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 <string> 21 #include "llvm/ADT/StringRef.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 BugReporter &BR; 119 public: 120 StringRefCheckerVisitor(BugReporter &br) : BR(br) {} 121 void VisitChildren(Stmt *S) { 122 for (Stmt::child_iterator I = S->child_begin(), E = S->child_end() ; 123 I != E; ++I) 124 if (Stmt *child = *I) 125 Visit(child); 126 } 127 void VisitStmt(Stmt *S) { VisitChildren(S); } 128 void VisitDeclStmt(DeclStmt *DS); 129 private: 130 void VisitVarDecl(VarDecl *VD); 131 }; 132 } // end anonymous namespace 133 134 static void CheckStringRefAssignedTemporary(const Decl *D, BugReporter &BR) { 135 StringRefCheckerVisitor walker(BR); 136 walker.Visit(D->getBody()); 137 } 138 139 void StringRefCheckerVisitor::VisitDeclStmt(DeclStmt *S) { 140 VisitChildren(S); 141 142 for (DeclStmt::decl_iterator I = S->decl_begin(), E = S->decl_end();I!=E; ++I) 143 if (VarDecl *VD = dyn_cast<VarDecl>(*I)) 144 VisitVarDecl(VD); 145 } 146 147 void StringRefCheckerVisitor::VisitVarDecl(VarDecl *VD) { 148 Expr *Init = VD->getInit(); 149 if (!Init) 150 return; 151 152 // Pattern match for: 153 // StringRef x = call() (where call returns std::string) 154 if (!IsLLVMStringRef(VD->getType())) 155 return; 156 ExprWithCleanups *Ex1 = dyn_cast<ExprWithCleanups>(Init); 157 if (!Ex1) 158 return; 159 CXXConstructExpr *Ex2 = dyn_cast<CXXConstructExpr>(Ex1->getSubExpr()); 160 if (!Ex2 || Ex2->getNumArgs() != 1) 161 return; 162 ImplicitCastExpr *Ex3 = dyn_cast<ImplicitCastExpr>(Ex2->getArg(0)); 163 if (!Ex3) 164 return; 165 CXXConstructExpr *Ex4 = dyn_cast<CXXConstructExpr>(Ex3->getSubExpr()); 166 if (!Ex4 || Ex4->getNumArgs() != 1) 167 return; 168 ImplicitCastExpr *Ex5 = dyn_cast<ImplicitCastExpr>(Ex4->getArg(0)); 169 if (!Ex5) 170 return; 171 CXXBindTemporaryExpr *Ex6 = dyn_cast<CXXBindTemporaryExpr>(Ex5->getSubExpr()); 172 if (!Ex6 || !IsStdString(Ex6->getType())) 173 return; 174 175 // Okay, badness! Report an error. 176 const char *desc = "StringRef should not be bound to temporary " 177 "std::string that it outlives"; 178 PathDiagnosticLocation VDLoc = 179 PathDiagnosticLocation::createBegin(VD, BR.getSourceManager()); 180 BR.EmitBasicReport(desc, "LLVM Conventions", desc, 181 VDLoc, Init->getSourceRange()); 182 } 183 184 //===----------------------------------------------------------------------===// 185 // CHECK: Clang AST nodes should not have fields that can allocate 186 // memory. 187 //===----------------------------------------------------------------------===// 188 189 static bool AllocatesMemory(QualType T) { 190 return IsStdVector(T) || IsStdString(T) || IsSmallVector(T); 191 } 192 193 // This type checking could be sped up via dynamic programming. 194 static bool IsPartOfAST(const CXXRecordDecl *R) { 195 if (IsClangStmt(R) || IsClangType(R) || IsClangDecl(R) || IsClangAttr(R)) 196 return true; 197 198 for (CXXRecordDecl::base_class_const_iterator I = R->bases_begin(), 199 E = R->bases_end(); I!