[llvm] r280326 - Support: Avoid errors with LLVM_FALLTHROUGH in clang 3.6 and below in C mode

[Justin Bogner via llvm-commits]

Author: bogner
Date: Wed Aug 31 18:43:14 2016
New Revision: 280326

URL: http://llvm.org/viewvc/llvm-project?rev=280326&view=rev
Log:
Support: Avoid errors with LLVM_FALLTHROUGH in clang 3.6 and below in C mode

Older versions of clang defined __has_cpp_attribute in C mode, but
would choke on scoped attributes, as per llvm.org/PR23435. Since we
support building with clang all the way back to 3.1, we have to work
around this issue.

Modified:
    llvm/trunk/include/llvm/Support/Compiler.h

Modified: llvm/trunk/include/llvm/Support/Compiler.h
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/include/llvm/Support/Compiler.h?rev=280326&r1=280325&r2=280326&view=diff
==============================================================================
--- llvm/trunk/include/llvm/Support/Compiler.h (original)
+++ llvm/trunk/include/llvm/Support/Compiler.h Wed Aug 31 18:43:14 2016
@@ -235,6 +235,10 @@
 /// LLVM_FALLTHROUGH - Mark fallthrough cases in switch statements.
 #if __cplusplus > 201402L && __has_cpp_attribute(fallthrough)
 #define LLVM_FALLTHROUGH [[fallthrough]]
+#elif !__cplusplus
+// Workaround for llvm.org/PR23435, since clang 3.6 and below emit a spurious
+// error when __has_cpp_attribute is given a scoped attribute in C mode.
+#define LLVM_FALLTHROUGH
 #elif __has_cpp_attribute(clang::fallthrough)
 #define LLVM_FALLTHROUGH [[clang::fallthrough]]
 #else