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Date: Tue, 01 Jul 2014 09:41:35 +0200
From: Paolo Bonzini <pbonzini@redhat.com>
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Subject: Re: [Qemu-devel] [PATCH fix for 2.1 v2] makefile: Fix tools compile
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To: Alexey Kardashevskiy <aik@ozlabs.ru>, qemu-devel@nongnu.org
Cc: Peter Maydell <peter.maydell@linaro.org>

Il 01/07/2014 09:30, Alexey Kardashevskiy ha scritto:
> 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: Alexey Kardashevskiy <aik@ozlabs.ru>
>
> ---
> Changes:
> v2:
> * previous s/sin/log/ replacement removed, a global variable is
> used instead
> ---
>  configure | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/configure b/configure
> index 23ecb37..6dd44a9 100755
> --- a/configure
> +++ b/configure
> @@ -3453,7 +3453,7 @@ fi
>  # Do we need libm
>  cat > $TMPC << EOF
>  #include <math.h>
> -int main(void) { return isnan(sin(0.0)); }
> +double x; int main(void) {return isnan(sin(x));}
>  EOF
>  if compile_prog "" "" ; then
>    :
>

Can you please test with this hunk on top:

diff --git a/Makefile.target b/Makefile.target
index 6089d29..137d0b0 100644
--- a/Makefile.target
+++ b/Makefile.target
@@ -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
  	$(call LINK,$^)

It should now be unnecessary.

Paolo