lib/Checker/LLVMConventionsChecker.cpp

   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 "clang/AST/DeclTemplate.h"
  16 #include "clang/AST/StmtVisitor.h"
  17 #include "clang/GR/Checkers/LocalCheckers.h"
  18 #include "clang/GR/BugReporter/BugReporter.h"
  19 #include <string>
  20 #include "llvm/ADT/StringRef.h"
  21
  22 using namespace clang;
  23
  24 //===----------------------------------------------------------------------===//
  25 // Generic type checking routines.
  26 //===----------------------------------------------------------------------===//
  27
  28 static bool IsLLVMStringRef(QualType T) {
  29   const RecordType *RT = T->getAs<RecordType>();
  30   if (!RT)
  31     return false;
  32
  33   return llvm::StringRef(QualType(RT, 0).getAsString()) ==
  34           "class llvm::StringRef";
  35 }
  36
  37 /// Check whether the declaration is semantically inside the top-level
  38 /// namespace named by ns.
  39 static bool InNamespace(const Decl *D, llvm::StringRef NS) {
  40   const DeclContext *DC = D->getDeclContext();
  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   DC = ND->getDeclContext();
  48   return isa<TranslationUnitDecl>(DC);
  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 TypedefDecl *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 llvm::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   // llvm::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
 179   BR.EmitBasicReport(desc, "LLVM Conventions", desc,
 180                      VD->getLocStart(), 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   llvm::SmallVector<FieldDecl*, 10> FieldChain;
 214   CXXRecordDecl *Root;
 215   BugReporter &BR;
 216 public:
 217   ASTFieldVisitor(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(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 (llvm::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   BR.EmitBasicReport("AST node allocates heap memory", "LLVM Conventions",
 283                      os.str(), FieldChain.front()->getLocStart());
 284 }
 285
 286 //===----------------------------------------------------------------------===//
 287 // Entry point for all checks.
 288 //===----------------------------------------------------------------------===//
 289
 290 static void ScanCodeDecls(DeclContext *DC, BugReporter &BR) {
 291   for (DeclContext::decl_iterator I=DC->decls_begin(), E=DC->decls_end();
 292        I!=E ; ++I) {
 293
 294     Decl *D = *I;
 295
 296     if (D->hasBody())
 297       CheckStringRefAssignedTemporary(D, BR);
 298
 299     if (CXXRecordDecl *R = dyn_cast<CXXRecordDecl>(D))
 300       if (R->isDefinition())
 301         CheckASTMemory(R, BR);
 302
 303     if (DeclContext *DC_child = dyn_cast<DeclContext>(D))
 304       ScanCodeDecls(DC_child, BR);
 305   }
 306 }
 307
 308 void clang::CheckLLVMConventions(TranslationUnitDecl &TU,
 309                                  BugReporter &BR) {
 310   ScanCodeDecls(&TU, BR);
 311 }
 312