From: Ted Kremenek <kremenek@apple.com>
Date: Mon, 12 Nov 2012 21:20:48 +0000 (+0000)
Subject: Per discussion on cfe-dev, re-enable suppression of -Wimplicit-fallthrough on C,... 
X-Git-Url: https://granicus.if.org/sourcecode?a=commitdiff_plain;h=3078353fb56772193b9304510048ac075a2c95b5;p=clang

Per discussion on cfe-dev, re-enable suppression of -Wimplicit-fallthrough on C, but also include dialects of C++ earlier than C++11.

There was enough consensus that we *can* get a good language solution
to have an annotation outside of C++11, and without this annotation
this warning doesn't quite mean's completeness criteria for this
kind of warning.  For now, restrict this warning to C++11 (where an
annotation exists), and make this the behavior for the LLVM 3.2 release.
Afterwards, we will hammer out a language solution that we are all
happy with.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@167749 91177308-0d34-0410-b5e6-96231b3b80d8
---

diff --git a/lib/Sema/AnalysisBasedWarnings.cpp b/lib/Sema/AnalysisBasedWarnings.cpp
index a20817f965..801a1b1e02 100644
--- a/lib/Sema/AnalysisBasedWarnings.cpp
+++ b/lib/Sema/AnalysisBasedWarnings.cpp
@@ -818,6 +818,18 @@ namespace {
 
 static void DiagnoseSwitchLabelsFallthrough(Sema &S, AnalysisDeclContext &AC,
                                             bool PerFunction) {
+  // Only perform this analysis when using C++11.  There is no good workflow
+  // for this warning when not using C++11.  There is no good way to silence
+  // the warning (no attribute is available) unless we are using C++11's support
+  // for generalized attributes.  Once could use pragmas to silence the warning,
+  // but as a general solution that is gross and not in the spirit of this
+  // warning.
+  //
+  // NOTE: This an intermediate solution.  There are on-going discussions on
+  // how to properly support this warning outside of C++11 with an annotation.
+  if (!AC.getASTContext().getLangOpts().CPlusPlus0x)
+    return;
+
   FallthroughMapper FM(S);
   FM.TraverseStmt(AC.getBody());
 
diff --git a/test/SemaCXX/switch-implicit-fallthrough-cxx98.cpp b/test/SemaCXX/switch-implicit-fallthrough-cxx98.cpp
index 14ffcef704..8b24c4a3b1 100644
--- a/test/SemaCXX/switch-implicit-fallthrough-cxx98.cpp
+++ b/test/SemaCXX/switch-implicit-fallthrough-cxx98.cpp
@@ -1,5 +1,8 @@
 // RUN: %clang_cc1 -fsyntax-only -verify -std=c++98 -Wimplicit-fallthrough %s
+// XFAIL: *
 
+// NOTE: This test is marked XFAIL until we come up with a good language design
+// for a worfklow to use this warning outside of C++11.
 
 int fallthrough(int n) {
   switch (n / 10) {