Add temporary hack to -Wuninitialize to create a separate CFG (for C++ code)...

Add temporary hack to -Wuninitialize to create a separate CFG (for C++ code) that doesn't include implicit dtors.

Implicit dtors confuse the ad hoc path-sensitivity of UninitializedValuesV2.cpp.  This isn't
the ideal solution, as it will directly impact compile time, but should significantly reduce
the noise of -Wuninitialized on some code bases.

This immediately "fixes" the false positive reported in PR 9063, although this
isn't the right fix in the long run.

llvm-svn: 124667

clang/lib/Sema/AnalysisBasedWarnings.cpp

@@ -519,7 +519,24 @@ AnalysisBasedWarnings::IssueWarnings(sema::AnalysisBasedWarnings::Policy P,
   
   if (Diags.getDiagnosticLevel(diag::warn_uninit_var, D->getLocStart())
       != Diagnostic::Ignored) {
-    if (CFG *cfg = AC.getCFG()) {
+    ASTContext &ctx = D->getASTContext();
+    llvm::OwningPtr<CFG> tmpCFG;
+    bool useAlternateCFG = false;
+    if (ctx.getLangOptions().CPlusPlus) {
+      // Temporary workaround: implicit dtors in the CFG can confuse
+      // the path-sensitivity in the uninitialized values analysis.
+      // For now create (if necessary) a separate CFG without implicit dtors.
+      // FIXME: We should not need to do this, as it results in multiple
+      // CFGs getting constructed.
+      CFG::BuildOptions B;
+      B.AddEHEdges = false;
+      B.AddImplicitDtors = false;
+      B.AddInitializers = true;
+      tmpCFG.reset(CFG::buildCFG(D, AC.getBody(), &ctx, B));
+      useAlternateCFG = true;
+    }
+    CFG *cfg = useAlternateCFG ? tmpCFG.get() : AC.getCFG();
+    if (cfg) {
       UninitValsDiagReporter reporter(S);
       runUninitializedVariablesAnalysis(*cast<DeclContext>(D), *cfg, AC,
                                         reporter);