en Copyright 2015 Java http://172.16.0.5:8080/history/llvm-project-15.0.7/clang/test/SemaCXX/P30636.cpp#9ed4a94d [clang] Expose unreachable fallthrough annotation warningThe Linux kernel has a macro called IS_ENABLED(), which evaluates to aconstant 1 or 0 based on Kconfig selections, allowing C code to beunconditionally enabled or disabled at build time. For example:int foo(struct *a, int b) { switch (b) { case 1: if (a->flag || !IS_ENABLED(CONFIG_64BIT)) return 1; __attribute__((fallthrough)); case 2: return 2; default: return 3; }}There is an unreachable warning about the fallthrough annotation in thefirst case because !IS_ENABLED(CONFIG_64BIT) can be evaluated to 1,which looks like return 1; __attribute__((fallthrough));to clang.This type of warning is pointless for the Linux kernel because it doesthis trick all over the place due to the sheer number of configurationoptions that it has.Add -Wunreachable-code-fallthrough, enabled under -Wunreachable-code, sothat projects that want to warn on unreachable code get this warning butprojects that do not care about unreachable code can still use-Wimplicit-fallthrough without having to make changes to their codebase.Fixes PR51094.Reviewed By: aaron.ballman, nickdesaulniersDifferential Revision: https://reviews.llvm.org/D107933 List of files: /llvm-project-15.0.7/clang/test/SemaCXX/P30636.cpp Tue, 17 Aug 2021 00:11:07 +0000 Nathan Chancellor <nathan@kernel.org> http://172.16.0.5:8080/history/llvm-project-15.0.7/clang/test/SemaCXX/P30636.cpp#7532d379 Suppress warning on unreachable [[clang::fallthrough]] within a template instantiation.We don't know whether some other instantiation of the template might be able toreach the annotation, so warning on it has a high chance of false positives.Patch by Ahmed Asadi!Differential Revision: https://reviews.llvm.org/D31069llvm-svn: 298477 List of files: /llvm-project-15.0.7/clang/test/SemaCXX/P30636.cpp Wed, 22 Mar 2017 01:49:19 +0000 Richard Smith <richard-llvm@metafoo.co.uk>