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
24using namespace clang;
25using namespace ento;
26
27namespace {
28class UndefCapturedBlockVarChecker
29 : public Checker< check::PostStmt<BlockExpr> > {
30 const BugType BT{this, "uninitialized variable captured by block"};
31
32public:
33 void checkPostStmt(const BlockExpr *BE, CheckerContext &C) const;
34};
35} // end anonymous namespace
36
37static const DeclRefExpr *FindBlockDeclRefExpr(const Stmt *S,
38 const VarDecl *VD) {
39 if (const DeclRefExpr *BR = dyn_cast<DeclRefExpr>(Val: 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(S: Child, VD))
46 return BR;
47
48 return nullptr;
49}
50
51void
52UndefCapturedBlockVarChecker::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>(Val: C.getSVal(S: 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(R: Var.getOriginalRegion()).getAs<UndefinedVal>()) {
72 if (ExplodedNode *N = C.generateErrorNode()) {
73 // Generate a bug report.
74 SmallString<128> buf;
75 llvm::raw_svector_ostream os(buf);
76
77 os << "Variable '" << VD->getName()
78 << "' is uninitialized when captured by block";
79
80 auto R = std::make_unique<PathSensitiveBugReport>(args: BT, args: os.str(), args&: N);
81 if (const Expr *Ex = FindBlockDeclRefExpr(S: BE->getBody(), VD))
82 R->addRange(R: Ex->getSourceRange());
83 bugreporter::trackStoredValue(V: *V, R: VR, Report&: *R,
84 Opts: {.Kind: bugreporter::TrackingKind::Thorough,
85 /*EnableNullFPSuppression*/ false});
86 R->disablePathPruning();
87 // need location of block
88 C.emitReport(R: std::move(R));
89 }
90 }
91 }
92}
93
94void ento::registerUndefCapturedBlockVarChecker(CheckerManager &mgr) {
95 mgr.registerChecker<UndefCapturedBlockVarChecker>();
96}
97
98bool ento::shouldRegisterUndefCapturedBlockVarChecker(const CheckerManager &mgr) {
99 return true;
100}
101