1//=== LLVMConventionsChecker.cpp - Check LLVM codebase conventions ---*- 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 defines LLVMConventionsChecker, a bunch of small little checks
10// for checking specific coding conventions in the LLVM/Clang codebase.
11//
12//===----------------------------------------------------------------------===//
13
14#include "clang/StaticAnalyzer/Checkers/BuiltinCheckerRegistration.h"
15#include "clang/AST/DeclTemplate.h"
16#include "clang/AST/StmtVisitor.h"
17#include "clang/StaticAnalyzer/Core/BugReporter/BugReporter.h"
18#include "clang/StaticAnalyzer/Core/Checker.h"
19#include "llvm/ADT/SmallString.h"
20#include "llvm/Support/raw_ostream.h"
21
22using namespace clang;
23using namespace ento;
24
25//===----------------------------------------------------------------------===//
26// Generic type checking routines.
27//===----------------------------------------------------------------------===//
28
29static bool IsLLVMStringRef(QualType T) {
30 const RecordType *RT = T->getAs<RecordType>();
31 if (!RT)
32 return false;
33
34 return StringRef(QualType(RT, 0).getAsString()) == "class StringRef";
35}
36
37/// Check whether the declaration is semantically inside the top-level
38/// namespace named by ns.
39static bool InNamespace(const Decl *D, StringRef NS) {
40 const NamespaceDecl *ND = dyn_cast<NamespaceDecl>(Val: D->getDeclContext());
41 if (!ND)
42 return false;
43 const IdentifierInfo *II = ND->getIdentifier();
44 if (!II || II->getName() != NS)
45 return false;
46 return isa<TranslationUnitDecl>(Val: ND->getDeclContext());
47}
48
49static bool IsStdString(QualType T) {
50 if (const ElaboratedType *QT = T->getAs<ElaboratedType>())
51 T = QT->getNamedType();
52
53 const TypedefType *TT = T->getAs<TypedefType>();
54 if (!TT)
55 return false;
56
57 const TypedefNameDecl *TD = TT->getDecl();
58
59 if (!TD->isInStdNamespace())
60 return false;
61
62 return TD->getName() == "string";
63}
64
65static bool IsClangType(const RecordDecl *RD) {
66 return RD->getName() == "Type" && InNamespace(D: RD, NS: "clang");
67}
68
69static bool IsClangDecl(const RecordDecl *RD) {
70 return RD->getName() == "Decl" && InNamespace(D: RD, NS: "clang");
71}
72
73static bool IsClangStmt(const RecordDecl *RD) {
74 return RD->getName() == "Stmt" && InNamespace(D: RD, NS: "clang");
75}
76
77static bool IsClangAttr(const RecordDecl *RD) {
78 return RD->getName() == "Attr" && InNamespace(D: RD, NS: "clang");
79}
80
81static bool IsStdVector(QualType T) {
82 const TemplateSpecializationType *TS = T->getAs<TemplateSpecializationType>();
83 if (!TS)
84 return false;
85
86 TemplateName TM = TS->getTemplateName();
87 TemplateDecl *TD = TM.getAsTemplateDecl();
88
89 if (!TD || !InNamespace(D: TD, NS: "std"))
90 return false;
91
92 return TD->getName() == "vector";
93}
94
95static bool IsSmallVector(QualType T) {
96 const TemplateSpecializationType *TS = T->getAs<TemplateSpecializationType>();
97 if (!TS)
98 return false;
99
100 TemplateName TM = TS->getTemplateName();
101 TemplateDecl *TD = TM.getAsTemplateDecl();
102
103 if (!TD || !InNamespace(D: TD, NS: "llvm"))
104 return false;
105
106 return TD->getName() == "SmallVector";
107}
108
109//===----------------------------------------------------------------------===//
110// CHECK: a StringRef should not be bound to a temporary std::string whose
111// lifetime is shorter than the StringRef's.
