1 //=== LLVMConventionsChecker.cpp - Check LLVM codebase conventions ---*- C++ -*- 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 defines LLVMConventionsChecker, a bunch of small little checks 11 // for checking specific coding conventions in the LLVM/Clang codebase. 12 // 13 //===----------------------------------------------------------------------===// 14 15 #include "ClangSACheckers.h" 16 #include "clang/AST/DeclTemplate.h" 17 #include "clang/AST/StmtVisitor.h" 18 #include "clang/StaticAnalyzer/Core/BugReporter/BugReporter.h" 19 #include "clang/StaticAnalyzer/Core/Checker.h" 20 #include "llvm/ADT/SmallString.h" 21 #include "llvm/Support/raw_ostream.h" 22 23 using namespace clang; 24 using namespace ento; 25 26 //===----------------------------------------------------------------------===// 27 // Generic type checking routines. 28 //===----------------------------------------------------------------------===// 29 30 static bool IsLLVMStringRef(QualType T) { 31 const RecordType *RT = T->getAs<RecordType>(); 32 if (!RT) 33 return false; 34 35 return StringRef(QualType(RT, 0).getAsString()) == 36 "class StringRef"; 37 } 38 39 /// Check whether the declaration is semantically inside the top-level 40 /// namespace named by ns. 41 static bool InNamespace(const Decl *D, StringRef NS) { 42 const NamespaceDecl *ND = dyn_cast<NamespaceDecl>(D->getDeclContext()); 43 if (!ND) 44 return false; 45 const IdentifierInfo *II = ND->getIdentifier(); 46 if (!II || !II->getName().equals(NS)) 47 return false; 48 return isa<TranslationUnitDecl>(ND->getDeclContext()); 49 } 50 51 static bool IsStdString(QualType T) { 52 if (const ElaboratedType *QT = T->getAs<ElaboratedType>()) 53 T = QT->getNamedType(); 54 55 const TypedefType *TT = T->getAs<TypedefType>(); 56 if (!TT) 57 return false; 58 59 const TypedefNameDecl *TD = TT->getDecl(); 60 61 if (!InNamespace(TD, "std")) 62 return false; 63 64 return TD->getName() == "string"; 65 } 66 67 static bool IsClangType(const RecordDecl *RD) { 68 return RD->getName() == "Type" && InNamespace(RD, "clang"); 69 } 70 71 static bool IsClangDecl(const RecordDecl *RD) { 72 return RD->getName() == "Decl" && InNamespace(RD, "clang"); 73 } 74 75 static bool IsClangStmt(const RecordDecl *RD) { 76 return RD->getName() == "Stmt" && InNamespace(RD, "clang"); 77 } 78 79 static bool IsClangAttr(const RecordDecl *RD) { 80 return RD->getName() == "Attr" && InNamespace(RD, "clang"); 81 } 82 83 static bool IsStdVector(QualType T) { 84 const TemplateSpecializationType *TS = T->getAs<TemplateSpecializationType>(); 85 if (!TS) 86 return false; 87 88 TemplateName TM = TS->getTemplateName(); 89 TemplateDecl *TD = TM.getAsTemplateDecl(); 90 91 if (!TD || !InNamespace(TD, "std")) 92 return false; 93 94 return TD->getName() == "vector"; 95 } 96 97 static bool IsSmallVector(QualType T) { 98 const TemplateSpecializationType *TS = T->getAs<TemplateSpecializationType>(); 99 if (!TS) 100 return false; 101 102 TemplateName TM = TS->getTemplateName(); 103 TemplateDecl *TD = TM.getAsTemplateDecl(); 104 105 if (!TD || !InNamespace(TD, "llvm")) 106 return false; 107 108 return TD->getName() == "SmallVector"; 109 } 110 111 //===----------------------------------------------------------------------===// 112 // CHECK: a StringRef should not be bound to a temporary std::string whose 113 // lifetime is shorter than the StringRef's. 114 //===----------------------------------------------------------------------===// 115 116 namespace { 117 class StringRefCheckerVisitor : public StmtVisitor<StringRefCheckerVisitor> { 118 const Decl *DeclWithIssue; 119 BugReporter &BR; 120 const CheckerBase *Checker; 121 122 public: 123 StringRefCheckerVisitor(const Decl *declWithIssue, BugReporter &br, 124 const CheckerBase *checker) 125 : DeclWithIssue(declWithIssue), BR(br), Checker(checker) {} 126 void VisitChildren(Stmt *S) { 127 for (Stmt::child_iterator I = S->child_begin(), E = S->child_end() ; 128 I != E; ++I) 129 if (Stmt *child = *I) 130 Visit(child); 131 } 132 void VisitStmt(Stmt *S) { VisitChildren(S); } 133 void VisitDeclStmt(DeclStmt *DS); 134 private: 135 void VisitVarDecl(VarDecl *VD); 136 }; 137 } // end anonymous namespace 138 139 static void CheckStringRefAssignedTemporary(const Decl *D, BugReporter &BR, 140 const CheckerBase *Checker) { 141 StringRefCheckerVisitor walker(D, BR, Checker); 142 walker.Visit(D->getBody()); 143 } 144 145 void StringRefCheckerVisitor::VisitDeclStmt(DeclStmt *S) { 146 VisitChildren(S); 147 148 for (DeclStmt::decl_iterator I = S->decl_begin(), E = S->decl_end();I!=E; ++I) 149 if (VarDecl *VD = dyn_cast<VarDecl>(*I)) 150 VisitVarDecl(VD); 151 } 152 153 void StringRefCheckerVisitor::VisitVarDecl(VarDecl *VD) { 154 Expr *Init = VD->getInit(); 155 if (!Init) 156 return; 157 158 // Pattern match for: 159 // StringRef x = call() (where call returns std::string) 160 if (!IsLLVMStringRef(VD->getType())) 161 return; 162 ExprWithCleanups *Ex1 = dyn_cast<ExprWithCleanups>(Init); 163 if (!Ex1) 164 return; 165 CXXConstructExpr *Ex2 = dyn_cast<CXXConstructExpr>(Ex1->getSubExpr()); 166 if (!Ex2 || Ex2->getNumArgs() != 1) 167 return; 168 ImplicitCastExpr *Ex3 = dyn_cast<ImplicitCastExpr>(Ex2->getArg(0)); 169 if (!Ex3) 170 return; 171 CXXConstructExpr *Ex4 = dyn_cast<CXXConstructExpr>(Ex3->getSubExpr()); 172 if (!Ex4 || Ex4->getNumArgs() != 1) 173 return; 174 ImplicitCastExpr *Ex5 = dyn_cast<ImplicitCastExpr>(Ex4->getArg(0)); 175 if (!Ex5) 176 return; 177 CXXBindTemporaryExpr *Ex6 = dyn_cast<CXXBindTemporaryExpr>(Ex5->getSubExpr()); 178 if (!Ex6 || !IsStdString(Ex6->getType())) 179 return; 180 181 // Okay, badness! Report an error. 182 const char *desc = "StringRef should not be bound to temporary " 183 "std::string that it outlives"; 184 PathDiagnosticLocation VDLoc = 185 PathDiagnosticLocation::createBegin(VD, BR.getSourceManager()); 186 BR.EmitBasicReport(DeclWithIssue, Checker, desc, "LLVM Conventions", desc, 187 VDLoc, Init->getSourceRange()); 188 } 189 190 //===----------------------------------------------------------------------===// 191 // CHECK: Clang AST nodes should not have fields that can allocate 192 // memory. 193 //===----------------------------------------------------------------------===// 194 195 static bool AllocatesMemory(QualType T) { 196 return IsStdVector(T) || IsStdString(T) || IsSmallVector(T); 197 } 198 199 // This type checking could be sped up via dynamic programming. 200 static bool IsPartOfAST(const CXXRecordDecl *R) { 201 if (IsClangStmt(R) || IsClangType(R) || IsClangDecl(R) || IsClangAttr(R)) 202 return true; 203 204 for (CXXRecordDecl::base_class_const_iterator I = R->bases_begin(), 205 E = R->bases_end(); I!