=E; ++I) { 200 CXXBaseSpecifier BS = *I; 201 QualType T = BS.getType(); 202 if (const RecordType *baseT = T->getAs<RecordType>()) { 203 CXXRecordDecl *baseD = cast<CXXRecordDecl>(baseT->getDecl()); 204 if (IsPartOfAST(baseD)) 205 return true; 206 } 207 } 208 209 return false; 210 } 211 212 namespace { 213 class ASTFieldVisitor { 214 SmallVector<FieldDecl*, 10> FieldChain; 215 const CXXRecordDecl *Root; 216 BugReporter &BR; 217 public: 218 ASTFieldVisitor(const CXXRecordDecl *root, BugReporter &br) 219 : Root(root), BR(br) {} 220 221 void Visit(FieldDecl *D); 222 void ReportError(QualType T); 223 }; 224 } // end anonymous namespace 225 226 static void CheckASTMemory(const CXXRecordDecl *R, BugReporter &BR) { 227 if (!IsPartOfAST(R)) 228 return; 229 230 for (RecordDecl::field_iterator I = R->field_begin(), E = R->field_end(); 231 I != E; ++I) { 232 ASTFieldVisitor walker(R, BR); 233 walker.Visit(*I); 234 } 235 } 236 237 void ASTFieldVisitor::Visit(FieldDecl *D) { 238 FieldChain.push_back(D); 239 240 QualType T = D->getType(); 241 242 if (AllocatesMemory(T)) 243 ReportError(T); 244 245 if (const RecordType *RT = T->getAs<RecordType>()) { 246 const RecordDecl *RD = RT->getDecl()->getDefinition(); 247 for (RecordDecl::field_iterator I = RD->field_begin(), E = RD->field_end(); 248 I != E; ++I) 249 Visit(*I); 250 } 251 252 FieldChain.pop_back(); 253 } 254 255 void ASTFieldVisitor::ReportError(QualType T) { 256 llvm::SmallString<1024> buf; 257 llvm::raw_svector_ostream os(buf); 258 259 os << "AST class '" << Root->getName() << "' has a field '" 260 << FieldChain.front()->getName() << "' that allocates heap memory"; 261 if (FieldChain.size() > 1) { 262 os << " via the following chain: "; 263 bool isFirst = true; 264 for (SmallVectorImpl<FieldDecl*>::iterator I=FieldChain.begin(), 265 E=FieldChain.end(); I!=E; ++I) { 266 if (!isFirst) 267 os << '.'; 268 else 269 isFirst = false; 270 os << (*I)->getName(); 271 } 272 } 273 os << " (type " << FieldChain.back()->getType().getAsString() << ")"; 274 os.flush(); 275 276 // Note that this will fire for every translation unit that uses this 277 // class. This is suboptimal, but at least scan-build will merge 278 // duplicate HTML reports. In the future we need a unified way of merging 279 // duplicate reports across translation units. For C++ classes we cannot 280 // just report warnings when we see an out-of-line method definition for a 281 // class, as that heuristic doesn't always work (the complete definition of 282 // the class may be in the header file, for example). 283 PathDiagnosticLocation L = PathDiagnosticLocation::createBegin( 284 FieldChain.front(), BR.getSourceManager()); 285 BR.EmitBasicReport("AST node allocates heap memory", "LLVM Conventions", 286 os.str(), L); 287 } 288 289 //===----------------------------------------------------------------------===// 290 // LLVMConventionsChecker 291 //===----------------------------------------------------------------------===// 292 293 namespace { 294 class LLVMConventionsChecker : public Checker< 295 check::ASTDecl<CXXRecordDecl>, 296 check::ASTCodeBody > { 297 public: 298 void checkASTDecl(const CXXRecordDecl *R, AnalysisManager& mgr, 299 BugReporter &BR) const { 300 if (R->isCompleteDefinition()) 301 CheckASTMemory(R, BR); 302 } 303 304 void checkASTCodeBody(const Decl *D, AnalysisManager& mgr, 305 BugReporter &BR) const { 306 CheckStringRefAssignedTemporary(D, BR); 307 } 308 }; 309 } 310 311 void ento::registerLLVMConventionsChecker(CheckerManager &mgr) { 312 mgr.registerChecker<LLVMConventionsChecker>(); 313 } 314