only use -fno-strict-aliasing when needed by compiler
diff --git a/configure b/configure
index 2eb16b9..d7cffff 100755
--- a/configure
+++ b/configure
@@ -5295,33 +5295,72 @@
# 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.
- { $as_echo "$as_me:${as_lineno-$LINENO}: checking whether $CC accepts -fno-strict-aliasing" >&5
-$as_echo_n "checking whether $CC accepts -fno-strict-aliasing... " >&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
+ { $as_echo "$as_me:${as_lineno-$LINENO}: checking whether $CC accepts and needs -fno-strict-aliasing" >&5
+$as_echo_n "checking whether $CC accepts and needs -fno-strict-aliasing... " >&6; }
ac_save_cc="$CC"
CC="$CC -fno-strict-aliasing"
- if test "$cross_compiling" = yes; then :
- ac_cv_no_strict_aliasing_ok=no
+ save_CFLAGS="$CFLAGS"
+ if test "${ac_cv_no_strict_aliasing+set}" = set; then :
+ $as_echo_n "(cached) " >&6
else
cat confdefs.h - <<_ACEOF >conftest.$ac_ext
/* end confdefs.h. */
-int main() { return 0; }
+
+
+int
+main ()
+{
+
+ ;
+ return 0;
+}
+
_ACEOF
-if ac_fn_c_try_run "$LINENO"; then :
- ac_cv_no_strict_aliasing_ok=yes
+if ac_fn_c_try_compile "$LINENO"; then :
+
+ CC="$ac_save_cc -fstrict-aliasing"
+ CFLAGS="$CFLAGS -Werror -Wstrict-aliasing"
+ cat confdefs.h - <<_ACEOF >conftest.$ac_ext
+/* end confdefs.h. */
+
+ void f(int **x) {}
+int
+main ()
+{
+double *x; f((int **) &x);
+ ;
+ return 0;
+}
+
+_ACEOF
+if ac_fn_c_try_compile "$LINENO"; then :
+
+ ac_cv_no_strict_aliasing=no
+
else
- ac_cv_no_strict_aliasing_ok=no
+
+ ac_cv_no_strict_aliasing=yes
+
fi
-rm -f core *.core core.conftest.* gmon.out bb.out conftest$ac_exeext \
- conftest.$ac_objext conftest.beam conftest.$ac_ext
+rm -f core conftest.err conftest.$ac_objext conftest.$ac_ext
+
+else
+
+ ac_cv_no_strict_aliasing=no
+
+fi
+rm -f core conftest.err conftest.$ac_objext conftest.$ac_ext
fi
+ CFLAGS="$save_CFLAGS"
CC="$ac_save_cc"
- { $as_echo "$as_me:${as_lineno-$LINENO}: result: $ac_cv_no_strict_aliasing_ok" >&5
-$as_echo "$ac_cv_no_strict_aliasing_ok" >&6; }
- if test $ac_cv_no_strict_aliasing_ok = yes
+ { $as_echo "$as_me:${as_lineno-$LINENO}: result: $ac_cv_no_strict_aliasing" >&5
+$as_echo "$ac_cv_no_strict_aliasing" >&6; }
+ if test $ac_cv_no_strict_aliasing = yes
then
BASECFLAGS="$BASECFLAGS -fno-strict-aliasing"
fi