <sw@weilnetz.de>
To: qemu-devel <qemu-devel@nongnu.org>
Cc: qemu-trivial <qemu-trivial@nongnu.org>,
	Stefan Weil <sw@weilnetz.de>, Jan Kiszka <jan.kiszka@web.de>,
	Anthony Liguori <anthony@codemonkey.ws>
Subject: [Qemu-trivial] [PATCH] cpu-exec: Fix compiler warning (-Werror=clobbered)
Date: Tue, 17 Sep 2013 19:03:22 +0200	[thread overview]
Message-ID: <1379437402-30804-1-git-send-email-sw@weilnetz.de> (raw)

'cpu' and 'env' are not modified after sigsetjmp. Therefore they will
still have their last value after longjmp restored the stack context.

The code which should "reload" both variables causes a compiler warning:

cpu-exec.c:204:15: error:
variable ‘cpu’ might be clobbered by ‘longjmp’ or ‘vfork’ [-Werror=clobbered]
cpu-exec.c:202:28: error:
argument ‘env’ might be clobbered by ‘longjmp’ or ‘vfork’ [-Werror=clobbered]

Remove this unneeded code.

Signed-off-by: Stefan Weil <sw@weilnetz.de>
---

Jan,

could you please review this patch which removes code added by you earlier?
I have run tests with the old code and assertions to see whether the values
were really smashed. They never were, and from the documentation of setjmp
I'd not expect that they ever might be.

The patch is needed to fix a compiler warning with -Wextra.

Thanks,
Stefan

 cpu-exec.c |    5 -----
 1 file changed, 5 deletions(-)

diff --git a/cpu-exec.c b/cpu-exec.c
index 5a43995..fbfb749 100644
--- a/cpu-exec.c
+++ b/cpu-exec.c
@@ -676,11 +676,6 @@ int cpu_exec(CPUArchState *env)
                 /* reset soft MMU for next block (it can currently
                    only be set by a memory fault) */
             } /* for(;;) */
-        } else {
-            /* Reload env after longjmp - the compiler may have smashed all
-             * local variables as longjmp is marked 'noreturn'. */
-            cpu = current_cpu;
-            env = cpu->env_ptr;
         }
     } /* for(;;) */
 
-- 
1.7.10.4



             reply	other threads:[~2013-09-17 17:03 UTC|newest]

Thread overview: 4+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2013-09-17 17:03 Stefan Weil [this message]
2013-09-17 17:17 ` [Qemu-trivial] [PATCH] cpu-exec: Fix compiler warning (-Werror=clobbered) Jan Kiszka
2013-09-17 17:27   ` Stefan Weil
2013-09-17 21:24 ` [Qemu-trivial] [Qemu-devel] " Peter Maydell

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