[CFG] [analyzer] Recall that we only skip NoOp casts in construction contexts.

haoNoQ · haoNoQ · commit 6603052235bd · 2018-03-01T01:09:24.000Z
For now. We should also add support for ConstructorConversion casts as presented in the attached test case, but this requires more changes because AST around them seems different. The check was originally present but was accidentally lost during r326021. Differential Revision: https://reviews.llvm.org/D43840 llvm-svn: 326402
diff --git a/clang/lib/Analysis/CFG.cpp b/clang/lib/Analysis/CFG.cpp
@@ -1200,7 +1200,9 @@ void CFGBuilder::findConstructionContexts(
   }
   case Stmt::ImplicitCastExprClass: {
     auto *Cast = cast<ImplicitCastExpr>(Child);
-    findConstructionContexts(Layer, Cast->getSubExpr());
+    // TODO: We need to support CK_ConstructorConversion, maybe other kinds?
+    if (Cast->getCastKind() == CK_NoOp)
+      findConstructionContexts(Layer, Cast->getSubExpr());
     break;
   }
   case Stmt::CXXBindTemporaryExprClass: {
diff --git a/clang/test/Analysis/cfg-rich-constructors.cpp b/clang/test/Analysis/cfg-rich-constructors.cpp
@@ -484,4 +484,35 @@ void referenceWithFunctionalCast() {
 void constructorInTernaryCondition() {
   const D &d = D(1) ? D(2) : D(3);
 }
+
 } // end namespace temporary_object_expr_with_dtors
+
+namespace implicit_constructor_conversion {
+
+class A {};
+A get();
+
+class B {
+public:
+  B(const A &);
+  ~B() {}
+};
+
+// FIXME: Find construction context for the implicit constructor conversion.
+// CHECK: void implicitConstructionConversionFromFunctionValue()
+// CHECK:          1: get
+// CHECK-NEXT:     2: [B1.1] (ImplicitCastExpr, FunctionToPointerDecay, class implicit_constructor_conver
+// CHECK-NEXT:     3: [B1.2]()
+// CHECK-NEXT:     4: [B1.3] (ImplicitCastExpr, NoOp, const class implicit_constructor_conversion::A)
+// CHECK-NEXT:     5: [B1.4]
+// CHECK-NEXT:     6: [B1.5] (CXXConstructExpr, class implicit_constructor_conversion::B)
+// CHECK-NEXT:     7: [B1.6] (ImplicitCastExpr, ConstructorConversion, class implicit_constructor_convers
+// CHECK-NEXT:     8: [B1.7] (ImplicitCastExpr, NoOp, const class implicit_constructor_conversion::B)
+// CHECK-NEXT:     9: [B1.8]
+// CHECK-NEXT:    10: const implicit_constructor_conversion::B &b = get();
+// CHECK-NEXT:    11: [B1.10].~B() (Implicit destructor)
+void implicitConstructionConversionFromFunctionValue() {
+  const B &b = get(); // no-crash
+}
+
+} // end namespace implicit_constructor_conversion

Original file line number	Diff line number	Diff line change
`@@ -1200,7 +1200,9 @@ void CFGBuilder::findConstructionContexts(`
`1200`	`1200`	`}`
`1201`	`1201`	`case Stmt::ImplicitCastExprClass: {`
`1202`	`1202`	`auto *Cast = cast<ImplicitCastExpr>(Child);`
`1203`		`- findConstructionContexts(Layer, Cast->getSubExpr());`
	`1203`	`+ // TODO: We need to support CK_ConstructorConversion, maybe other kinds?`
	`1204`	`+ if (Cast->getCastKind() == CK_NoOp)`
	`1205`	`+ findConstructionContexts(Layer, Cast->getSubExpr());`
`1204`	`1206`	`break;`
`1205`	`1207`	`}`
`1206`	`1208`	`case Stmt::CXXBindTemporaryExprClass: {`