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[Qemu-devel] [PATCH] configure: Always build with -fno-common
From: |
Peter Maydell |
Subject: |
[Qemu-devel] [PATCH] configure: Always build with -fno-common |
Date: |
Wed, 26 Feb 2014 21:53:30 +0000 |
MacOSX doesn't pull .o files from .a archives if the symbol that it
requires is one which the .o file defines as a common symbol.
(Common symbols are those declared without "extern"; the linker
will merge together common symbols with the same name, so
redeclaring the same variable in two compilation units results in
them referring to the same symbol rather than a compilation error).
This MacOSX difference from traditional linker behaviour means that
"make check" produces link errors:
Undefined symbols for architecture x86_64:
"_cur_mon", referenced from:
_error_vprintf in libqemuutil.a(qemu-error.o)
_error_printf in libqemuutil.a(qemu-error.o)
_error_printf_unless_qmp in libqemuutil.a(qemu-error.o)
_error_print_loc in libqemuutil.a(qemu-error.o)
_error_report in libqemuutil.a(qemu-error.o)
ld: symbol(s) not found for architecture x86_64
in this case because "cur_mon" is a common symbol in
libqemustub.a(mon-set-error.o).
In QEMU we don't make any use at all of the common symbol
functionality, so we can avoid this problem entirely simply
by compiling with -fno-common. Enable this option for all
builds, not just MacOSX, so that if we ever inadvertently
introduce multiple definitions of some variable that will
be immediately spotted as a build error rather than only
breaking the MacOSX build.
Suggested-by: Markus Armbruster <address@hidden>
Signed-off-by: Peter Maydell <address@hidden>
---
Thanks to Markus for pointing out that -fno-common was the
simple solution to this problem. make check now works on MacOSX,
although due to a race condition in the version of glib I'm stuck
on (2.22.4) I have to periodically use "killall -CHLD gtester"
to unwedge it...
configure | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/configure b/configure
index 423f435..ff438e4 100755
--- a/configure
+++ b/configure
@@ -369,7 +369,7 @@ sdl_config="${SDL_CONFIG-${cross_prefix}sdl-config}"
ARFLAGS="${ARFLAGS-rv}"
# default flags for all hosts
-QEMU_CFLAGS="-fno-strict-aliasing $QEMU_CFLAGS"
+QEMU_CFLAGS="-fno-strict-aliasing -fno-common $QEMU_CFLAGS"
QEMU_CFLAGS="-Wall -Wundef -Wwrite-strings -Wmissing-prototypes $QEMU_CFLAGS"
QEMU_CFLAGS="-Wstrict-prototypes -Wredundant-decls $QEMU_CFLAGS"
QEMU_CFLAGS="-D_GNU_SOURCE -D_FILE_OFFSET_BITS=64 -D_LARGEFILE_SOURCE
$QEMU_CFLAGS"
--
1.8.5.4
- [Qemu-devel] [PATCH] configure: Always build with -fno-common,
Peter Maydell <=