On Mon, Aug 24, 2020 at 10:34 AM Arvind Sankar <nived...@alum.mit.edu> wrote: > > On Tue, Aug 25, 2020 at 12:57:22AM +0900, Masahiro Yamada wrote: > > > > > > To prevent transformation from foo() into bar(), > > there are two ways in Clang to do that; > > -fno-builtin-foo, and -fno-builtin-bar. > > There is only one in GCC; -fno-buitin-foo. > > > > Is this correct? > > > > It looked that way from previous experimentation, but... > > > > > > > I just played the optimization > > from printf("helloworld\n") to puts("helloworld"). > > > > https://godbolt.org/z/5s4ded > > > > > > -fno-builtin-puts cannot prevent clang > > from emitting puts. > > Is it because clang does not support > > -fno-builtin-puts? > > Ugh. clang doesn't have __builtin_puts() but it optimizes printf() into > puts(). It doesn't have __builtin_putchar() but will optimize > printf("c") into putchar('c').
Bah, merely a <strikethrough>flesh wound</strikethrough><strikethrough>compiler bug</strikethrough>rather long TODO in the compiler. https://github.com/llvm/llvm-project/blob/be2bc7d4cef2edd66c7fb74b70adf62fc68754db/clang/include/clang/Basic/Builtins.def#L943 Anyways, give me a week and I'll hack through the rest of them https://reviews.llvm.org/D86508. Certainly made HPA's point hit home, that's a lot of functionality to implement or disable in an environment. Masahiro, are you implying that we shouldn't take the -fno-builtin-stpcpy patch, because Clang is inconsistent? (That can be fixed.) Even though -fno-builtin-stpcpy works here as intended? https://lore.kernel.org/lkml/20200817220212.338670-2-ndesaulni...@google.com/ Otherwise we need to provide an implementation of this symbol in the kernel. https://lore.kernel.org/lkml/20200815020946.1538085-1-ndesaulni...@google.com/ Please, pick your poison. -- Thanks, ~Nick Desaulniers