511972 2025-11-11 22:04:50 +0000 valgrind-3.26.0 tests fail to build on upcomig gcc-16: unrecognized command-line option '-Wno-alloc-size-larger-than=18446744073709551615' 2026-01-07 14:39:33 +0000 1 1 6 Developer tools valgrind general 3.26 GIT Other Linux RESOLVED FIXED NOR normal --- 0 slyich pjfloyd mark pjfloyd sam slyich 0 oldest_to_newest 2469667 0 slyich 2025-11-11 22:04:50 +0000 SUMMARY gcc-16 added extra validation to `-Wno-` options comared to `-W` options in https://gcc.gnu.org/git/?p=gcc.git;a=commitdiff;h=5b276d38c2fdd7df3d167755940da2038e049308 As a result `-Walloc-size-larger-than=18446744073709551615` is not valid flag while `-Wno-alloc-size-larger-than=18446744073709551615` is invalid and the build fails as: gcc -DHAVE_CONFIG_H -I. -I../.. -I../.. -I../../include -I../../coregrind -I../../include -I../../VEX/pub -I../../VEX/pub -DVGA_amd64=1 -DVGO_linux=1 -DVGP_amd64_linux=1 -DVGPV_amd64_linux_vanilla=1 -Winline -Wall -Wshadow -Wno-long-long -g -fno-stack-protector -m64 -Wno-unused-result -Wno-alloc-size-larger-than=18446744073709551615 -MT bug155125-bug155125.o -MD -MP -MF .deps/bug155125-bug155125.Tpo -c -o bug155125-bug155125.o `test -f 'bug155125.c' || echo './'`bug155125.c gcc: error: unrecognized command-line option '-Wno-alloc-size-larger-than=18446744073709551615' STEPS TO REPRODUCE 1. install `gcc` from `master` 2. $ ./configure CC=gcc-16 CXX=g++-16 3. $ make check OBSERVED RESULT Build fails with `gcc: error: unrecognized command-line option '-Wno-alloc-size-larger-than=18446744073709551615'` EXPECTED RESULT Build should succeed. SOFTWARE/OS VERSIONS compiler: gcc from master branch ADDITIONAL INFORMATION The bug happens because `configure.ac` only probes `-Walloc-size-larger-than=18446744073709551615` option and assumes `-Wno-alloc-size-larger-than=18446744073709551615` would work automatically: From configure.ac: ``` AC_DEFUN([AC_GCC_WARNING_SUBST_NO],[ AC_MSG_CHECKING([if gcc accepts -W$1]) safe_CFLAGS=$CFLAGS CFLAGS="-W$1 -Werror" dnl <---------------- probe -W =============== AC_COMPILE_IFELSE([AC_LANG_PROGRAM([[]], [[;]])], [ AC_SUBST([$2], [-Wno-$1]) dnl <---------------- assume -Wno- ========= AC_MSG_RESULT([yes])], [ AC_SUBST([$2], []) AC_MSG_RESULT([no])]) CFLAGS=$safe_CFLAGS ]) ... AC_GCC_WARNING_SUBST_NO([alloc-size-larger-than=18446744073709551615], [FLAG_W_NO_ALLOC_SIZE_LARGER_THAN]) ``` It used to work until https://gcc.gnu.org/git/?p=gcc.git;a=commitdiff;h=5b276d38c2fdd7df3d167755940da2038e049308 A simple workaround to check both forms of the flag restores the build for me: ```diff --- a/configure.ac +++ b/configure.ac @@ -2538,7 +2538,7 @@ fi AC_DEFUN([AC_GCC_WARNING_SUBST_NO],[ AC_MSG_CHECKING([if gcc accepts -W$1]) safe_CFLAGS=$CFLAGS - CFLAGS="-W$1 -Werror" + CFLAGS="-W$1 -Wno-$1 -Werror" AC_COMPILE_IFELSE([AC_LANG_PROGRAM([[]], [[;]])], [ AC_SUBST([$2], [-Wno-$1]) AC_MSG_RESULT([yes])], [ ``` 2469668 1 186714 slyich 2025-11-11 22:09:22 +0000 Created attachment 186714 0001-bug-511972-check-for-both-W-and-Wno-warning-forms-gc.patch 0001-bug-511972-check-for-both-W-and-Wno-warning-forms-gc.patch implements `-W` / `-Wno-` option probing. 