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[Qemu-devel] [PULL 10/14] cpu-exec: Fix compiler warning (-Werror=clobbe
From: |
Paolo Bonzini |
Subject: |
[Qemu-devel] [PULL 10/14] cpu-exec: Fix compiler warning (-Werror=clobbered) |
Date: |
Wed, 4 Nov 2015 17:18:28 +0100 |
From: Stefan Weil <address@hidden>
Reloading of local variables after sigsetjmp is only needed for some
buggy compilers.
The code which should reload these variables causes compiler warnings
with gcc 4.7 when compiler optimizations are enabled:
cpu-exec.c:204:15: error:
variable ‘cpu’ might be clobbered by ‘longjmp’ or ‘vfork’ [-Werror=clobbered]
cpu-exec.c:207:15: error:
variable ‘cc’ 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]
Now this code is only used for compilers which need it
(and gcc 4.5.x, x > 0 which does not need it but won't give warnings).
There were bug reports for clang and gcc 4.5.0, while gcc 4.5.1
was reported to work fine without the reload code. For clang it
is not clear which versions are affected, so simply keep the status quo
for all clang compilations. This can be improved later.
Signed-off-by: Stefan Weil <address@hidden>
Message-Id: <address@hidden>
Signed-off-by: Paolo Bonzini <address@hidden>
---
cpu-exec.c | 18 +++++++++++++++---
1 file changed, 15 insertions(+), 3 deletions(-)
diff --git a/cpu-exec.c b/cpu-exec.c
index 7eef083..2cfb3d0 100644
--- a/cpu-exec.c
+++ b/cpu-exec.c
@@ -539,15 +539,27 @@ int cpu_exec(CPUState *cpu)
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'. */
+#if defined(__clang__) || !QEMU_GNUC_PREREQ(4, 6)
+ /* Some compilers wrongly smash all local variables after
+ * siglongjmp. There were bug reports for gcc 4.5.0 and clang.
+ * Reload essential local variables here for those compilers.
+ * Newer versions of gcc would complain about this code
(-Wclobbered). */
cpu = current_cpu;
cc = CPU_GET_CLASS(cpu);
- cpu->can_do_io = 1;
#ifdef TARGET_I386
x86_cpu = X86_CPU(cpu);
env = &x86_cpu->env;
#endif
+#else /* buggy compiler */
+ /* Assert that the compiler does not smash local variables. */
+ g_assert(cpu == current_cpu);
+ g_assert(cc == CPU_GET_CLASS(cpu));
+#ifdef TARGET_I386
+ g_assert(x86_cpu == X86_CPU(cpu));
+ g_assert(env == &x86_cpu->env);
+#endif
+#endif /* buggy compiler */
+ cpu->can_do_io = 1;
tb_lock_reset();
}
} /* for(;;) */
--
1.8.3.1
- [Qemu-devel] [PULL 00/14] Misc changes for QEMU 2.4-rc1, Paolo Bonzini, 2015/11/04
- [Qemu-devel] [PULL 02/14] scripts/text2pod.pl: Escape left brace, Paolo Bonzini, 2015/11/04
- [Qemu-devel] [PULL 05/14] qemu-log: remove -d ioport, Paolo Bonzini, 2015/11/04
- [Qemu-devel] [PULL 01/14] file_ram_alloc: propagate error to caller instead of terminating QEMU, Paolo Bonzini, 2015/11/04
- [Qemu-devel] [PULL 04/14] ioport: do not use CPU_LOG_IOPORT, Paolo Bonzini, 2015/11/04
- [Qemu-devel] [PULL 03/14] target-i386: fix pcmpxstrx equal-ordered (strstr) mode, Paolo Bonzini, 2015/11/04
- [Qemu-devel] [PULL 10/14] cpu-exec: Fix compiler warning (-Werror=clobbered),
Paolo Bonzini <=
- [Qemu-devel] [PULL 06/14] pc: Set hw_version on all machine classes, Paolo Bonzini, 2015/11/04
- [Qemu-devel] [PULL 09/14] memory: call begin, log_start and commit when registering a new listener, Paolo Bonzini, 2015/11/04
- [Qemu-devel] [PULL 11/14] configure: disallow ccache during compile tests, Paolo Bonzini, 2015/11/04
- [Qemu-devel] [PULL 14/14] configure: disable FORTIFY_SOURCE under clang, Paolo Bonzini, 2015/11/04
- [Qemu-devel] [PULL 07/14] osdep: Rename qemu_{get, set}_version() to qemu_{, set_}hw_version(), Paolo Bonzini, 2015/11/04
- [Qemu-devel] [PULL 12/14] backends/hostmem-file: Allow to specify full pathname for backing file, Paolo Bonzini, 2015/11/04
- [Qemu-devel] [PULL 13/14] iscsi: Translate scsi sense into error code, Paolo Bonzini, 2015/11/04
- [Qemu-devel] [PULL 08/14] megasas: Use qemu_hw_version() instead of QEMU_VERSION, Paolo Bonzini, 2015/11/04
- Re: [Qemu-devel] [PULL 00/14] Misc changes for QEMU 2.4-rc1, Peter Maydell, 2015/11/04