112//===----------------------------------------------------------------------===//
113
114namespace {
115class StringRefCheckerVisitor : public StmtVisitor<StringRefCheckerVisitor> {
116 const Decl *DeclWithIssue;
117 BugReporter &BR;
118 const CheckerBase *Checker;
119
120public:
121 StringRefCheckerVisitor(const Decl *declWithIssue, BugReporter &br,
122 const CheckerBase *checker)
123 : DeclWithIssue(declWithIssue), BR(br), Checker(checker) {}
124 void VisitChildren(Stmt *S) {
125 for (Stmt *Child : S->children())
126 if (Child)
127 Visit(S: Child);
128 }
129 void VisitStmt(Stmt *S) { VisitChildren(S); }
130 void VisitDeclStmt(DeclStmt *DS);
131private:
132 void VisitVarDecl(VarDecl *VD);
133};
134} // end anonymous namespace
135
136static void CheckStringRefAssignedTemporary(const Decl *D, BugReporter &BR,
137 const CheckerBase *Checker) {
138 StringRefCheckerVisitor walker(D, BR, Checker);
139 walker.Visit(S: D->getBody());
140}
141
142void StringRefCheckerVisitor::VisitDeclStmt(DeclStmt *S) {
143 VisitChildren(S);
144
145 for (auto *I : S->decls())
146 if (VarDecl *VD = dyn_cast<VarDecl>(Val: I))
147 VisitVarDecl(VD);
148}
149
150void StringRefCheckerVisitor::VisitVarDecl(VarDecl *VD) {
151 Expr *Init = VD->getInit();
152 if (!Init)
153 return;
154
155 // Pattern match for:
156 // StringRef x = call() (where call returns std::string)
157 if (!IsLLVMStringRef(T: VD->getType()))
158 return;
159 ExprWithCleanups *Ex1 = dyn_cast<ExprWithCleanups>(Val: Init);
160 if (!Ex1)
161 return;
162 CXXConstructExpr *Ex2 = dyn_cast<CXXConstructExpr>(Val: Ex1->getSubExpr());
163 if (!Ex2 || Ex2->getNumArgs() != 1)
164 return;
165 ImplicitCastExpr *Ex3 = dyn_cast<ImplicitCastExpr>(Val: Ex2->getArg(Arg: 0));
166 if (!Ex3)
167 return;
168 CXXConstructExpr *Ex4 = dyn_cast<CXXConstructExpr>(Val: Ex3->getSubExpr());
169 if (!Ex4 || Ex4->getNumArgs() != 1)
170 return;
171 ImplicitCastExpr *Ex5 = dyn_cast<ImplicitCastExpr>(Val: Ex4->getArg(Arg: 0));
172 if (!Ex5)
173 return;
174 CXXBindTemporaryExpr *Ex6 = dyn_cast<CXXBindTemporaryExpr>(Val: Ex5->getSubExpr());
175 if (!Ex6 || !IsStdString(T: Ex6->getType()))
176 return;
177
178 // Okay, badness! Report an error.
179 const char *desc = "StringRef should not be bound to temporary "
180 "std::string that it outlives";
181 PathDiagnosticLocation VDLoc =
182 PathDiagnosticLocation::createBegin(D: VD, SM: BR.getSourceManager());
183 BR.EmitBasicReport(DeclWithIssue, Checker, BugName: desc, BugCategory: "LLVM Conventions", BugStr: desc,
184 Loc: VDLoc, Ranges: Init->getSourceRange());
185}
186
187//===----------------------------------------------------------------------===//
188// CHECK: Clang AST nodes should not have fields that can allocate
189// memory.
190//===----------------------------------------------------------------------===//
191
192static bool AllocatesMemory(QualType T) {
193 return IsStdVector(T) || IsStdString(T) || IsSmallVector(T);
194}
195
196// This type checking could be sped up via dynamic programming.
