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| author | Victor Stinner <victor.stinner@gmail.com> | 2017-04-28 15:07:10 +0200 |
|---|---|---|
| committer | GitHub <noreply@github.com> | 2017-04-28 15:07:10 +0200 |
| commit | 826f83f1d562a7b878499bc3af2267cfdfe5f2f9 (patch) | |
| tree | d35096a04bd036d1e807309764002f40d4274f9e | |
| parent | 5a4e3d8f9c37e700402b23fafbfc413e5ca3113d (diff) | |
| download | cpython-git-826f83f1d562a7b878499bc3af2267cfdfe5f2f9.tar.gz | |
bpo-30104: Only use -fno-strict-aliasing on dtoa.c (#1340)
On clang, only compile dtoa.c with -fno-strict-aliasing, use strict
aliasing to compile all other C files.
| -rw-r--r-- | Makefile.pre.in | 9 | ||||
| -rwxr-xr-x | configure | 11 | ||||
| -rw-r--r-- | configure.ac | 13 |
3 files changed, 17 insertions, 16 deletions
diff --git a/Makefile.pre.in b/Makefile.pre.in index 4145634c03..e5141f11da 100644 --- a/Makefile.pre.in +++ b/Makefile.pre.in @@ -107,6 +107,8 @@ ARFLAGS= @ARFLAGS@ CFLAGSFORSHARED=@CFLAGSFORSHARED@ # C flags used for building the interpreter object files PY_CORE_CFLAGS= $(PY_CFLAGS) $(PY_CFLAGS_NODIST) $(PY_CPPFLAGS) $(CFLAGSFORSHARED) -DPy_BUILD_CORE +# Strict or non-strict aliasing flags used to compile dtoa.c, see above +CFLAGS_ALIASING=@CFLAGS_ALIASING@ # Machine-dependent subdirectories @@ -1536,6 +1538,13 @@ config.status: $(srcdir)/configure .c.o: $(CC) -c $(PY_CORE_CFLAGS) -o $@ $< +# bpo-30104: dtoa.c uses union to cast double to unsigned long[2]. clang 4.0 +# with -O2 or higher and strict aliasing miscompiles the ratio() function +# causing rounding issues. Compile dtoa.c using -fno-strict-aliasing on clang. +# https://bugs.llvm.org//show_bug.cgi?id=31928 +Python/dtoa.o: Python/dtoa.c + $(CC) -c $(PY_CORE_CFLAGS) $(CFLAGS_ALIASING) -o $@ $< + # Run reindent on the library reindent: ./$(BUILDPYTHON) $(srcdir)/Tools/scripts/reindent.py -r $(srcdir)/Lib @@ -668,6 +668,7 @@ OTHER_LIBTOOL_OPT UNIVERSAL_ARCH_FLAGS CFLAGS_NODIST BASECFLAGS +CFLAGS_ALIASING OPT LLVM_PROF_FOUND target_os @@ -6829,13 +6830,7 @@ then then # Clang also needs -fwrapv WRAP="-fwrapv" - - # bpo-30104: Python/dtoa.c requires to be build with - # -fno-strict-aliasing to fix compiler issue on the - # double/ULong[2] union using clang 4.0 and optimization level - # -O2 or higher - # https://bugs.llvm.org//show_bug.cgi?id=31928 - ALIASING="-fno-strict-aliasing" + CFLAGS_ALIASING="-fno-strict-aliasing" fi case $ac_cv_prog_cc_g in @@ -6857,7 +6852,7 @@ then ;; esac - OPT="$OPT $STRICT_PROTO $ALIASING" + OPT="$OPT $STRICT_PROTO" case $ac_sys_system in SCO_SV*) OPT="$OPT -m486 -DSCO5" diff --git a/configure.ac b/configure.ac index e5b725795a..c58322dc8c 100644 --- a/configure.ac +++ b/configure.ac @@ -1440,6 +1440,7 @@ esac # tweak OPT based on compiler and platform, only if the user didn't set # it on the command line AC_SUBST(OPT) +AC_SUBST(CFLAGS_ALIASING) if test "${OPT-unset}" = "unset" then case $GCC in @@ -1469,13 +1470,9 @@ then then # Clang also needs -fwrapv WRAP="-fwrapv" - - # bpo-30104: Python/dtoa.c requires to be build with - # -fno-strict-aliasing to fix compiler issue on the - # double/ULong[2] union using clang 4.0 and optimization level - # -O2 or higher - # https://bugs.llvm.org//show_bug.cgi?id=31928 - ALIASING="-fno-strict-aliasing" + # bpo-30104: disable strict aliasing to compile correctly dtoa.c, + # see Makefile.pre.in for more information + CFLAGS_ALIASING="-fno-strict-aliasing" fi case $ac_cv_prog_cc_g in @@ -1497,7 +1494,7 @@ then ;; esac - OPT="$OPT $STRICT_PROTO $ALIASING" + OPT="$OPT $STRICT_PROTO" case $ac_sys_system in SCO_SV*) OPT="$OPT -m486 -DSCO5" |