Further tweak -Wurneachable-code and templates by allowing the warning to run on

explicit template specializations (which represent actual functions somebody wrote).

Along the way, refactor some other code which similarly cares about whether or
not they are looking at a template instantiation.

llvm-svn: 145547

3 files changed, 32 insertions, 17 deletions

diff --git a/clang/lib/AST/Decl.cpp b/clang/lib/AST/Decl.cpp
index 299ddd4b721..7be4d26f985 100644
--- a/clang/lib/AST/Decl.cpp
+++ b/clang/lib/AST/Decl.cpp
@@ -1951,7 +1951,20 @@ bool FunctionDecl::isImplicitlyInstantiable() const {
     return true;
 
   return PatternDecl->isInlined();
-}                      
+}
+
+bool FunctionDecl::isTemplateInstantiation() const {
+  switch (getTemplateSpecializationKind()) {
+    case TSK_Undeclared:
+    case TSK_ExplicitSpecialization:
+      return false;      
+    case TSK_ImplicitInstantiation:
+    case TSK_ExplicitInstantiationDeclaration:
+    case TSK_ExplicitInstantiationDefinition:
+      return true;
+  }
+  llvm_unreachable("All TSK values handled.");
+}
    
 FunctionDecl *FunctionDecl::getTemplateInstantiationPattern() const {
   // Handle class scope explicit specialization special case.
diff --git a/clang/lib/Sema/AnalysisBasedWarnings.cpp b/clang/lib/Sema/AnalysisBasedWarnings.cpp
index 54a26b3253a..fc635fba2dd 100644
--- a/clang/lib/Sema/AnalysisBasedWarnings.cpp
+++ b/clang/lib/Sema/AnalysisBasedWarnings.cpp
@@ -241,19 +241,8 @@ struct CheckFallThroughDiagnostics {
     
     // Don't suggest that template instantiations be marked "noreturn"
     bool isTemplateInstantiation = false;
-    if (const FunctionDecl *Function = dyn_cast<FunctionDecl>(Func)) {
-      switch (Function->getTemplateSpecializationKind()) {
-      case TSK_Undeclared:
-      case TSK_ExplicitSpecialization:
-        break;
-        
-      case TSK_ImplicitInstantiation:
-      case TSK_ExplicitInstantiationDeclaration:
-      case TSK_ExplicitInstantiationDefinition:
-        isTemplateInstantiation = true;
-        break;
-      }
-    }
+    if (const FunctionDecl *Function = dyn_cast<FunctionDecl>(Func))
+      isTemplateInstantiation = Function->isTemplateInstantiation();
         
     if (!isVirtualMethod && !isTemplateInstantiation)
       D.diag_NeverFallThroughOrReturn =
@@ -919,7 +908,10 @@ AnalysisBasedWarnings::IssueWarnings(sema::AnalysisBasedWarnings::Policy P,
     // Different template instantiations can effectively change the control-flow
     // and it is very difficult to prove that a snippet of code in a template
     // is unreachable for all instantiations.
-    if (S.ActiveTemplateInstantiations.empty())
+    bool isTemplateInstantiation = false;
+    if (const FunctionDecl *Function = dyn_cast<FunctionDecl>(D))
+      isTemplateInstantiation = Function->isTemplateInstantiation();
+    if (!isTemplateInstantiation)
       CheckUnreachable(S, AC);
   }
 
diff --git a/clang/lib/StaticAnalyzer/Checkers/UnreachableCodeChecker.cpp b/clang/lib/StaticAnalyzer/Checkers/UnreachableCodeChecker.cpp
index 97cc44f0cbd..2b550df2b93 100644
--- a/clang/lib/StaticAnalyzer/Checkers/UnreachableCodeChecker.cpp
+++ b/clang/lib/StaticAnalyzer/Checkers/UnreachableCodeChecker.cpp
@@ -54,10 +54,11 @@ void UnreachableCodeChecker::checkEndAnalysis(ExplodedGraph &G,
                                               BugReporter &B,
                                               ExprEngine &Eng) const {
   CFGBlocksSet reachable, visited;
-
+  
   if (Eng.hasWorkRemaining())
     return;
 
+  const Decl *D = 0;
   CFG *C = 0;
   ParentMap *PM = 0;
   const LocationContext *LC = 0;
@@ -67,6 +68,8 @@ void UnreachableCodeChecker::checkEndAnalysis(ExplodedGraph &G,
     const ProgramPoint &P = I->getLocation();
     LC = P.getLocationContext();
 
+    if (!D)
+      D = LC->getAnalysisDeclContext()->getDecl();
     // Save the CFG if we don't have it already
     if (!C)
       C = LC->getAnalysisDeclContext()->getUnoptimizedCFG();
@@ -80,8 +83,15 @@ void UnreachableCodeChecker::checkEndAnalysis(ExplodedGraph &G,
   }
 
   // Bail out if we didn't get the CFG or the ParentMap.
-  if (!C || !PM)
+  if (!D || !C || !PM)
     return;
+  
+  // Don't do anything for template instantiations.  Proving that code
+  // in a template instantiation is unreachable means proving that it is
+  // unreachable in all instantiations.
+  if (const FunctionDecl *FD = dyn_cast<FunctionDecl>(D))
+    if (FD->isTemplateInstantiation())
+      return;
 
   // Find CFGBlocks that were not covered by any node
   for (CFG::const_iterator I = C->begin(), E = C->end(); I != E; ++I) {