osdep: set _FORTIFY_SOURCE=2 when optimization is enabled

Currently we set _FORTIFY_SOURCE=2 as a compiler argument when the
meson 'optimization' setting is non-zero, the compiler is GCC and
the target is Linux.

While the default QEMU optimization level is 2, user could override
this by setting CFLAGS="-O0" or --extra-cflags="-O0" when running
configure and this won't be reflected in the meson 'optimization'
setting. As a result we try to enable _FORTIFY_SOURCE=2 and then the
user gets compile errors as it only works with optimization.

Rather than trying to improve detection in meson, it is simpler to
just check the __OPTIMIZE__ define from osdep.h.

The comment about being incompatible with clang appears to be
outdated, as compilation works fine without excluding clang.

In the coroutine code we must set _FORTIFY_SOURCE=0 to stop the
logic in osdep.h then enabling it.

Signed-off-by: Daniel P. Berrangé <berrange@redhat.com>
Message-id: 20231003091549.223020-1-berrange@redhat.com
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>

1 files changed, 4 insertions, 0 deletions

diff --git a/include/qemu/osdep.h b/include/qemu/osdep.h
index 18b940db75..475a1c62ff 100644
--- a/include/qemu/osdep.h
+++ b/include/qemu/osdep.h
@@ -27,6 +27,10 @@
 #ifndef QEMU_OSDEP_H
 #define QEMU_OSDEP_H
 
+#if !defined _FORTIFY_SOURCE && defined __OPTIMIZE__ && __OPTIMIZE__ && defined __linux__
+# define _FORTIFY_SOURCE 2
+#endif
+
 #include "config-host.h"
 #ifdef NEED_CPU_H
 #include CONFIG_TARGET