[Analyzer][CFG] Correctly handle rebuilt default arg and default init expression

Signed-off-by: yronglin <[email protected]>

Author: yronglin

clang/docs/ReleaseNotes.rst

@@ -270,6 +270,10 @@ Code Completion
 Static Analyzer
 ---------------
 
+- Clang currently support extending lifetime of object bound to 
+  reference members of aggregates in CFG and ExprEngine, that are
+  created from default member initializer.
+
 New features
 ^^^^^^^^^^^^
 

clang/lib/AST/ParentMap.cpp

@@ -13,6 +13,7 @@
 #include "clang/AST/ParentMap.h"
 #include "clang/AST/Decl.h"
 #include "clang/AST/Expr.h"
+#include "clang/AST/ExprCXX.h"
 #include "clang/AST/StmtObjC.h"
 #include "llvm/ADT/DenseMap.h"
 
@@ -103,6 +104,22 @@ static void BuildParentMap(MapTy& M, Stmt* S,
       BuildParentMap(M, SubStmt, OVMode);
     }
     break;
+  case Stmt::CXXDefaultArgExprClass:
+    if (auto *Arg = dyn_cast<CXXDefaultArgExpr>(S)) {
+      if (Arg->hasRewrittenInit()) {
+        M[Arg->getExpr()] = S;
+        BuildParentMap(M, Arg->getExpr(), OVMode);
+      }
+    }
+    break;
+  case Stmt::CXXDefaultInitExprClass:
+    if (auto *Init = dyn_cast<CXXDefaultInitExpr>(S)) {
+      if (Init->hasRewrittenInit()) {
+        M[Init->getExpr()] = S;
+        BuildParentMap(M, Init->getExpr(), OVMode);
+      }
+    }
+    break;
   default:
     for (Stmt *SubStmt : S->children()) {
       if (SubStmt) {

clang/lib/Analysis/CFG.cpp

@@ -556,6 +556,10 @@ class CFGBuilder {
 
 private:
   // Visitors to walk an AST and construct the CFG.
+  CFGBlock *VisitCXXDefaultArgExpr(CXXDefaultArgExpr *Default,
+                                   AddStmtChoice asc);
+  CFGBlock *VisitCXXDefaultInitExpr(CXXDefaultInitExpr *Default,
+                                    AddStmtChoice asc);
   CFGBlock *VisitInitListExpr(InitListExpr *ILE, AddStmtChoice asc);
   CFGBlock *VisitAddrLabelExpr(AddrLabelExpr *A, AddStmtChoice asc);
   CFGBlock *VisitAttributedStmt(AttributedStmt *A, AddStmtChoice asc);
@@ -2263,16 +2267,10 @@ CFGBlock *CFGBuilder::Visit(Stmt * S, AddStmtChoice asc,
                                    asc, ExternallyDestructed);
 
     case Stmt::CXXDefaultArgExprClass:
+      return VisitCXXDefaultArgExpr(cast<CXXDefaultArgExpr>(S), asc);
+
     case Stmt::CXXDefaultInitExprClass:
-      // FIXME: The expression inside a CXXDefaultArgExpr is owned by the
-      // called function's declaration, not by the caller. If we simply add
-      // this expression to the CFG, we could end up with the same Expr
-      // appearing multiple times (PR13385).
-      //
-      // It's likewise possible for multiple CXXDefaultInitExprs for the same
-      // expression to be used in the same function (through aggregate
-      // initialization).
-      return VisitStmt(S, asc);
+      return VisitCXXDefaultInitExpr(cast<CXXDefaultInitExpr>(S), asc);
 
     case Stmt::CXXBindTemporaryExprClass:
       return VisitCXXBindTemporaryExpr(cast<CXXBindTemporaryExpr>(S), asc);
@@ -2442,6 +2440,40 @@ CFGBlock *CFGBuilder::VisitChildren(Stmt *S) {
   return B;
 }
 
+CFGBlock *CFGBuilder::VisitCXXDefaultArgExpr(CXXDefaultArgExpr *Arg,
+                                             AddStmtChoice asc) {
+  if (Arg->hasRewrittenInit()) {
+    if (asc.alwaysAdd(*this, Arg)) {
+      autoCreateBlock();
+      appendStmt(Block, Arg);
+    }
+    return VisitStmt(Arg->getExpr(), asc);
+  }
+
+  // We can't add the default argument if it's not rewritten because the
+  // expression inside a CXXDefaultArgExpr is owned by the called function's
+  // declaration, not by the caller, we could end up with the same expression
+  // appearing multiple times.
+  return VisitStmt(Arg, asc);
+}
+
+CFGBlock *CFGBuilder::VisitCXXDefaultInitExpr(CXXDefaultInitExpr *Init,
+                                              AddStmtChoice asc) {
+  if (Init->hasRewrittenInit()) {
+    if (asc.alwaysAdd(*this, Init)) {
+      autoCreateBlock();
+      appendStmt(Block, Init);
+    }
+    return VisitStmt(Init->getExpr(), asc);
+  }
+
+  // We can't add the default initializer if it's not rewritten because multiple
+  // CXXDefaultInitExprs for the same sub-expression to be used in the same
+  // function (through aggregate initialization). we could end up with the same
+  // expression appearing multiple times.
+  return VisitStmt(Init, asc);
+}
+
 CFGBlock *CFGBuilder::VisitInitListExpr(InitListExpr *ILE, AddStmtChoice asc) {
   if (asc.alwaysAdd(*this, ILE)) {
     autoCreateBlock();

