1 //===- ConstructionContext.cpp - CFG constructor information --------------===//
2 //
3 //                     The LLVM Compiler Infrastructure
4 //
5 // This file is distributed under the University of Illinois Open Source
6 // License. See LICENSE.TXT for details.
7 //
8 //===----------------------------------------------------------------------===//
9 //
10 // This file defines the ConstructionContext class and its sub-classes,
11 // which represent various different ways of constructing C++ objects
12 // with the additional information the users may want to know about
13 // the constructor.
14 //
15 //===----------------------------------------------------------------------===//
16 
17 #include "clang/Analysis/ConstructionContext.h"
18 
19 using namespace clang;
20 
21 const ConstructionContextLayer *
22 ConstructionContextLayer::create(BumpVectorContext &C, TriggerTy Trigger,
23                                  const ConstructionContextLayer *Parent) {
24   ConstructionContextLayer *CC =
25       C.getAllocator().Allocate<ConstructionContextLayer>();
26   return new (CC) ConstructionContextLayer(Trigger, Parent);
27 }
28 
29 bool ConstructionContextLayer::isStrictlyMoreSpecificThan(
30     const ConstructionContextLayer *Other) const {
31   const ConstructionContextLayer *Self = this;
32   while (true) {
33     if (!Other)
34       return Self;
35     if (!Self || !Self->isSameLayer(Other))
36       return false;
37     Self = Self->getParent();
38     Other = Other->getParent();
39   }
40   llvm_unreachable("The above loop can only be terminated via return!");
41 }
42 
43 const ConstructionContext *ConstructionContext::createFromLayers(
44     BumpVectorContext &C, const ConstructionContextLayer *TopLayer) {
45   // Before this point all we've had was a stockpile of arbitrary layers.
46   // Now validate that it is shaped as one of the finite amount of expected
47   // patterns.
48   if (const Stmt *S = TopLayer->getTriggerStmt()) {
49     if (const auto *DS = dyn_cast<DeclStmt>(S)) {
50       assert(TopLayer->isLast());
51       auto *CC =
52           C.getAllocator().Allocate<SimpleVariableConstructionContext>();
53       return new (CC) SimpleVariableConstructionContext(DS);
54     } else if (const auto *NE = dyn_cast<CXXNewExpr>(S)) {
55       assert(TopLayer->isLast());
56       auto *CC =
57           C.getAllocator().Allocate<NewAllocatedObjectConstructionContext>();
58       return new (CC) NewAllocatedObjectConstructionContext(NE);
59     } else if (const auto *BTE = dyn_cast<CXXBindTemporaryExpr>(S)) {
60       const MaterializeTemporaryExpr *MTE = nullptr;
61       assert(BTE->getType().getCanonicalType()
62                 ->getAsCXXRecordDecl()->hasNonTrivialDestructor());
63       // For temporaries with destructors, there may or may not be
64       // lifetime extension on the parent layer.
65       if (const ConstructionContextLayer *ParentLayer = TopLayer->getParent()) {
66         assert(ParentLayer->isLast());
67         if ((MTE = dyn_cast<MaterializeTemporaryExpr>(
68                  ParentLayer->getTriggerStmt()))) {
69           // A temporary object which has both destruction and
70           // materialization info.
71           auto *CC =
72               C.getAllocator().Allocate<TemporaryObjectConstructionContext>();
73           return new (CC) TemporaryObjectConstructionContext(BTE, MTE);
74         }
75         // C++17 *requires* elision of the constructor at the return site
76         // and at variable initialization site, while previous standards
77         // were allowing an optional elidable constructor.
78         if (auto *RS = dyn_cast<ReturnStmt>(ParentLayer->getTriggerStmt())) {
79           assert(!RS->getRetValue()->getType().getCanonicalType()
80                     ->getAsCXXRecordDecl()->hasTrivialDestructor());
81           auto *CC =
82               C.getAllocator()
83                   .Allocate<
84                       CXX17ElidedCopyReturnedValueConstructionContext>();
85           return new (CC)
86               CXX17ElidedCopyReturnedValueConstructionContext(RS, BTE);
87         }
88         if (auto *DS = dyn_cast<DeclStmt>(ParentLayer->getTriggerStmt())) {
89           assert(!cast<VarDecl>(DS->getSingleDecl())->getType()
90                       .getCanonicalType()->getAsCXXRecordDecl()
91                       ->hasTrivialDestructor());
92           auto *CC =
93               C.getAllocator()
94                   .Allocate<CXX17ElidedCopyVariableConstructionContext>();
95           return new (CC) CXX17ElidedCopyVariableConstructionContext(DS, BTE);
96         }
97         llvm_unreachable("Unexpected construction context with destructor!");
98       }
99       // A temporary object that doesn't require materialization.
100       auto *CC =
101           C.getAllocator().Allocate<TemporaryObjectConstructionContext>();
102       return new (CC)
103           TemporaryObjectConstructionContext(BTE, /*MTE=*/nullptr);
104     } else if (const auto *MTE = dyn_cast<MaterializeTemporaryExpr>(S)) {
105       // If the object requires destruction and is not lifetime-extended,
106       // then it must have a BTE within its MTE.
107       assert(MTE->getType().getCanonicalType()
108                 ->getAsCXXRecordDecl()->hasTrivialDestructor() ||
109              MTE->getStorageDuration() != SD_FullExpression);
110       assert(TopLayer->isLast());
111       auto *CC =
112           C.getAllocator().Allocate<TemporaryObjectConstructionContext>();
113       return new (CC) TemporaryObjectConstructionContext(nullptr, MTE);
114     } else if (const auto *RS = dyn_cast<ReturnStmt>(S)) {
115       assert(TopLayer->isLast());
116       auto *CC =
117           C.getAllocator().Allocate<SimpleReturnedValueConstructionContext>();
118       return new (CC) SimpleReturnedValueConstructionContext(RS);
119     }
120   } else if (const CXXCtorInitializer *I = TopLayer->getTriggerInit()) {
121     assert(TopLayer->isLast());
122     auto *CC =
123         C.getAllocator().Allocate<ConstructorInitializerConstructionContext>();
124     return new (CC) ConstructorInitializerConstructionContext(I);
125   }
126   llvm_unreachable("Unexpected construction context!");
127 }
128