[Qemu-devel] [PATCHv2] configure: use correct cflags in compiler checks

[Qemu-devel] [PATCHv2] configure: use correct cflags in compiler checks

[Michael S. Tsirkin]

linux-user build on fedora 11 breaks because fallocate
is broken on that system if -D_GNU_SOURCE -D_FILE_OFFSET_BITS=64
are specified, which is what QEMU uses.

We do have a configure check to catch this and disable fallocate,
however, it turns out that default QEMU_CFLAGS/LDFLAGS were assigned in
script *after* all compiler checks: so during checks we were not running
compiler with same flags that we used for build later.

Fix this by moving QEMU_CFLAGS to before compiler checks, and using
comple_prog when checking for fallocate.  This also fixes the fact that
we do some compiler checks while assigning the flags, right below a
comment that says "no cc tests beyond this point".

Move a couple of left-over checks to compile_prog so that
this applies to them.

Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
---

Changes from v1:
	kill ARCH_CFLAGS and update dup test as well

 configure |   43 ++++++++++++++++++++++---------------------
 1 files changed, 22 insertions(+), 21 deletions(-)

diff --git a/configure b/configure
index fb66246..0b69b4f 100755
--- a/configure
+++ b/configure
@@ -91,6 +91,26 @@ ar="${cross_prefix}${ar}"
 objcopy="${cross_prefix}${objcopy}"
 ld="${cross_prefix}${ld}"
 
+# default flags for all hosts
+QEMU_CFLAGS="-fno-strict-aliasing $QEMU_CFLAGS"
+CFLAGS="-g $CFLAGS"
+QEMU_CFLAGS="-Wall -Wundef -Wendif-labels -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"
+QEMU_CFLAGS="-U_FORTIFY_SOURCE $QEMU_CFLAGS"
+QEMU_CFLAGS="-I. -I\$(SRC_PATH) $QEMU_CFLAGS"
+LDFLAGS="-g $LDFLAGS"
+
+gcc_flags="-Wold-style-declaration -Wold-style-definition"
+cat > $TMPC << EOF
+int main(void) { }
+EOF
+for flag in $gcc_flags; do
+    if compile_prog "$QEMU_CFLAGS" "$flag" ; then
+	QEMU_CFLAGS="$flag $QEMU_CFLAGS"
+    fi
+done
+
 # check that the C compiler works.
 cat > $TMPC <<EOF
 int main(void) {}
@@ -1585,7 +1605,7 @@ int main(void)
     return 0;
 }
 EOF
-if $cc $ARCH_CFLAGS -o $TMPE $TMPC 2> /dev/null ; then
+if compile_prog "" "" ; then
   fallocate=yes
 fi
 
@@ -1600,7 +1620,7 @@ int main(void)
     return 0;
 }
 EOF
-if $cc $ARCH_CFLAGS -o $TMPE $TMPC 2> /dev/null ; then
+if compile_prog "" "" ; then
   dup3=yes
 fi
 
@@ -1733,28 +1753,9 @@ fi
 # End of CC checks
 # After here, no more $cc or $ld runs
 
-# default flags for all hosts
-QEMU_CFLAGS="-fno-strict-aliasing $QEMU_CFLAGS"
-CFLAGS="-g $CFLAGS"
 if test "$debug" = "no" ; then
   CFLAGS="-O2 $CFLAGS"
 fi
-QEMU_CFLAGS="-Wall -Wundef -Wendif-labels -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"
-QEMU_CFLAGS="-U_FORTIFY_SOURCE $QEMU_CFLAGS"
-QEMU_CFLAGS="-I. -I\$(SRC_PATH) $QEMU_CFLAGS"
-LDFLAGS="-g $LDFLAGS"
-
-gcc_flags="-Wold-style-declaration -Wold-style-definition"
-cat > $TMPC << EOF
-int main(void) { }
-EOF
-for flag in $gcc_flags; do
-    if compile_prog "$QEMU_CFLAGS" "$flag" ; then
-	QEMU_CFLAGS="$flag $QEMU_CFLAGS"
-    fi
-done
 
 # Consult white-list to determine whether to enable werror
 # by default.  Only enable by default for git builds
-- 
1.6.5.2.143.g8cc62