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