build/clang-plugin/DanglingOnTemporaryChecker.cpp

   1 /* This Source Code Form is subject to the terms of the Mozilla Public
   2  * License, v. 2.0. If a copy of the MPL was not distributed with this
   3  * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
   4
   5 #include "DanglingOnTemporaryChecker.h"
   6 #include "CustomMatchers.h"
   7 #include "VariableUsageHelpers.h"
   8
   9 void DanglingOnTemporaryChecker::registerMatchers(MatchFinder *AstMatcher) {
  10   ////////////////////////////////////////
  11   // Quick annotation conflict checkers //
  12   ////////////////////////////////////////
  13
  14   AstMatcher->addMatcher(
  15       // This is a matcher on a method declaration,
  16       cxxMethodDecl(
  17           // which is marked as no dangling on temporaries,
  18           noDanglingOnTemporaries(),
  19
  20           // and which is && ref-qualified.
  21           isRValueRefQualified(),
  22
  23           decl().bind("invalidMethodRefQualified")),
  24       this);
  25
  26   AstMatcher->addMatcher(
  27       // This is a matcher on a method declaration,
  28       cxxMethodDecl(
  29           // which is marked as no dangling on temporaries,
  30           noDanglingOnTemporaries(),
  31
  32           // which returns a primitive type,
  33           returns(builtinType()),
  34
  35           // and which doesn't return a pointer.
  36           unless(returns(pointerType())),
  37
  38           decl().bind("invalidMethodPointer")),
  39       this);
  40
  41   //////////////////
  42   // Main checker //
  43   //////////////////
  44
  45   auto hasParentCall = hasParent(
  46       expr(anyOf(cxxOperatorCallExpr(
  47                      // If we're in a lamda, we may have an operator call
  48                      // expression ancestor in the AST, but the temporary we're
  49                      // matching against is not going to have the same lifetime
  50                      // as the constructor call.
  51                      unless(has(expr(ignoreTrivials(lambdaExpr())))),
  52                      expr().bind("parentOperatorCallExpr")),
  53                  callExpr(
  54                      // If we're in a lamda, we may have a call expression
  55                      // ancestor in the AST, but the temporary we're matching
  56                      // against is not going to have the same lifetime as the
  57                      // function call.
  58                      unless(has(expr(ignoreTrivials(lambdaExpr())))),
  59                      expr().bind("parentCallExpr")),
  60                  objcMessageExpr(
  61                      // If we're in a lamda, we may have an objc message
  62                      // expression ancestor in the AST, but the temporary we're
  63                      // matching against is not going to have the same lifetime
  64                      // as the function call.
  65                      unless(has(expr(ignoreTrivials(lambdaExpr())))),
  66                      expr().bind("parentObjCMessageExpr")),
  67                  cxxConstructExpr(
  68                      // If we're in a lamda, we may have a construct expression
  69                      // ancestor in the AST, but the temporary we're matching
  70                      // against is not going to have the same lifetime as the
  71                      // constructor call.
  72                      unless(has(expr(ignoreTrivials(lambdaExpr())))),
  73                      expr().bind("parentConstructExpr")))));
  74
  75   AstMatcher->addMatcher(
  76       // This is a matcher on a method call,
  77       cxxMemberCallExpr(
  78           // which is in first party code,
  79           isFirstParty(),
  80
  81           // and which is performed on a temporary,
  82           on(allOf(unless(hasType(pointerType())), isTemporary(),
  83                    // but which is not `this`.
  84                    unless(cxxThisExpr()))),
  85
  86           // and which is marked as no dangling on temporaries.
  87           callee(cxxMethodDecl(noDanglingOnTemporaries())),
  88
  89           expr().bind("memberCallExpr"),
  90
  91           // We optionally match a parent call expression or a parent construct
  92           // expression because using a temporary inside a call is fine as long
  93           // as the pointer doesn't escape the function call.
  94           anyOf(
  95               // This is the case where the call is the direct parent, so we
  96               // know that the member call expression is the argument.
  97               allOf(hasParentCall, expr().bind("parentCallArg")),
  98
  99               // This is the case where the call is not the direct parent, so we
 100               // get its child to know in which argument tree we are.
 101               hasAncestor(expr(hasParentCall, expr().bind("parentCallArg"))),
 102               // To make it optional.
 103               anything())),
 104       this);
 105 }
 106
 107 void DanglingOnTemporaryChecker::check(const MatchFinder::MatchResult &Result) {
 108   ///////////////////////////////////////
 109   // Quick annotation conflict checker //
 110   ///////////////////////////////////////
 111
 112   const char *ErrorInvalidRefQualified = "methods annotated with "
 113                                          "MOZ_NO_DANGLING_ON_TEMPORARIES "
 114                                          "cannot be && ref-qualified";
 115
 116   const char *ErrorInvalidPointer = "methods annotated with "
 117                                     "MOZ_NO_DANGLING_ON_TEMPORARIES must "
 118                                     "return a pointer";
 119
 120   if (auto InvalidRefQualified =
 121           Result.Nodes.getNodeAs<CXXMethodDecl>("invalidMethodRefQualified")) {
 122     diag(InvalidRefQualified->getLocation(), ErrorInvalidRefQualified,
 123          DiagnosticIDs::Error);
 124     return;
 125   }
 126
 127   if (auto InvalidPointer =
 128           Result.Nodes.getNodeAs<CXXMethodDecl>("invalidMethodPointer")) {
 129     diag(InvalidPointer->getLocation(), ErrorInvalidPointer,
 130          DiagnosticIDs::Error);
 131     return;
 132   }
 133
 134   //////////////////
 135   // Main checker //
 136   //////////////////
 137
 138   const char *Error = "calling `%0` on a temporary, potentially allowing use "
 139                       "after free of the raw pointer";
 140
 141   const char *EscapeStmtNote =
 142       "the raw pointer escapes the function scope here";
 143
 144   const ObjCMessageExpr *ParentObjCMessageExpr =
 145       Result.Nodes.getNodeAs<ObjCMessageExpr>("parentObjCMessageExpr");
 146
 147   // We don't care about cases in ObjC message expressions.