=E; ++I) { 206 CXXBaseSpecifier BS = *I; 207 QualType T = BS.getType(); 208 if (const RecordType *baseT = T->getAs<RecordType>()) { 209 CXXRecordDecl *baseD = cast<CXXRecordDecl>(baseT->getDecl()); 210 if (IsPartOfAST(baseD)) 211 return true; 212 } 213 } 214 215 return false; 216 } 217 218 namespace { 219 class ASTFieldVisitor { 220 SmallVector<FieldDecl*, 10> FieldChain; 221 const CXXRecordDecl *Root; 222 BugReporter &BR; 223 const CheckerBase *Checker; 224 225 public: 226 ASTFieldVisitor(const CXXRecordDecl *root, BugReporter &br, 227 const CheckerBase *checker) 228 : Root(root), BR(br), Checker(checker) {} 229 230 void Visit(FieldDecl *D); 231 void ReportError(QualType T); 232 }; 233 } // end anonymous namespace 234 235 static void CheckASTMemory(const CXXRecordDecl *R, BugReporter &BR, 236 const CheckerBase *Checker) { 237 if (!IsPartOfAST(R)) 238 return; 239 240 for (auto *I : R->fields()) { 241 ASTFieldVisitor walker(R, BR, Checker); 242 walker.Visit(I); 243 } 244 } 245 246 void ASTFieldVisitor::Visit(FieldDecl *D) { 247 FieldChain.push_back(D); 248 249 QualType T = D->getType(); 250 251 if (AllocatesMemory(T)) 252 ReportError(T); 253 254 if (const RecordType *RT = T->getAs<RecordType>()) { 255 const RecordDecl *RD = RT->getDecl()->getDefinition(); 256 for (auto *I : RD->fields()) 257 Visit(I); 258 } 259 260 FieldChain.pop_back(); 261 } 262 263 void ASTFieldVisitor::ReportError(QualType T) { 264 SmallString<1024> buf; 265 llvm::raw_svector_ostream os(buf); 266 267 os << "AST class '" << Root->getName() << "' has a field '" 268 << FieldChain.front()->getName() << "' that allocates heap memory"; 269 if (FieldChain.size() > 1) { 270 os << " via the following chain: "; 271 bool isFirst = true; 272 for (SmallVectorImpl<FieldDecl*>::iterator I=FieldChain.begin(), 273 E=FieldChain.end(); I!=E; ++I) { 274 if (!isFirst) 275 os << '.'; 276 else 277 isFirst = false; 278 os << (*I)->getName(); 279 } 280 } 281 os << " (type " << FieldChain.back()->getType().getAsString() << ")"; 282 os.flush(); 283 284 // Note that this will fire for every translation unit that uses this 285 // class. This is suboptimal, but at least scan-build will merge 286 // duplicate HTML reports. In the future we need a unified way of merging 287 // duplicate reports across translation units. For C++ classes we cannot 288 // just report warnings when we see an out-of-line method definition for a 289 // class, as that heuristic doesn't always work (the complete definition of 290 // the class may be in the header file, for example). 291 PathDiagnosticLocation L = PathDiagnosticLocation::createBegin( 292 FieldChain.front(), BR.getSourceManager()); 293 BR.EmitBasicReport(Root, Checker, "AST node allocates heap memory", 294 "LLVM Conventions", os.str(), L); 295 } 296 297 //===----------------------------------------------------------------------===// 298 // LLVMConventionsChecker 299 //===----------------------------------------------------------------------===// 300 301 namespace { 302 class LLVMConventionsChecker : public Checker< 303 check::ASTDecl<CXXRecordDecl>, 304 check::ASTCodeBody > { 305 public: 306 void checkASTDecl(const CXXRecordDecl *R, AnalysisManager& mgr, 307 BugReporter &BR) const { 308 if (R->isCompleteDefinition()) 309 CheckASTMemory(R, BR, this); 310 } 311 312 void checkASTCodeBody(const Decl *D, AnalysisManager& mgr, 313 BugReporter &BR) const { 314 CheckStringRefAssignedTemporary(D, BR, this); 315 } 316 }; 317 } 318 319 void ento::registerLLVMConventionsChecker(CheckerManager &mgr) { 320 mgr.registerChecker<LLVMConventionsChecker>(); 321 } 322