On Tue, Aug 24, 2021 at 11:58:59AM +1000, Stephen Rothwell wrote: > On Mon, 23 Aug 2021 18:24:44 -0700 Randy Dunlap <rdunlap@xxxxxxxxxxxxx> wrote: > > > > This is just weird. What I am seeing is that for every source file > > where gcc emits a warning: it then follows that up with this > > >> cc1: warning: unrecognized command line option '-Wno-alloc-size-larger-than' > > I see the same, as well as: > > <stdin>:1515:2: warning: #warning syscall clone3 not implemented [-Wcpp] > cc1: warning: unrecognized command line option '-Wno-alloc-size-larger-than' > > But only on my gcc 7.3.1 builds (the rest are gcc 10). > > > Smells like a gcc bug to me. > > Yes > > Also noted here: https://github.com/DynamoRIO/drmemory/issues/2099 (second comment) Okay, I think this work-around should work. I've been able to reproduce the weird conditions, and this seems to behave correctly. Andrew, can you fixup the fixup with this? diff --git a/Makefile b/Makefile index 26640899e7ca..c1842014a5de 100644 --- a/Makefile +++ b/Makefile @@ -1094,8 +1094,13 @@ endif ifdef CONFIG_CC_IS_GCC # The allocators already balk at large sizes, so silence the compiler -# warnings for bounds checks involving those possible values. -KBUILD_CFLAGS += $(call cc-option, -Wno-alloc-size-larger-than) +# warnings for bounds checks involving those possible values. While +# -Wno-alloc-size-larger-than would normally be used here, some versions +# of gcc (<9.1) weirdly don't handle the option correctly when _other_ +# warnings are produced (?!), so instead use SIZE_MAX to effectively +# disable it. +# https://lore.kernel.org/lkml/20210824115859.187f272f@xxxxxxxxxxxxxxxx +KBUILD_CFLAGS += $(call cc-option, -Walloc-size-larger-than=SIZE_MAX) endif # disable invalid "can't wrap" optimizations for signed / pointers -- Kees Cook
