[CFG] Provide construction contexts for return value constructors.

When the current function returns a C++ object by value, CFG elements for constructors that construct the return values can now be queried to discover that they're indeed participating in construction of the respective return value at the respective return statement. Differential Revision: https://reviews.llvm.org/D42875 llvm-svn: 324952
llvm · Feb 12, 2018 · 9ac2e11 · 9ac2e11
1 parent 005e7c3
commit 9ac2e11
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Showing 3 changed files with 98 additions and 2 deletions.
diff --git a/clang/lib/Analysis/CFG.cpp b/clang/lib/Analysis/CFG.cpp
@@ -2575,6 +2575,8 @@ CFGBlock *CFGBuilder::VisitReturnStmt(ReturnStmt *R) {
 
   addAutomaticObjHandling(ScopePos, LocalScope::const_iterator(), R);
 
+  EnterConstructionContextIfNecessary(R, R->getRetValue());
+
   // If the one of the destructors does not return, we already have the Exit
   // block as a successor.
   if (!Block->hasNoReturnElement())

diff --git a/clang/test/Analysis/cfg-rich-constructors.cpp b/clang/test/Analysis/cfg-rich-constructors.cpp
@@ -5,6 +5,7 @@ class C {
 public:
   C();
   C(C *);
+  C(int, int);
 
   static C get();
 };
@@ -224,3 +225,94 @@ class D: public C {
 };
 
 } // end namespace ctor_initializers
+
+namespace return_stmt {
+
+// CHECK: C returnVariable()
+// CHECK:          1:  (CXXConstructExpr, [B1.2], class C)
+// CHECK-NEXT:     2: C c;
+// CHECK-NEXT:     3: c
+// CHECK-NEXT:     4: [B1.3] (ImplicitCastExpr, NoOp, class C)
+// CHECK-NEXT:     5: [B1.4] (CXXConstructExpr, [B1.6], class C)
+// CHECK-NEXT:     6: return [B1.5];
+C returnVariable() {
+  C c;
+  return c;
+}
+
+// CHECK: C returnEmptyBraces()
+// CHECK:          1: {} (CXXConstructExpr, [B1.2], class C)
+// CHECK-NEXT:     2: return [B1.1];
+C returnEmptyBraces() {
+  return {};
+}
+
+// CHECK: C returnBracesWithOperatorNew()
+// CHECK:          1: CFGNewAllocator(C *)
+// CHECK-NEXT:     2:  (CXXConstructExpr, [B1.3], class C)
+// CHECK-NEXT:     3: new C([B1.2])
+// CHECK-NEXT:     4: {[B1.3]} (CXXConstructExpr, [B1.5], class C)
+// CHECK-NEXT:     5: return [B1.4];
+C returnBracesWithOperatorNew() {
+  return {new C()};
+}
+
+// CHECK: C returnBracesWithMultipleItems()
+// CHECK:          1: 123
+// CHECK-NEXT:     2: 456
+// CHECK-NEXT:     3: {[B1.1], [B1.2]} (CXXConstructExpr, [B1.4], class C)
+// CHECK-NEXT:     4: return [B1.3];
+C returnBracesWithMultipleItems() {
+  return {123, 456};
+}
+
+// TODO: Should find construction targets for the first constructor as well.
+// CHECK: C returnTemporary()
+// CHECK:          1: C() (CXXConstructExpr, class C)
+// CHECK-NEXT:     2: [B1.1]
+// CHECK-NEXT:     3: [B1.2] (CXXConstructExpr, [B1.4], class C)
+// CHECK-NEXT:     4: return [B1.3];
+C returnTemporary() {
+  return C();
+}
+
+// TODO: Should find construction targets for the first constructor as well.
+// CHECK: C returnTemporaryWithArgument()
+// CHECK:          1: nullptr
+// CHECK-NEXT:     2: [B1.1] (ImplicitCastExpr, NullToPointer, class C *)
+// CHECK-NEXT:     3: [B1.2] (CXXConstructExpr, class C)
+// CHECK-NEXT:     4: C([B1.3]) (CXXFunctionalCastExpr, ConstructorConversion, class C)
+// CHECK-NEXT:     5: [B1.4]
+// CHECK-NEXT:     6: [B1.5] (CXXConstructExpr, [B1.7], class C)
+// CHECK-NEXT:     7: return [B1.6];
+C returnTemporaryWithArgument() {
+  return C(nullptr);
+}
+
+// CHECK: C returnTemporaryConstructedByFunction()
+// CHECK:          1: C::get
+// CHECK-NEXT:     2: [B1.1] (ImplicitCastExpr, FunctionToPointerDecay, class C (*)(void))
+// CHECK-NEXT:     3: [B1.2]()
+// CHECK-NEXT:     4: [B1.3]
+// CHECK-NEXT:     5: [B1.4] (CXXConstructExpr, [B1.6], class C)
+// CHECK-NEXT:     6: return [B1.5];
+C returnTemporaryConstructedByFunction() {
+  return C::get();
+}
+
+// TODO: Should find construction targets for the first constructor as well.
+// CHECK: C returnChainOfCopies()
+// CHECK:          1: C::get
+// CHECK-NEXT:     2: [B1.1] (ImplicitCastExpr, FunctionToPointerDecay, class C (*)(void))
+// CHECK-NEXT:     3: [B1.2]()
+// CHECK-NEXT:     4: [B1.3]
+// CHECK-NEXT:     5: [B1.4] (CXXConstructExpr, class C)
+// CHECK-NEXT:     6: C([B1.5]) (CXXFunctionalCastExpr, ConstructorConversion, class C)
+// CHECK-NEXT:     7: [B1.6]
+// CHECK-NEXT:     8: [B1.7] (CXXConstructExpr, [B1.9], class C)
+// CHECK-NEXT:     9: return [B1.8];
+C returnChainOfCopies() {
+  return C(C::get());
+}
+
+} // end namespace return_stmt
diff --git a/clang/test/Analysis/temp-obj-dtors-cfg-output.cpp b/clang/test/Analysis/temp-obj-dtors-cfg-output.cpp
@@ -220,7 +220,8 @@ int testConsistencyNestedNormalReturn(bool value) {
 // CHECK:     2: [B1.1] (BindTemporary)
 // CHECK:     3: [B1.2] (ImplicitCastExpr, NoOp, const class A)
 // CHECK:     4: [B1.3]
-// CHECK:     5: [B1.4] (CXXConstructExpr, class A)
+// WARNINGS:     5: [B1.4] (CXXConstructExpr, class A)
+// ANALYZER:     5: [B1.4] (CXXConstructExpr, [B1.7], class A)
 // CHECK:     6: ~A() (Temporary object destructor)
 // CHECK:     7: return [B1.5];
 // CHECK:     Preds (1): B2
@@ -278,7 +279,8 @@ int testConsistencyNestedNormalReturn(bool value) {
 // CHECK:     2: [B1.1] (BindTemporary)
 // CHECK:     3: [B1.2] (ImplicitCastExpr, NoOp, const class A)
 // CHECK:     4: [B1.3]
-// CHECK:     5: [B1.4] (CXXConstructExpr, class A)
+// WARNINGS:     5: [B1.4] (CXXConstructExpr, class A)
+// ANALYZER:     5: [B1.4] (CXXConstructExpr, [B1.7], class A)
 // CHECK:     6: ~A() (Temporary object destructor)
 // CHECK:     7: return [B1.5];
 // CHECK:     Preds (1): B2