On Tue, Jun 25, 2019 at 5:47 AM Miguel Ojeda <miguel.ojeda.sando...@gmail.com> wrote: > > On Tue, Jun 25, 2019 at 9:19 AM Peter Zijlstra <pet...@infradead.org> wrote: > > > > Can it build a kernel without patches yet? That is, why should I care > > what LLVM does?
Unreleased versions of Clang built from source can; the latest release of Clang-8 doesn't have asm goto support required for CONFIG_JUMP_LABEL. Things can get complicated based on which kernel tree/branch (mainline, -next, stable), arch, and configs, but I think we just have a few long tail bugs left. We're currently planning multiple output constraint support w/ asm goto, and have recently implemented things like __GCC_ASM_FLAG_OUTPUTS__. If there's other features that we should start implementing, please let us know. Give it a shot and let us know what works or doesn't. For more info, see our site: https://clangbuiltlinux.github.io/ CI: https://travis-ci.com/ClangBuiltLinux/continuous-integration Bug tracker: https://github.com/ClangBuiltLinux/linux/issues wiki: https://github.com/ClangBuiltLinux/linux/wiki Or reach out to us via email: clang-built-li...@googlegroups.com irc: #clangbuiltlinux on chat.freenode.net or attend our public bi-weekly (once ever 2 weeks, not twice a week) meeting > > Having more than a single compiler is always a good idea. You benefit > from more warnings, more tooling, a second implementation for > reference/comparison, etc. > > As for what is the current state, I think they are close, specially > for aarch64, but I let Nick, Nathan et. al. answer that! :-) (Cc'd). > They had a talk in FOSDEM 2019 about it, too. > > Also CC'ing Luc since he changed sparse to stop ignoring the attribute > so that __has_attribute() would work, but I am not sure if there has > been further work on supporting it properly. > > > > Also note that C2x may get [[fallthrough]]. See N2267 and N2335. At > > > that point, surely tools/IDEs/analyzers will support it :-) The > > > question is whether we want to wait that long to replace the comments. > > > > #define __fallthrough [[fallthrough]] > > > > right? > > Yes and no. The exact spelling we use does not matter much. My point > with that paragraph was that since C2x will (maybe) add fallthrough, > as C++17 did, every compiler/analyzer/IDE/etc. that is still missing > support for it will have to eventually add it even if they ignore GNU > attributes. At that point, I would guess most will likely add all > spellings too. Regarding __attribute__((fallthrough)), it's currently a work in progress in Clang: https://bugs.llvm.org/show_bug.cgi?id=37135 https://reviews.llvm.org/D63260 -- Thanks, ~Nick Desaulniers
