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[fix,for,2.1,v2] makefile: Fix tools compile

Message ID 1404199827-7823-1-git-send-email-aik@ozlabs.ru
State New
Headers show

Commit Message

Alexey Kardashevskiy July 1, 2014, 7:30 a.m. UTC 
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(-)
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Patch

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
   :