build without -fno-strict-aliasing when gcc isn't buggy #3326
Patch from Daniel Stutzbach
diff --git a/configure b/configure
index 3f74610..fa63d5f 100755
--- a/configure
+++ b/configure
@@ -1,5 +1,5 @@
#! /bin/sh
-# From configure.in Revision: 78965 .
+# From configure.in Revision: 79401 .
# Guess values for system-dependent variables and create Makefiles.
# Generated by GNU Autoconf 2.61 for python 3.2.
#
@@ -4569,14 +4569,16 @@
# tweak BASECFLAGS based on compiler and platform
case $GCC in
yes)
- # Python violates C99 rules, by casting between incompatible
- # pointer types. GCC may generate bad code as a result of that,
- # so use -fno-strict-aliasing if supported.
- { echo "$as_me:$LINENO: checking whether $CC accepts -fno-strict-aliasing" >&5
-echo $ECHO_N "checking whether $CC accepts -fno-strict-aliasing... $ECHO_C" >&6; }
+ # Python doesn't violate C99 aliasing rules, but older versions of
+ # GCC produce warnings for legal Python code. Enable
+ # -fno-strict-aliasing on versions of GCC that support but produce
+ # warnings. See Issue3326
+ { echo "$as_me:$LINENO: checking whether $CC accepts and needs -fno-strict-aliasing" >&5
+echo $ECHO_N "checking whether $CC accepts and needs -fno-strict-aliasing... $ECHO_C" >&6; }
ac_save_cc="$CC"
CC="$CC -fno-strict-aliasing"
- if test "${ac_cv_no_strict_aliasing_ok+set}" = set; then
+ save_CFLAGS="$CFLAGS"
+ if test "${ac_cv_no_strict_aliasing+set}" = set; then
echo $ECHO_N "(cached) $ECHO_C" >&6
else
cat >conftest.$ac_ext <<_ACEOF
@@ -4611,21 +4613,64 @@
test -z "$ac_c_werror_flag" ||
test ! -s conftest.err
} && test -s conftest.$ac_objext; then
- ac_cv_no_strict_aliasing_ok=yes
+ CC="$ac_save_cc -fstrict-aliasing"
+ CFLAGS="$CFLAGS -Werror -Wstrict-aliasing"
+ cat >conftest.$ac_ext <<_ACEOF
+/* confdefs.h. */
+_ACEOF
+cat confdefs.h >>conftest.$ac_ext
+cat >>conftest.$ac_ext <<_ACEOF
+/* end confdefs.h. */
+
+int
+main ()
+{
+void f(int **x) {} int main() { double *x; f((int **) &x); return 0; }
+ ;
+ return 0;
+}
+_ACEOF
+rm -f conftest.$ac_objext
+if { (ac_try="$ac_compile"
+case "(($ac_try" in
+ *\"* | *\`* | *\\*) ac_try_echo=\$ac_try;;
+ *) ac_try_echo=$ac_try;;
+esac
+eval "echo \"\$as_me:$LINENO: $ac_try_echo\"") >&5
+ (eval "$ac_compile") 2>conftest.er1
+ ac_status=$?
+ grep -v '^ *+' conftest.er1 >conftest.err
+ rm -f conftest.er1
+ cat conftest.err >&5
+ echo "$as_me:$LINENO: \$? = $ac_status" >&5
+ (exit $ac_status); } && {
+ test -z "$ac_c_werror_flag" ||
+ test ! -s conftest.err
+ } && test -s conftest.$ac_objext; then
+ ac_cv_no_strict_aliasing=no
else
echo "$as_me: failed program was:" >&5
sed 's/^/| /' conftest.$ac_ext >&5
- ac_cv_no_strict_aliasing_ok=no
+ ac_cv_no_strict_aliasing=yes
+fi
+
+rm -f core conftest.err conftest.$ac_objext conftest.$ac_ext
+else
+ echo "$as_me: failed program was:" >&5
+sed 's/^/| /' conftest.$ac_ext >&5
+
+ ac_cv_no_strict_aliasing=no
fi
rm -f core conftest.err conftest.$ac_objext conftest.$ac_ext
fi
+ CFLAGS="$save_CFLAGS"
CC="$ac_save_cc"
- { echo "$as_me:$LINENO: result: $ac_cv_no_strict_aliasing_ok" >&5
-echo "${ECHO_T}$ac_cv_no_strict_aliasing_ok" >&6; }
- if test $ac_cv_no_strict_aliasing_ok = yes
+ { echo "$as_me:$LINENO: result: $ac_cv_no_strict_aliasing" >&5
+echo "${ECHO_T}$ac_cv_no_strict_aliasing" >&6; }
+ if test $ac_cv_no_strict_aliasing = yes
then
BASECFLAGS="$BASECFLAGS -fno-strict-aliasing"
fi