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GCC union bugs to be fixed in GCC 15.2

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Thanks to Martin Jambor for the GCC fixes; see:
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=117423#c27
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=119085#c12
Also, thanks to Sam James for letting me know.
* configure.ac (emacs_cv_gcc_union_bugs_CFLAGS):
Rename from emacs_cv_gcc_bug_119085_CFLAGS.  All uses changed.
Assume the GCC union bugs will be fixed in GCC 15.2.
This commit is contained in:
Paul Eggert 2025-07-30 18:40:20 -07:00
parent 45a5fae991
commit 0eaf5c045f
1 changed files with 17 additions and 20 deletions
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37
configure.ac
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@ -2214,32 +2214,27 @@ esac
C_SWITCH_MACHINE=
AC_CACHE_CHECK([for flag to work around GCC bug 119085],
[emacs_cv_gcc_bug_119085_CFLAGS],
[emacs_cv_gcc_bug_119085_CFLAGS='none needed'
AC_CACHE_CHECK([for flag to work around GCC union bugs],
[emacs_cv_gcc_union_bugs_CFLAGS],
[emacs_cv_gcc_union_bugs_CFLAGS='none needed'
AS_IF([test "$GCC" = yes],
[old_CFLAGS=$CFLAGS
# Use -fno-tree-sra if GCC 4 through 15.
for emacs_cv_gcc_bug_119085_CFLAGS in \
# Use -fno-tree-sra if GCC 4 through 15.1.
for emacs_cv_gcc_union_bugs_CFLAGS in \
'none needed' -fno-tree-sra
do
AS_CASE([$emacs_cv_gcc_bug_119085_CFLAGS],
AS_CASE([$emacs_cv_gcc_union_bugs_CFLAGS],
['none needed'], [],
[-fno-tree-sra], [break],
[CFLAGS="$old_CFLAGS $emacs_cv_gcc_bug_119085_CFLAGS"])
[CFLAGS="$old_CFLAGS $emacs_cv_gcc_union_bugs_CFLAGS"])
AC_COMPILE_IFELSE(
[AC_LANG_DEFINES_PROVIDED
[/* Work around GCC bug 119085 with unions containing holes:
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=119085
Although GCC bug 119085 is present in GCC 15.1,
as of 2025-07-23 a patch is in the works for GCC 16;
for now, assume the bug exists in GCC versions 4 through 15.
Working around GCC bug 119095 also works around GCC bug 117423
[/* Work around GCC bugs 117423 and 119085 re holes in unions:
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=117423
which as of 2025-07-23 is planned to be fixed in GCC 15.2.
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=119085
These are fixed in GCC 15.2.
Working wround GCC bug 119085 also works around GCC bug 58416
Working wround them also works around GCC bug 58416
with double in unions on x86, where the generated insns
copy non-floating-point data via fldl/fstpl instruction pairs.
This can misbehave if the data's bit pattern looks like a NaN.
@ -2249,16 +2244,18 @@ AC_CACHE_CHECK([for flag to work around GCC bug 119085],
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=93271
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=114659
GCC bug 58416 is fixed in GCC 15.1. */
#if 4 <= __GNUC__ && __GNUC__ <= 15 && !defined __clang__
# error "GCC bug 119085 possibly present"
#if 4 <= __GNUC__ && ! (15 < __GNUC__ + (1 < __GNUC_MINOR__))
#ifndef __clang__
#error "GCC union bugs possibly present"
#endif
#endif
]],
[break])
done
CFLAGS=$old_CFLAGS])])
AS_CASE([$emacs_cv_gcc_bug_119085_CFLAGS],
AS_CASE([$emacs_cv_gcc_union_bugs_CFLAGS],
[-*],
[C_SWITCH_MACHINE="$C_SWITCH_MACHINE $emacs_cv_gcc_bug_119085_CFLAGS"])
[C_SWITCH_MACHINE="$C_SWITCH_MACHINE $emacs_cv_gcc_union_bugs_CFLAGS"])
AC_SUBST([C_SWITCH_MACHINE])