clang/lib/Analysis/ReachableCode.cpp

@@ -454,11 +454,12 @@ bool DeadCodeScan::isDeadCodeRoot(const clang::CFGBlock *Block) {
   return isDeadRoot;
 }
 
-// Check if the given `DeadStmt` is a coroutine statement and is a substmt of
-// the coroutine statement. `Block` is the CFGBlock containing the `DeadStmt`.
-static bool isInCoroutineStmt(const Stmt *DeadStmt, const CFGBlock *Block) {
+// Check if the given `DeadStmt` is one of target statements or is a sub-stmt of
+// them. `Block` is the CFGBlock containing the `DeadStmt`.
+template <class... Ts>
+static bool isDeadStmtInOneOf(const Stmt *DeadStmt, const CFGBlock *Block) {
   // The coroutine statement, co_return, co_await, or co_yield.
-  const Stmt *CoroStmt = nullptr;
+  const Stmt *TargetStmt = nullptr;
   // Find the first coroutine statement after the DeadStmt in the block.
   bool AfterDeadStmt = false;
   for (CFGBlock::const_iterator I = Block->begin(), E = Block->end(); I != E;
@@ -467,32 +468,27 @@ static bool isInCoroutineStmt(const Stmt *DeadStmt, const CFGBlock *Block) {
       const Stmt *S = CS->getStmt();
       if (S == DeadStmt)
         AfterDeadStmt = true;
-      if (AfterDeadStmt &&
-          // For simplicity, we only check simple coroutine statements.
-          (llvm::isa<CoreturnStmt>(S) || llvm::isa<CoroutineSuspendExpr>(S))) {
-        CoroStmt = S;
+      if (AfterDeadStmt && llvm::isa<Ts...>(S)) {
+        TargetStmt = S;
         break;
       }
     }
-  if (!CoroStmt)
+  if (!TargetStmt)
     return false;
   struct Checker : DynamicRecursiveASTVisitor {
     const Stmt *DeadStmt;
-    bool CoroutineSubStmt = false;
-    Checker(const Stmt *S) : DeadStmt(S) {
-      // Statements captured in the CFG can be implicit.
-      ShouldVisitImplicitCode = true;
-    }
+    bool IsSubStmtOfTargetStmt = false;
+    Checker(const Stmt *S) : DeadStmt(S) { ShouldVisitImplicitCode = true; }
 
     bool VisitStmt(Stmt *S) override {
       if (S == DeadStmt)
-        CoroutineSubStmt = true;
+        IsSubStmtOfTargetStmt = true;
       return true;
     }
   };
   Checker checker(DeadStmt);
-  checker.TraverseStmt(const_cast<Stmt *>(CoroStmt));
-  return checker.CoroutineSubStmt;
+  checker.TraverseStmt(const_cast<Stmt *>(TargetStmt));
+  return checker.IsSubStmtOfTargetStmt;
 }
 
 static bool isValidDeadStmt(const Stmt *S, const clang::CFGBlock *Block) {
@@ -503,7 +499,12 @@ static bool isValidDeadStmt(const Stmt *S, const clang::CFGBlock *Block) {
   // Coroutine statements are never considered dead statements, because removing
   // them may change the function semantic if it is the only coroutine statement
   // of the coroutine.
-  return !isInCoroutineStmt(S, Block);
+  //
+  // If the dead stmt is a sub-stmt of CXXDefaultInitExpr and CXXDefaultArgExpr,
+  // we would rather expect to find CXXDefaultInitExpr and CXXDefaultArgExpr as
+  // a valid dead stmt.
+  return !isDeadStmtInOneOf<CoreturnStmt, CoroutineSuspendExpr,
+                            CXXDefaultArgExpr, CXXDefaultInitExpr>(S, Block);
 }
 
 const Stmt *DeadCodeScan::findDeadCode(const clang::CFGBlock *Block) {

clang/lib/Sema/SemaExpr.cpp

@@ -5570,8 +5570,10 @@ ExprResult Sema::BuildCXXDefaultArgExpr(SourceLocation CallLoc,
           /*SkipImmediateInvocations=*/NestedDefaultChecking))
     return ExprError();
 
