[-Wunreachable-code] include some enum constants in "configuration value" heuristic

llvm-svn: 203026

2 files changed, 23 insertions, 0 deletions

diff --git a/clang/lib/Analysis/ReachableCode.cpp b/clang/lib/Analysis/ReachableCode.cpp
index f159642db2f..b772145456e 100644
--- a/clang/lib/Analysis/ReachableCode.cpp
+++ b/clang/lib/Analysis/ReachableCode.cpp
@@ -376,6 +376,11 @@ static bool isConfigurationValue(const Stmt *S) {
     S = Ex->IgnoreParenCasts();
 
   switch (S->getStmtClass()) {
+    case Stmt::DeclRefExprClass: {
+      const DeclRefExpr *DR = cast<DeclRefExpr>(S);
+      const EnumConstantDecl *ED = dyn_cast<EnumConstantDecl>(DR->getDecl());
+      return ED ? isConfigurationValue(ED->getInitExpr()) : false;
+    }
     case Stmt::IntegerLiteralClass:
       return isExpandedFromConfigurationMacro(S);
     case Stmt::UnaryExprOrTypeTraitExprClass:
diff --git a/clang/test/Sema/warn-unreachable.c b/clang/test/Sema/warn-unreachable.c
index e8089aaa4f9..a3c49855905 100644
--- a/clang/test/Sema/warn-unreachable.c
+++ b/clang/test/Sema/warn-unreachable.c
@@ -234,3 +234,21 @@ int sizeof_int() {
   return 2; // no-warning
 }
 
+enum MyEnum {
+  ME_A = CONFIG_CONSTANT,
+  ME_B = 1
+};
+
+int test_MyEnum() {
+  if (!ME_A)
+    return 1; // no-warning
+  if (ME_A)
+    return 2; // no-warning
+  if (ME_B)
+    return 3;
+  // FIXME: we should only need one diagnostic here.
+  if (!ME_B) // expected-warning {{will never be executed}}
+    return 4;// expected-warning {{will never be executed}}
+  return 5;
+}
+