[CFG] Fix an assertion failure with static initializers

The CFGBlock::getLastCondition was not prepared for static initializer
branches.

This patch also revamps CFG unit tests. Earlier the lifetime of the AST
was smaller than the CFG. So all the AST pointers within the CFG blocks
were dangling. This was OK, since none of the tests dereferenced those
pointers. This was, however, a timed bomb. There were patches in the
past that were reverted partially due to this problem.

Differential revision: https://reviews.llvm.org/D71791

clang/lib/Analysis/CFG.cpp

@@ -5919,7 +5919,7 @@ const Expr *CFGBlock::getLastCondition() const {
     return nullptr;
 
   const Stmt *Cond = StmtElem->getStmt();
-  if (isa<ObjCForCollectionStmt>(Cond))
+  if (isa<ObjCForCollectionStmt>(Cond) || isa<DeclStmt>(Cond))
     return nullptr;
 
   // Only ObjCForCollectionStmt is known not to be a non-Expr terminator, hence

clang/unittests/Analysis/CFGBuildResult.h

@@ -6,9 +6,10 @@
 //
 //===----------------------------------------------------------------------===//
 
-#include "clang/Analysis/CFG.h"
 #include "clang/ASTMatchers/ASTMatchFinder.h"
+#include "clang/Analysis/CFG.h"
 #include "clang/Tooling/Tooling.h"
+#include <memory>
 
 namespace clang {
 namespace analysis {
@@ -22,20 +23,27 @@ public:
     BuiltCFG,
   };
 
-  BuildResult(Status S, std::unique_ptr<CFG> Cfg = nullptr)
-      : S(S), Cfg(std::move(Cfg)) {}
+  BuildResult(Status S, std::unique_ptr<CFG> Cfg = nullptr,
+              std::unique_ptr<ASTUnit> AST = nullptr)
+      : S(S), Cfg(std::move(Cfg)), AST(std::move(AST)) {}
 
   Status getStatus() const { return S; }
   CFG *getCFG() const { return Cfg.get(); }
+  ASTUnit *getAST() const { return AST.get(); }
 
 private:
   Status S;
   std::unique_ptr<CFG> Cfg;
+  std::unique_ptr<ASTUnit> AST;
 };
 
 class CFGCallback : public ast_matchers::MatchFinder::MatchCallback {
 public:
+  CFGCallback(std::unique_ptr<ASTUnit> AST) : AST(std::move(AST)) {}
+
+  std::unique_ptr<ASTUnit> AST;
   BuildResult TheBuildResult = BuildResult::ToolRan;
+  CFG::BuildOptions Options;
 
   void run(const ast_matchers::MatchFinder::MatchResult &Result) override {
     const auto *Func = Result.Nodes.getNodeAs<FunctionDecl>("func");
@@ -43,25 +51,26 @@ public:
     if (!Body)
       return;
     TheBuildResult = BuildResult::SawFunctionBody;
-    CFG::BuildOptions Options;
     Options.AddImplicitDtors = true;
     if (std::unique_ptr<CFG> Cfg =
             CFG::buildCFG(nullptr, Body, Result.Context, Options))
-      TheBuildResult = {BuildResult::BuiltCFG, std::move(Cfg)};
+      TheBuildResult = {BuildResult::BuiltCFG, std::move(Cfg), std::move(AST)};
   }
 };
 
-inline BuildResult BuildCFG(const char *Code) {
-  CFGCallback Callback;
-
-  ast_matchers::MatchFinder Finder;
-  Finder.addMatcher(ast_matchers::functionDecl().bind("func"), &Callback);
-  std::unique_ptr<tooling::FrontendActionFactory> Factory(
-      tooling::newFrontendActionFactory(&Finder));
+inline BuildResult BuildCFG(const char *Code, CFG::BuildOptions Options = {}) {
   std::vector<std::string> Args = {"-std=c++11",
                                    "-fno-delayed-template-parsing"};
-  if (!tooling::runToolOnCodeWithArgs(Factory->create(), Code, Args))
+  std::unique_ptr<ASTUnit> AST = tooling::buildASTFromCodeWithArgs(Code, Args);
+  if (!AST)
     return BuildResult::ToolFailed;
+
+  CFGCallback Callback(std::move(AST));
+  Callback.Options = Options;
+  ast_matchers::MatchFinder Finder;
+  Finder.addMatcher(ast_matchers::functionDecl().bind("func"), &Callback);
+
+  Finder.matchAST(Callback.AST->getASTContext());
   return std::move(Callback.TheBuildResult);
 }
 

clang/unittests/Analysis/CFGTest.cpp

@@ -30,6 +30,22 @@ TEST(CFG, RangeBasedForOverDependentType) {
   EXPECT_EQ(BuildResult::SawFunctionBody, BuildCFG(Code).getStatus());
 }
 
+TEST(CFG, StaticInitializerLastCondition) {
+  const char *Code = "void f() {\n"
+                     "  int i = 5 ;\n"
+                     "  static int j = 3 ;\n"
+                     "}\n";
+  CFG::BuildOptions Options;
+  Options.AddStaticInitBranches = true;
+  Options.setAllAlwaysAdd();
+  BuildResult B = BuildCFG(Code, Options);
+  EXPECT_EQ(BuildResult::BuiltCFG, B.getStatus());
+  EXPECT_EQ(1u, B.getCFG()->getEntry().succ_size());
+  CFGBlock *Block = *B.getCFG()->getEntry().succ_begin();
+  EXPECT_TRUE(isa<DeclStmt>(Block->getTerminatorStmt()));
+  EXPECT_EQ(nullptr, Block->getLastCondition());
+}
+
 // Constructing a CFG containing a delete expression on a dependent type should
 // not crash.
 TEST(CFG, DeleteExpressionOnDependentType) {