[CFG] [analyzer] Add construction context for ReturnStmt.

[NoQ]

Summary

This one's new, the analyzer didn't enjoy this before. This patch adds construction context for ReturnStmt, which means that we'd be able to properly return objects from functions by value.

This is the CFG part of the work, the Analyzer-side improvement to make use of it will be in the next patch.

[NoQ]

Add a test in which we return a variable.

[NoQ]

rC325202 is attached to this revision accidentally; it should have been attached to D42876.

cfe/trunk/lib/Analysis/CFG.cpp

CFGBlock *CFGBuilder::VisitReturnStmt(ReturnStmt *R) {
   //       for that code; a simple "mark-and-sweep" from the entry block will be
   //       able to report such dead blocks.
 
   // Create the new block.
   Block = createBlock(false);
 
   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())
     addSuccessor(Block, &cfg->getExit());
 
   // Add the return statement to the block.  This may create new blocks if R
   // contains control-flow (short-circuit operations).
   return VisitStmt(R, AddStmtChoice::AlwaysAdd);

cfe/trunk/test/Analysis/cfg-rich-constructors.cpp

 // RUN: %clang_analyze_cc1 -analyzer-checker=debug.DumpCFG -triple x86_64-apple-darwin12 -analyzer-config cfg-temporary-dtors=true -std=c++11 %s > %t 2>&1
 // RUN: FileCheck --input-file=%t %s
 
 class C {
 public:
   C();
   C(C *);
+  C(int, int);
 
   static C get();
 };
 
 typedef __typeof(sizeof(int)) size_t;
 void *operator new(size_t size, void *placement);
 
 namespace operator_new {

 // CHECK-NEXT:    12: [B1.11] (CXXConstructExpr, [B1.13], class C)
 // CHECK-NEXT:    13: new C([B1.12])
 // CHECK-NEXT:    14: [B1.13] (CXXConstructExpr, c1([B1.13]) (Member initializer), class C)
 // CHECK-NEXT:    15: c1([B1.14]) (Member initializer)
   D(double): C(C::get()), c1(new C(C::get())) {}
 };
 
 } // 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

cfe/trunk/test/Analysis/temp-obj-dtors-cfg-output.cpp

 // CHECK:     Preds (1): B1
 // CHECK:   [B2 (ENTRY)]
 // CHECK:     Succs (1): B1
 // CHECK:   [B1]
 // CHECK:     1: A() (CXXConstructExpr, class A)
 // 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
 // CHECK:     Succs (1): B0
 // CHECK:   [B0 (EXIT)]
 // CHECK:     Preds (1): B1
 // CHECK:   [B2 (ENTRY)]
 // CHECK:     Succs (1): B1

 // CHECK:     Preds (1): B1
 // CHECK:   [B2 (ENTRY)]
 // CHECK:     Succs (1): B1
 // CHECK:   [B1]
 // CHECK:     1: A() (CXXConstructExpr, class A)
 // 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
 // CHECK:     Succs (1): B0
 // CHECK:   [B0 (EXIT)]
 // CHECK:     Preds (1): B1
 // CHECK:   [B2 (ENTRY)]
 // CHECK:     Succs (1): B1