Commit f80ea986 authored by Alexey Kardashevskiy's avatar Alexey Kardashevskiy Committed by Paolo Bonzini
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configure: Fix -lm test, so that tools can be compiled on hosts that require -lm 



The existing test whether "-lm" needs to be included or not is
insufficient as it reports false negative on Fedora20/ppc64.
This happens because sin(0.0) is a constant value which compiler
can safely throw away and therefore there is no need to add "-lm".
As the result, qemu-nbd/qemu-io/qemu-img tools cannot compile.

This adds a global variable and uses it in the test to prevent
from optimization.

Signed-off-by: default avatarAlexey Kardashevskiy <aik@ozlabs.ru>
[Use Peter's improvement on the test to fool LTO, and remove the
 now useless -lm addition in Makefile.target. - Paolo]
Signed-off-by: default avatarPaolo Bonzini <pbonzini@redhat.com>
parent 424baff5

Makefile.target

+0 −4
Original line number Diff line number Diff line
@@ -163,10 +163,6 @@ dummy := $(call unnest-vars,.., \ 
all-obj-y += $(common-obj-y)

all-obj-$(CONFIG_SOFTMMU) += $(block-obj-y)



ifndef CONFIG_HAIKU

LIBS+=-lm

endif



# build either PROG or PROGW

$(QEMU_PROG_BUILD): $(all-obj-y) ../libqemuutil.a ../libqemustub.a

	$(call LINK,$^)

configure

+1 −1
Original line number Diff line number Diff line
@@ -3453,7 +3453,7 @@ fi 
# Do we need libm

cat > $TMPC << EOF

#include <math.h>

int main(void) { return isnan(sin(0.0)); }

int main(int argc, char **argv) { return isnan(sin((double)argc)); }

EOF

if compile_prog "" "" ; then

  :