1 // UndefCapturedBlockVarChecker.cpp - Uninitialized captured vars -*- C++ -*-=//
2 //
3 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
4 // See https://llvm.org/LICENSE.txt for license information.
5 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
6 //
7 //===----------------------------------------------------------------------===//
8 //
9 // This checker detects blocks that capture uninitialized values.
10 //
11 //===----------------------------------------------------------------------===//
12 
13 #include "clang/StaticAnalyzer/Checkers/BuiltinCheckerRegistration.h"
14 #include "clang/AST/Attr.h"
15 #include "clang/StaticAnalyzer/Core/BugReporter/BugType.h"
16 #include "clang/StaticAnalyzer/Core/Checker.h"
17 #include "clang/StaticAnalyzer/Core/CheckerManager.h"
18 #include "clang/StaticAnalyzer/Core/PathSensitive/CheckerContext.h"
19 #include "clang/StaticAnalyzer/Core/PathSensitive/ExprEngine.h"
20 #include "llvm/ADT/SmallString.h"
21 #include "llvm/Support/raw_ostream.h"
22 #include <optional>
23 
24 using namespace clang;
25 using namespace ento;
26 
27 namespace {
28 class UndefCapturedBlockVarChecker
29   : public Checker< check::PostStmt<BlockExpr> > {
30   mutable std::unique_ptr<BugType> BT;
31 
32 public:
33   void checkPostStmt(const BlockExpr *BE, CheckerContext &C) const;
34 };
35 } // end anonymous namespace
36 
37 static const DeclRefExpr *FindBlockDeclRefExpr(const Stmt *S,
38                                                const VarDecl *VD) {
39   if (const DeclRefExpr *BR = dyn_cast<DeclRefExpr>(S))
40     if (BR->getDecl() == VD)
41       return BR;
42 
43   for (const Stmt *Child : S->children())
44     if (Child)
45       if (const DeclRefExpr *BR = FindBlockDeclRefExpr(Child, VD))
46         return BR;
47 
48   return nullptr;
49 }
50 
51 void
52 UndefCapturedBlockVarChecker::checkPostStmt(const BlockExpr *BE,
53                                             CheckerContext &C) const {
54   if (!BE->getBlockDecl()->hasCaptures())
55     return;
56 
57   ProgramStateRef state = C.getState();
58   auto *R = cast<BlockDataRegion>(C.getSVal(BE).getAsRegion());
59 
60   for (auto Var : R->referenced_vars()) {
61     // This VarRegion is the region associated with the block; we need
62     // the one associated with the encompassing context.
63     const VarRegion *VR = Var.getCapturedRegion();
64     const VarDecl *VD = VR->getDecl();
65 
66     if (VD->hasAttr<BlocksAttr>() || !VD->hasLocalStorage())
67       continue;
68 
69     // Get the VarRegion associated with VD in the local stack frame.
70     if (std::optional<UndefinedVal> V =
71             state->getSVal(Var.getOriginalRegion()).getAs<UndefinedVal>()) {
72       if (ExplodedNode *N = C.generateErrorNode()) {
73         if (!BT)
74           BT.reset(
75               new BuiltinBug(this, "uninitialized variable captured by block"));
76 
77         // Generate a bug report.
78         SmallString<128> buf;
79         llvm::raw_svector_ostream os(buf);
80 
81         os << "Variable '" << VD->getName()
82            << "' is uninitialized when captured by block";
83 
84         auto R = std::make_unique<PathSensitiveBugReport>(*BT, os.str(), N);
85         if (const Expr *Ex = FindBlockDeclRefExpr(BE->getBody(), VD))
86           R->addRange(Ex->getSourceRange());
87         bugreporter::trackStoredValue(*V, VR, *R,
88                                       {bugreporter::TrackingKind::Thorough,
89                                        /*EnableNullFPSuppression*/ false});
90         R->disablePathPruning();
91         // need location of block
92         C.emitReport(std::move(R));
93       }
94     }
95   }
96 }
97 
98 void ento::registerUndefCapturedBlockVarChecker(CheckerManager &mgr) {
99   mgr.registerChecker<UndefCapturedBlockVarChecker>();
100 }
101 
102 bool ento::shouldRegisterUndefCapturedBlockVarChecker(const CheckerManager &mgr) {
103   return true;
104 }
105