+  Expr *RewrittenExpr = (Init == Param->getDefaultArg() ? nullptr : Init);
   return CXXDefaultArgExpr::Create(Context, InitializationContext->Loc, Param,
-                                   Init, InitializationContext->Context);
+                                   RewrittenExpr,
+                                   InitializationContext->Context);
 }
 
 static FieldDecl *FindFieldDeclInstantiationPattern(const ASTContext &Ctx,
@@ -5689,10 +5691,11 @@ ExprResult Sema::BuildCXXDefaultInitExpr(SourceLocation Loc, FieldDecl *Field) {
       return ExprError();
     }
     Init = Res.get();
-
+    Expr *RewrittenInit =
+        (Init == Field->getInClassInitializer() ? nullptr : Init);
     return CXXDefaultInitExpr::Create(Context, InitializationContext->Loc,
                                       Field, InitializationContext->Context,
-                                      Init);
+                                      RewrittenInit);
   }
 
   // DR1351:

clang/lib/StaticAnalyzer/Core/ExprEngine.cpp

@@ -1991,33 +1991,45 @@ void ExprEngine::Visit(const Stmt *S, ExplodedNode *Pred,
       ExplodedNodeSet Tmp;
       StmtNodeBuilder Bldr2(PreVisit, Tmp, *currBldrCtx);
 
-      const Expr *ArgE;
-      if (const auto *DefE = dyn_cast<CXXDefaultArgExpr>(S))
+      bool HasRebuiltInit = false;
+      const Expr *ArgE = nullptr;
+      if (const auto *DefE = dyn_cast<CXXDefaultArgExpr>(S)) {
         ArgE = DefE->getExpr();
-      else if (const auto *DefE = dyn_cast<CXXDefaultInitExpr>(S))
+        HasRebuiltInit = DefE->hasRewrittenInit();
+      } else if (const auto *DefE = dyn_cast<CXXDefaultInitExpr>(S)) {
         ArgE = DefE->getExpr();
-      else
+        HasRebuiltInit = DefE->hasRewrittenInit();
+      } else
         llvm_unreachable("unknown constant wrapper kind");
 
-      bool IsTemporary = false;
-      if (const auto *MTE = dyn_cast<MaterializeTemporaryExpr>(ArgE)) {
-        ArgE = MTE->getSubExpr();
-        IsTemporary = true;
-      }
+      if (HasRebuiltInit) {
+        for (auto *N : PreVisit) {
+          ProgramStateRef state = N->getState();
+          const LocationContext *LCtx = N->getLocationContext();
+          state = state->BindExpr(S, LCtx, state->getSVal(ArgE, LCtx));
+          Bldr2.generateNode(S, N, state);
+        }
+      } else {
+        // If it's not rewritten, the contents of these expressions are not
+        // actually part of the current function, so we fall back to constant
+        // evaluation.
+        bool IsTemporary = false;
+        if (const auto *MTE = dyn_cast<MaterializeTemporaryExpr>(ArgE)) {
+          ArgE = MTE->getSubExpr();
+          IsTemporary = true;
+        }
+
+        std::optional<SVal> ConstantVal = svalBuilder.getConstantVal(ArgE);
+        const LocationContext *LCtx = Pred->getLocationContext();
+        for (auto *I : PreVisit) {
+          ProgramStateRef State = I->getState();
+          State = State->BindExpr(S, LCtx, ConstantVal.value_or(UnknownVal()));
+          if (IsTemporary)
+            State = createTemporaryRegionIfNeeded(State, LCtx, cast<Expr>(S),
+                                                  cast<Expr>(S));
 
-      std::optional<SVal> ConstantVal = svalBuilder.getConstantVal(ArgE);
-      if (!ConstantVal)
-        ConstantVal = UnknownVal();
-
-      const LocationContext *LCtx = Pred->getLocationContext();
-      for (const auto I : PreVisit) {
-        ProgramStateRef State = I->getState();
-        State = State->BindExpr(S, LCtx, *ConstantVal);
-        if (IsTemporary)
-          State = createTemporaryRegionIfNeeded(State, LCtx,
-                                                cast<Expr>(S),
-                                                cast<Expr>(S));
-        Bldr2.generateNode(S, I, State);
+          Bldr2.generateNode(S, I, State);
+        }
       }
 
       getCheckerManager().runCheckersForPostStmt(Dst, Tmp, S, *this);

