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build without -fno-strict-aliasing when gcc isn't buggy #3326
Patch from Daniel Stutzbach
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parent
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commit
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@ -883,6 +883,9 @@ Extension Modules
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Build
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-----
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- Issue #3326: Build Python without -fno-strict-aliasing when the gcc does not
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give false warnings.
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- Issue #1628484: The Makefile doesn't ignore the CFLAGS environment
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variable anymore. It also forwards the LDFLAGS settings to the linker
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when building a shared library.
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69
configure
vendored
69
configure
vendored
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@ -1,5 +1,5 @@
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#! /bin/sh
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# From configure.in Revision: 78965 .
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# From configure.in Revision: 79401 .
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# Guess values for system-dependent variables and create Makefiles.
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# Generated by GNU Autoconf 2.61 for python 3.2.
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#
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@ -4569,14 +4569,16 @@ UNIVERSAL_ARCH_FLAGS=
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# tweak BASECFLAGS based on compiler and platform
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case $GCC in
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yes)
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# Python violates C99 rules, by casting between incompatible
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# pointer types. GCC may generate bad code as a result of that,
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# so use -fno-strict-aliasing if supported.
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{ echo "$as_me:$LINENO: checking whether $CC accepts -fno-strict-aliasing" >&5
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echo $ECHO_N "checking whether $CC accepts -fno-strict-aliasing... $ECHO_C" >&6; }
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# Python doesn't violate C99 aliasing rules, but older versions of
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# GCC produce warnings for legal Python code. Enable
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# -fno-strict-aliasing on versions of GCC that support but produce
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# warnings. See Issue3326
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{ echo "$as_me:$LINENO: checking whether $CC accepts and needs -fno-strict-aliasing" >&5
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echo $ECHO_N "checking whether $CC accepts and needs -fno-strict-aliasing... $ECHO_C" >&6; }
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ac_save_cc="$CC"
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CC="$CC -fno-strict-aliasing"
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if test "${ac_cv_no_strict_aliasing_ok+set}" = set; then
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save_CFLAGS="$CFLAGS"
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if test "${ac_cv_no_strict_aliasing+set}" = set; then
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echo $ECHO_N "(cached) $ECHO_C" >&6
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else
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cat >conftest.$ac_ext <<_ACEOF
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@ -4611,21 +4613,64 @@ eval "echo \"\$as_me:$LINENO: $ac_try_echo\"") >&5
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test -z "$ac_c_werror_flag" ||
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test ! -s conftest.err
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} && test -s conftest.$ac_objext; then
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ac_cv_no_strict_aliasing_ok=yes
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CC="$ac_save_cc -fstrict-aliasing"
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CFLAGS="$CFLAGS -Werror -Wstrict-aliasing"
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cat >conftest.$ac_ext <<_ACEOF
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/* confdefs.h. */
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_ACEOF
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cat confdefs.h >>conftest.$ac_ext
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cat >>conftest.$ac_ext <<_ACEOF
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/* end confdefs.h. */
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int
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main ()
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{
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void f(int **x) {} int main() { double *x; f((int **) &x); return 0; }
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;
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return 0;
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}
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_ACEOF
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rm -f conftest.$ac_objext
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if { (ac_try="$ac_compile"
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case "(($ac_try" in
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*\"* | *\`* | *\\*) ac_try_echo=\$ac_try;;
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*) ac_try_echo=$ac_try;;
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esac
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eval "echo \"\$as_me:$LINENO: $ac_try_echo\"") >&5
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(eval "$ac_compile") 2>conftest.er1
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ac_status=$?
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grep -v '^ *+' conftest.er1 >conftest.err
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rm -f conftest.er1
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cat conftest.err >&5
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echo "$as_me:$LINENO: \$? = $ac_status" >&5
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(exit $ac_status); } && {
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test -z "$ac_c_werror_flag" ||
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test ! -s conftest.err
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} && test -s conftest.$ac_objext; then
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ac_cv_no_strict_aliasing=no
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else
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echo "$as_me: failed program was:" >&5
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sed 's/^/| /' conftest.$ac_ext >&5
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ac_cv_no_strict_aliasing_ok=no
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ac_cv_no_strict_aliasing=yes
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fi
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rm -f core conftest.err conftest.$ac_objext conftest.$ac_ext
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else
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echo "$as_me: failed program was:" >&5
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sed 's/^/| /' conftest.$ac_ext >&5
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ac_cv_no_strict_aliasing=no
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fi
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rm -f core conftest.err conftest.$ac_objext conftest.$ac_ext
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fi
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CFLAGS="$save_CFLAGS"
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CC="$ac_save_cc"
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{ echo "$as_me:$LINENO: result: $ac_cv_no_strict_aliasing_ok" >&5
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echo "${ECHO_T}$ac_cv_no_strict_aliasing_ok" >&6; }
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if test $ac_cv_no_strict_aliasing_ok = yes
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{ echo "$as_me:$LINENO: result: $ac_cv_no_strict_aliasing" >&5
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echo "${ECHO_T}$ac_cv_no_strict_aliasing" >&6; }
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if test $ac_cv_no_strict_aliasing = yes
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then
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BASECFLAGS="$BASECFLAGS -fno-strict-aliasing"
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fi
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27
configure.in
27
configure.in
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@ -867,19 +867,26 @@ AC_SUBST(UNIVERSAL_ARCH_FLAGS)
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# tweak BASECFLAGS based on compiler and platform
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case $GCC in
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yes)
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# Python violates C99 rules, by casting between incompatible
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# pointer types. GCC may generate bad code as a result of that,
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# so use -fno-strict-aliasing if supported.
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AC_MSG_CHECKING(whether $CC accepts -fno-strict-aliasing)
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# Python doesn't violate C99 aliasing rules, but older versions of
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# GCC produce warnings for legal Python code. Enable
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# -fno-strict-aliasing on versions of GCC that support but produce
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# warnings. See Issue3326
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AC_MSG_CHECKING(whether $CC accepts and needs -fno-strict-aliasing)
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ac_save_cc="$CC"
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CC="$CC -fno-strict-aliasing"
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AC_CACHE_VAL(ac_cv_no_strict_aliasing_ok,
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AC_TRY_COMPILE([],[int main() { return 0; }],
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ac_cv_no_strict_aliasing_ok=yes,
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ac_cv_no_strict_aliasing_ok=no))
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save_CFLAGS="$CFLAGS"
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AC_CACHE_VAL(ac_cv_no_strict_aliasing,
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AC_TRY_COMPILE([],[int main() { return 0; }],
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CC="$ac_save_cc -fstrict-aliasing"
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CFLAGS="$CFLAGS -Werror -Wstrict-aliasing"
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AC_TRY_COMPILE([],[void f(int **x) {} int main() { double *x; f((int **) &x); return 0; }],
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ac_cv_no_strict_aliasing=no,
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ac_cv_no_strict_aliasing=yes),
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ac_cv_no_strict_aliasing=no))
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CFLAGS="$save_CFLAGS"
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CC="$ac_save_cc"
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AC_MSG_RESULT($ac_cv_no_strict_aliasing_ok)
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if test $ac_cv_no_strict_aliasing_ok = yes
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AC_MSG_RESULT($ac_cv_no_strict_aliasing)
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if test $ac_cv_no_strict_aliasing = yes
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then
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BASECFLAGS="$BASECFLAGS -fno-strict-aliasing"
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fi
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