On Wed, Aug 28, 2024 at 12:24:12PM +0000, Arnd Bergmann wrote: > On Wed, Aug 28, 2024, at 11:18, Jason A. Donenfeld wrote: > > On Tue, Aug 27, 2024 at 05:53:30PM -0500, Segher Boessenkool wrote: > >> On Tue, Aug 27, 2024 at 11:08:19AM -0700, Eric Biggers wrote: > >> > > >> > Is there a compiler flag that could be used to disable the generation of calls > >> > to memset? > >> > >> -fno-tree-loop-distribute-patterns . But, as always, read up on it, see > >> what it actually does (and how it avoids your problem, and mostly: learn > >> what the actual problem *was*!) > > > > This might help with various loops, but it doesn't help with the matter > > that this patch fixes, which is struct initialization. I just tried it > > with the arm64 patch to no avail. > > Maybe -ffreestanding can help here? That should cause the vdso to be built > with the assumption that there is no libc, so it would neither add nor > remove standard library calls. Not sure if that causes other problems, > e.g. if the calling conventions are different. "GCC requires the freestanding environment provide 'memcpy', 'memmove', 'memset' and 'memcmp'." This is precisely to implement things like struct initialisation. Maybe we should have a "-ffreeerstanding" or "-ffreefloating" or think of something funnier still environment as well, this problem has been there since the -ffreestanding flag has existed, but the problem is as old as the night. -fno-builtin might help a bit more, but just attack the problem at its root, like I suggested? (This isn't a new problem, originally it showed up as "GCC replaces (part of) my memcpy() implementation by a (recursive) call to memcpy()" and, well, that doesn't quite work!) Segher