2469676 2 sam 2025-11-11 23:41:37 +0000 *** Bug 511974 has been marked as a duplicate of this bug. *** 2469731 3 pjfloyd 2025-11-12 08:25:24 +0000 Does that now mean that GCC generates "alloc size larger than" warnings because it no longer supports '-Wno-alloc-size-larger-than=18446744073709551615 ? 2469753 4 mark 2025-11-12 10:16:42 +0000 This feels like a regression in GCC. Why wouldn't it accept the -Wno variant that is accepted pre-gcc-16? Might it just get fixed in GCC 16 (which is still a couple of months away) if we just report it against GCC? 2469862 5 pjfloyd 2025-11-12 20:50:15 +0000 I've changed the -Wno-alloc-size-larger-than=18446744073709551615 options to -Walloc-size-larger-than=18446744073709551616, which is more than the value that we are using (usually -1 converted to size_t). Seems to work with clang 19 and gcc 14. commit 51c5973d9d1f096b9472df75638f2a53324fafed (HEAD -> master, origin/master, origin/HEAD) Author: Paul Floyd <pjfloyd@wanadoo.fr> Date: Wed Nov 12 21:46:23 2025 +0100 Bug 511972 - valgrind-3.26.0 tests fail to build on upcomig gcc-16: unrecognized command-line option '-Wno-alloc-size-larger-than=18446744073709551615' Initial patch from Sergei Trofimovich, thanks. 2469881 6 slyich 2025-11-12 22:08:08 +0000 (In reply to Mark Wielaard from comment #4) > This feels like a regression in GCC. Why wouldn't it accept the -Wno variant > that is accepted pre-gcc-16? > Might it just get fixed in GCC 16 (which is still a couple of months away) > if we just report it against GCC? I think the change is intentional, but not sure. Added a comment to https://gcc.gnu.org/PR122243#c16. 2469887 7 slyich 2025-11-12 22:25:05 +0000 (In reply to Paul Floyd from comment #3) > Does that now mean that GCC generates "alloc size larger than" warnings > because it no longer supports > '-Wno-alloc-size-larger-than=18446744073709551615 ? Yeah, the original change resurfaced the warnings again. Your change still keeps it suppressed \o/ (In reply to Paul Floyd from comment #5) > I've changed the -Wno-alloc-size-larger-than=18446744073709551615 options to > -Walloc-size-larger-than=18446744073709551616, which is more than the value > that we are using (usually -1 converted to size_t). Seems to work with clang > 19 and gcc 14. > > commit 51c5973d9d1f096b9472df75638f2a53324fafed (HEAD -> master, > origin/master, origin/HEAD) Works for `gcc-16` as well. No alloc-size related warnings. Thank you! The only new warning in `gcc-16` (unrelated to `-Wno-`) is: new_override.cpp:21:16: warning: variable 'j' set but not used [-Wunused-but-set-variable=] 21 | volatile int j = 0; | ^ An effect of https://gcc.gnu.org/PR44677 ( https://gcc.gnu.org/r16-2258-g0eac9cfee8cb0b21d ). 