 148   if (ParentObjCMessageExpr) {
 149     return;
 150   }
 151
 152   const CXXMemberCallExpr *MemberCall =
 153       Result.Nodes.getNodeAs<CXXMemberCallExpr>("memberCallExpr");
 154
 155   const CallExpr *ParentCallExpr =
 156       Result.Nodes.getNodeAs<CallExpr>("parentCallExpr");
 157   const CXXConstructExpr *ParentConstructExpr =
 158       Result.Nodes.getNodeAs<CXXConstructExpr>("parentConstructExpr");
 159   const CXXOperatorCallExpr *ParentOperatorCallExpr =
 160       Result.Nodes.getNodeAs<CXXOperatorCallExpr>("parentOperatorCallExpr");
 161   const Expr *ParentCallArg = Result.Nodes.getNodeAs<Expr>("parentCallArg");
 162
 163   // Just in case.
 164   if (!MemberCall) {
 165     return;
 166   }
 167
 168   // If we have a parent call, we check whether or not we escape the function
 169   // being called.
 170   if (ParentOperatorCallExpr || ParentCallExpr || ParentConstructExpr) {
 171     // Just in case.
 172     if (!ParentCallArg) {
 173       return;
 174     }
 175
 176     // No default constructor so we can't construct it using if/else.
 177     auto FunctionEscapeData =
 178         ParentOperatorCallExpr
 179             ? escapesFunction(ParentCallArg, ParentOperatorCallExpr)
 180             : ParentCallExpr
 181                   ? escapesFunction(ParentCallArg, ParentCallExpr)
 182                   : escapesFunction(ParentCallArg, ParentConstructExpr);
 183
 184     // If there was an error in the escapesFunction call.
 185     if (std::error_code ec = FunctionEscapeData.getError()) {
 186       // FIXME: For now we ignore the variadic case and just consider that the
 187       // argument doesn't escape the function. Same for the case where we can't
 188       // find the function declaration or if the function is builtin.
 189       if (static_cast<EscapesFunctionError>(ec.value()) ==
 190               EscapesFunctionError::FunctionIsVariadic ||
 191           static_cast<EscapesFunctionError>(ec.value()) ==
 192               EscapesFunctionError::FunctionDeclNotFound ||
 193           static_cast<EscapesFunctionError>(ec.value()) ==
 194               EscapesFunctionError::FunctionIsBuiltin) {
 195         return;
 196       }
 197
 198       // We emit the internal checker error and return.
 199       diag(MemberCall->getExprLoc(),
 200            std::string(ec.category().name()) + " error: " + ec.message(),
 201            DiagnosticIDs::Error);
 202       return;
 203     }
 204
 205     // We deconstruct the function escape data.
 206     const Stmt *EscapeStmt;
 207     const Decl *EscapeDecl;
 208     std::tie(EscapeStmt, EscapeDecl) = *FunctionEscapeData;
 209
 210     // If we didn't escape a parent function, we're done: we don't emit any
 211     // diagnostic.
 212     if (!EscapeStmt || !EscapeDecl) {
 213       return;
 214     }
 215
 216     // We emit the error diagnostic indicating that we are calling the method
 217     // temporary.
 218     diag(MemberCall->getExprLoc(), Error, DiagnosticIDs::Error)
 219         << MemberCall->getMethodDecl()->getName()
 220         << MemberCall->getSourceRange();
 221
 222     // We indicate the escape statement.
 223     diag(EscapeStmt->getBeginLoc(), EscapeStmtNote, DiagnosticIDs::Note)
 224         << EscapeStmt->getSourceRange();
 225
 226     // We build the escape note along with its source range.
 227     StringRef EscapeDeclNote;
 228     SourceRange EscapeDeclRange;
 229     if (isa<ParmVarDecl>(EscapeDecl)) {
 230       EscapeDeclNote = "through the parameter declared here";
 231       EscapeDeclRange = EscapeDecl->getSourceRange();
 232     } else if (isa<VarDecl>(EscapeDecl)) {
 233       EscapeDeclNote = "through the variable declared here";
 234       EscapeDeclRange = EscapeDecl->getSourceRange();
 235     } else if (isa<FieldDecl>(EscapeDecl)) {
 236       EscapeDeclNote = "through the field declared here";
 237       EscapeDeclRange = EscapeDecl->getSourceRange();
 238     } else if (auto FuncDecl = dyn_cast<FunctionDecl>(EscapeDecl)) {
 239       EscapeDeclNote = "through the return value of the function declared here";
 240       EscapeDeclRange = FuncDecl->getReturnTypeSourceRange();
 241     } else {
 242       return;
 243     }
 244
 245     // We emit the declaration note indicating through which decl the argument
 246     // escapes.
 247     diag(EscapeDecl->getLocation(), EscapeDeclNote, DiagnosticIDs::Note)
 248         << EscapeDeclRange;
 249   } else {
 250     // We emit the error diagnostic indicating that we are calling the method
 251     // temporary.
 252     diag(MemberCall->getExprLoc(), Error, DiagnosticIDs::Error)
 253         << MemberCall->getMethodDecl()->getName()
 254         << MemberCall->getSourceRange();
 255   }
 256 }