197static bool IsPartOfAST(const CXXRecordDecl *R) {
198 if (IsClangStmt(RD: R) || IsClangType(RD: R) || IsClangDecl(RD: R) || IsClangAttr(RD: R))
199 return true;
200
201 for (const auto &BS : R->bases()) {
202 QualType T = BS.getType();
203 if (const RecordType *baseT = T->getAs<RecordType>()) {
204 CXXRecordDecl *baseD = cast<CXXRecordDecl>(Val: baseT->getDecl());
205 if (IsPartOfAST(R: baseD))
206 return true;
207 }
208 }
209
210 return false;
211}
212
213namespace {
214class ASTFieldVisitor {
215 SmallVector<FieldDecl*, 10> FieldChain;
216 const CXXRecordDecl *Root;
217 BugReporter &BR;
218 const CheckerBase *Checker;
219
220public:
221 ASTFieldVisitor(const CXXRecordDecl *root, BugReporter &br,
222 const CheckerBase *checker)
223 : Root(root), BR(br), Checker(checker) {}
224
225 void Visit(FieldDecl *D);
226 void ReportError(QualType T);
227};
228} // end anonymous namespace
229
230static void CheckASTMemory(const CXXRecordDecl *R, BugReporter &BR,
231 const CheckerBase *Checker) {
232 if (!IsPartOfAST(R))
233 return;
234
235 for (auto *I : R->fields()) {
236 ASTFieldVisitor walker(R, BR, Checker);
237 walker.Visit(D: I);
238 }
239}
240
241void ASTFieldVisitor::Visit(FieldDecl *D) {
242 FieldChain.push_back(Elt: D);
243
244 QualType T = D->getType();
245
246 if (AllocatesMemory(T))
247 ReportError(T);
248
249 if (const RecordType *RT = T->getAs<RecordType>()) {
250 const RecordDecl *RD = RT->getDecl()->getDefinition();
251 for (auto *I : RD->fields())
252 Visit(D: I);
253 }
254
255 FieldChain.pop_back();
256}
257
258void ASTFieldVisitor::ReportError(QualType T) {
259 SmallString<1024> buf;
260 llvm::raw_svector_ostream os(buf);
261
262 os << "AST class '" << Root->getName() << "' has a field '"
263 << FieldChain.front()->getName() << "' that allocates heap memory";
264 if (FieldChain.size() > 1) {
265 os << " via the following chain: ";
266 bool isFirst = true;
267 for (SmallVectorImpl<FieldDecl*>::iterator I=FieldChain.begin(),
268 E=FieldChain.end(); I!=E; ++I) {
269 if (!isFirst)
270 os << '.';
271 else
272 isFirst = false;
273 os << (*I)->getName();
274 }
275 }
276 os << " (type " << FieldChain.back()->getType() << ")";
277
278 // Note that this will fire for every translation unit that uses this
279 // class. This is suboptimal, but at least scan-build will merge
280 // duplicate HTML reports. In the future we need a unified way of merging
281 // duplicate reports across translation units. For C++ classes we cannot
282 // just report warnings when we see an out-of-line method definition for a
283 // class, as that heuristic doesn't always work (the complete definition of
284 // the class may be in the header file, for example).
285 PathDiagnosticLocation L = PathDiagnosticLocation::createBegin(
286 D: FieldChain.front(), SM: BR.getSourceManager());
287 BR.EmitBasicReport(DeclWithIssue: Root, Checker, BugName: "AST node allocates heap memory",
288 BugCategory: "LLVM Conventions", BugStr: os.str(), Loc: L);
289}
290
291//===----------------------------------------------------------------------===//
292// LLVMConventionsChecker
293//===----------------------------------------------------------------------===//
294
295namespace {
296class LLVMConventionsChecker : public Checker<
297 check::ASTDecl<CXXRecordDecl>,
298 check::ASTCodeBody > {
299public:
300 void checkASTDecl(const CXXRecordDecl *R, AnalysisManager& mgr,
301 BugReporter &BR) const {
302 if (R->isCompleteDefinition())
303 CheckASTMemory(R, BR, Checker: this);
304 }
305
306 void checkASTCodeBody(const Decl *D, AnalysisManager& mgr,
307 BugReporter &BR) const {
308 CheckStringRefAssignedTemporary(D, BR, Checker: this);
309 }
310};
311}
312
313void ento::registerLLVMConventionsChecker(CheckerManager &mgr) {
314 mgr.registerChecker<LLVMConventionsChecker>();
315}
316
317bool ento::shouldRegisterLLVMConventionsChecker(const CheckerManager &mgr) {
318 return true;
319}
320