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build without -fno-strict-aliasing when gcc isn't buggy #3326

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Patch from Daniel Stutzbach
This commit is contained in:
Benjamin Peterson 2010-03-30 17:34:47 +00:00
parent fc91aa28fd
commit e6c9d24562
3 changed files with 77 additions and 22 deletions
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3
Misc/NEWS
View file

@ -883,6 +883,9 @@ Extension Modules
Build
-----
- Issue #3326: Build Python without -fno-strict-aliasing when the gcc does not
give false warnings.
- Issue #1628484: The Makefile doesn't ignore the CFLAGS environment
variable anymore. It also forwards the LDFLAGS settings to the linker
when building a shared library.

69
configure vendored
View file

@ -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 @@ UNIVERSAL_ARCH_FLAGS=
# 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 @@ eval "echo \"\$as_me:$LINENO: $ac_try_echo\"") >&5
test -z "$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

27
configure.in
View file

@ -867,19 +867,26 @@ AC_SUBST(UNIVERSAL_ARCH_FLAGS)
# 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.
AC_MSG_CHECKING(whether $CC accepts -fno-strict-aliasing)
# 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
AC_MSG_CHECKING(whether $CC accepts and needs -fno-strict-aliasing)
ac_save_cc="$CC"
CC="$CC -fno-strict-aliasing"
AC_CACHE_VAL(ac_cv_no_strict_aliasing_ok,
AC_TRY_COMPILE([],[int main() { return 0; }],
ac_cv_no_strict_aliasing_ok=yes,
ac_cv_no_strict_aliasing_ok=no))
save_CFLAGS="$CFLAGS"
AC_CACHE_VAL(ac_cv_no_strict_aliasing,
AC_TRY_COMPILE([],[int main() { return 0; }],
CC="$ac_save_cc -fstrict-aliasing"
CFLAGS="$CFLAGS -Werror -Wstrict-aliasing"
AC_TRY_COMPILE([],[void f(int **x) {} int main() { double *x; f((int **) &x); return 0; }],
ac_cv_no_strict_aliasing=no,
ac_cv_no_strict_aliasing=yes),
ac_cv_no_strict_aliasing=no))
CFLAGS="$save_CFLAGS"
CC="$ac_save_cc"
AC_MSG_RESULT($ac_cv_no_strict_aliasing_ok)
if test $ac_cv_no_strict_aliasing_ok = yes
AC_MSG_RESULT($ac_cv_no_strict_aliasing)
if test $ac_cv_no_strict_aliasing = yes
then
BASECFLAGS="$BASECFLAGS -fno-strict-aliasing"
fi