clang/test/AST/ast-dump-recovery.cpp

@@ -507,7 +507,7 @@ union U {
 // CHECK-NEXT:      `-DeclStmt {{.*}}
 // CHECK-NEXT:        `-VarDecl {{.*}} g 'U':'GH112560::U' listinit
 // CHECK-NEXT:          `-InitListExpr {{.*}} 'U':'GH112560::U' contains-errors field Field {{.*}} 'f' 'int'
-// CHECK-NEXT:            `-CXXDefaultInitExpr {{.*}} 'int' contains-errors has rewritten init
+// CHECK-NEXT:            `-CXXDefaultInitExpr {{.*}} 'int' contains-errors
 // CHECK-NEXT:              `-RecoveryExpr {{.*}} 'int' contains-errors
 // DISABLED-NOT: -RecoveryExpr {{.*}} contains-errors
 void foo() {

clang/test/Analysis/lifetime-extended-regions.cpp

@@ -121,11 +121,10 @@ void aggregateWithReferences() {
   clang_analyzer_dump(viaReference.rx); // expected-warning-re {{&lifetime_extended_object{int, viaReference, S{{[0-9]+}}} }}
   clang_analyzer_dump(viaReference.ry); // expected-warning-re {{&lifetime_extended_object{Composite, viaReference, S{{[0-9]+}}} }}
 
-  // FIXME: clang currently support extending lifetime of object bound to reference members of aggregates,
-  // that are created from default member initializer. But CFG and ExprEngine need to be updated to address this change.
-  // The following expect warning: {{&lifetime_extended_object{Composite, defaultInitExtended, S{{[0-9]+}}} }}
+  // The lifetime of object bound to reference members of aggregates,
+  // that are created from default member initializer was extended.
   RefAggregate defaultInitExtended{i};
-  clang_analyzer_dump(defaultInitExtended.ry); // expected-warning {{Unknown }}
+  clang_analyzer_dump(defaultInitExtended.ry); // expected-warning-re {{&lifetime_extended_object{Composite, defaultInitExtended, S{{[0-9]+}}} }}
 }
 
 void lambda() {

clang/test/SemaCXX/cxx2c-placeholder-vars.cpp

@@ -274,16 +274,16 @@ void f() {
 // CHECK: ClassTemplateSpecializationDecl {{.*}} struct A definition
 // CHECK: CXXConstructorDecl {{.*}} implicit used constexpr A 'void () noexcept'
 // CHECK-NEXT: CXXCtorInitializer Field {{.*}} '_' 'int'
-// CHECK-NEXT: CXXDefaultInitExpr {{.*}} 'int' has rewritten init
+// CHECK-NEXT: CXXDefaultInitExpr {{.*}} 'int'
 // CHECK-NEXT: IntegerLiteral {{.*}} 'int' 1
 // CHECK-NEXT: CXXCtorInitializer Field {{.*}} '_' 'int'
-// CHECK-NEXT: CXXDefaultInitExpr {{.*}} 'int' has rewritten init
+// CHECK-NEXT: CXXDefaultInitExpr {{.*}} 'int'
 // CHECK-NEXT: IntegerLiteral {{.*}} 'int' 2
 // CHECK-NEXT: CXXCtorInitializer Field {{.*}} 'a' 'int'
-// CHECK-NEXT: CXXDefaultInitExpr {{.*}} 'int' has rewritten init
+// CHECK-NEXT: CXXDefaultInitExpr {{.*}} 'int'
 // CHECK-NEXT: IntegerLiteral {{.*}} 'int' 3
 // CHECK-NEXT: CXXCtorInitializer Field {{.*}} '_' 'int'
-// CHECK-NEXT: CXXDefaultInitExpr {{.*}} 'int' has rewritten init
+// CHECK-NEXT: CXXDefaultInitExpr {{.*}} 'int'
 // CHECK-NEXT: IntegerLiteral {{.*}} 'int' 4
 // CHECK-NEXT: CompoundStmt {{.*}}
 

clang/test/SemaCXX/warn-unreachable.cpp

@@ -414,3 +414,42 @@ void tautological_compare(bool x, int y) {
     calledFun();
 
 }
+
+namespace test_rebuilt_default_arg {
+struct A {
+  explicit A(int = __builtin_LINE());
+};
+
+int h(int a) {
+  return 3;
+  A();  // expected-warning {{will never be executed}}
+}
+
+struct Temp {
+  Temp();
+  ~Temp();
+};
+
+struct B {
+  explicit B(const Temp &t = Temp());
+};
+int f(int a) {
+  return 3;
+  B();  // expected-warning {{will never be executed}}
+}
+} // namespace test_rebuilt_default_arg
+namespace test_rebuilt_default_init {
+
+struct A {
+  A();
+  ~A();
+};
+
+struct B {
+  const A &t = A();
+};
+int f(int a) {
+  return 3;
+  A{};  // expected-warning {{will never be executed}}
+}
+} // namespace test_rebuilt_default_init