[Qemu-devel] [PATCH v4] configure: properly check if -lrt and -lm is needed

[Natanael Copa]

Fixes build against uClibc.

uClibc provides 2 versions of clock_gettime(), one with realtime
support and one without (this is so you can avoid linking in -lrt
unless actually needed). This means that the clock_gettime() don't
need -lrt. We still need it for timer_create() so we check for this
function in addition.

We also need check if -lm is needed for isnan().

Both -lm and -lrt are needed for libs_qga.

Signed-off-by: Natanael Copa <address@hidden>
---
Changes v3->v4:
 - Use $pthread_lib from previous pthread test
   We don't need to add it to $LIBS since it should be there already

 configure | 36 ++++++++++++++++++++++++++++++++++--
 1 file changed, 34 insertions(+), 2 deletions(-)

diff --git a/configure b/configure
index edf9da4..31eee91 100755
--- a/configure
+++ b/configure
@@ -2624,17 +2624,49 @@ fi
 
 
 ##########################################
+# Do we need libm
+cat > $TMPC << EOF
+#include <math.h>
+int main(void) { return isnan(sin(0.0)); }
+EOF
+if compile_prog "" "" ; then
+  :
+elif compile_prog "" "-lm" ; then
+  LIBS="-lm $LIBS"
+  libs_qga="-lm $libs_qga"
+else
+  echo
+  echo "Error: libm check failed"
+  echo
+  exit 1
+fi
+
+##########################################
 # Do we need librt
+# uClibc provides 2 versions of clock_gettime(), one with realtime
+# support and one without. This means that the clock_gettime() don't
+# need -lrt. We still need it for timer_create() so we check for this
+# function in addition.
 cat > $TMPC <<EOF
 #include <signal.h>
 #include <time.h>
-int main(void) { return clock_gettime(CLOCK_REALTIME, NULL); }
+int main(void) {
+  timer_create(CLOCK_REALTIME, NULL, NULL);
+  return clock_gettime(CLOCK_REALTIME, NULL);
+}
 EOF
 
 if compile_prog "" "" ; then
   :
-elif compile_prog "" "-lrt" ; then
+# we need pthread for static linking. use previous pthread test result 
+elif compile_prog "" "-lrt $pthread_lib" ; then
   LIBS="-lrt $LIBS"
+  libs_qga="-lrt $libs_qga"
+else
+  echo
+  echo "Error: librt check failed"
+  echo
+  exit 1
 fi
 
 if test "$darwin" != "yes" -a "$mingw32" != "yes" -a "$solaris" != yes -a \
-- 
1.7.12