2482628 8 mark 2026-01-07 14:39:33 +0000 Also backported to the VALGRIND_3_26_BRANCH as commit fc9cf49c2f2e0e2282b000557df80ce2f755f191 (HEAD -> VALGRIND_3_26_BRANCH) Author: Paul Floyd <pjfloyd@wanadoo.fr> Date: Wed Nov 12 21:46:23 2025 +0100 Bug 511972 - valgrind-3.26.0 tests fail to build on upcomig gcc-16: unrecognized command-line option '-Wno-alloc-size-larger-than=18446744073709551615' Initial patch from Sergei Trofimovich, thanks. (cherry picked from commit 51c5973d9d1f096b9472df75638f2a53324fafed) 186714 2025-11-11 22:09:22 +0000 2025-11-11 22:09:22 +0000 0001-bug-511972-check-for-both-W-and-Wno-warning-forms-gc.patch 0001-bug-511972-check-for-both-W-and-Wno-warning-forms-gc.patch text/plain 1233 slyich RnJvbSA0N2I0MGQ4NzgzNDVhZGI1YzNjNTA5YmQxYjkwYjJhNGUwOGIyYWM1IE1vbiBTZXAgMTcg MDA6MDA6MDAgMjAwMQpGcm9tOiBTZXJnZWkgVHJvZmltb3ZpY2ggPHNseWljaEBnbWFpbC5jb20+ CkRhdGU6IFR1ZSwgMTEgTm92IDIwMjUgMjI6MDU6MDcgKzAwMDAKU3ViamVjdDogW1BBVENIXSBi dWcgNTExOTcyIC0gY2hlY2sgZm9yIGJvdGggLVcgYW5kIC1Xbm8tIHdhcm5pbmcgZm9ybXMKIChn Y2MtMTYpCgpXaXRob3V0IHRoZSBjaGFuZ2UgYG1ha2UgY2hlY2tgIG9uIHVwY29taW5nIGBnY2Mt MTZgIGZhaWxzIGFzOgoKICAgICQgbWFrZSBjaGVjawogICAgZ2NjOiBlcnJvcjogdW5yZWNvZ25p emVkIGNvbW1hbmQtbGluZSBvcHRpb24gJy1Xbm8tYWxsb2Mtc2l6ZS1sYXJnZXItdGhhbj0xODQ0 Njc0NDA3MzcwOTU1MTYxNScKClRoaXMgaGFwcGVucyBiZWNhdXNlIGBnY2NgIHJlY2VudGx5IGlu Y3JlYXNlZCBzdHJpY3RuZXNzIG9mIGAtV25vLWAgZmxhZ3MKY2hlY2tzIGluIGh0dHBzOi8vZ2Nj LmdudS5vcmcvZ2l0Lz9wPWdjYy5naXQ7YT1jb21taXRkaWZmO2g9NWIyNzZkMzhjMmZkZDdkZjNk MTY3NzU1OTQwZGEyMDM4ZTA0OTMwOAphbmQgc3RhcnRlZCByZWplY3RpbmcgYXJndW1lbnQgZm9y IG9mIHRob3NlLgoKVGhlIGNoYW5nZSB2YWxpZGF0ZXMgYm90aCBgLVdgIGFuZCBgLVduby1gIGZv cm1zIHRvIGF2b2lkIHBhc3NpbmcKdW50ZXN0ZWQgZmxhZ3MgdG8gdGhlIGNvbXBpbGVyLgotLS0K IGNvbmZpZ3VyZS5hYyB8IDIgKy0KIDEgZmlsZSBjaGFuZ2VkLCAxIGluc2VydGlvbigrKSwgMSBk ZWxldGlvbigtKQoKZGlmZiAtLWdpdCBhL2NvbmZpZ3VyZS5hYyBiL2NvbmZpZ3VyZS5hYwppbmRl eCAwMDkyYWQyYWUuLjE3MWZlOTlmNSAxMDA2NDQKLS0tIGEvY29uZmlndXJlLmFjCisrKyBiL2Nv bmZpZ3VyZS5hYwpAQCAtMjUzOCw3ICsyNTM4LDcgQEAgZmkKIEFDX0RFRlVOKFtBQ19HQ0NfV0FS TklOR19TVUJTVF9OT10sWwogICBBQ19NU0dfQ0hFQ0tJTkcoW2lmIGdjYyBhY2NlcHRzIC1XJDFd KQogICBzYWZlX0NGTEFHUz0kQ0ZMQUdTCi0gIENGTEFHUz0iLVckMSAtV2Vycm9yIgorICBDRkxB R1M9Ii1XJDEgLVduby0kMSAtV2Vycm9yIgogICBBQ19DT01QSUxFX0lGRUxTRShbQUNfTEFOR19Q Uk9HUkFNKFtbXV0sIFtbO11dKV0sIFsKICAgQUNfU1VCU1QoWyQyXSwgWy1Xbm8tJDFdKQogICBB Q19NU0dfUkVTVUxUKFt5ZXNdKV0sIFsKLS0gCjIuNTEuMAoK