build/clang-plugin/NaNExprChecker.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 "NaNExprChecker.h"
   6 #include "CustomMatchers.h"
   7
   8 void NaNExprChecker::registerMatchers(MatchFinder *AstMatcher) {
   9   AstMatcher->addMatcher(
  10       binaryOperator(
  11           allOf(binaryEqualityOperator(),
  12                 hasLHS(has(ignoringParenImpCasts(
  13                     declRefExpr(hasType(qualType((isFloat())))).bind("lhs")))),
  14                 hasRHS(has(ignoringParenImpCasts(
  15                     declRefExpr(hasType(qualType((isFloat())))).bind("rhs")))),
  16                 unless(anyOf(isInSystemHeader(), isInWhitelistForNaNExpr()))))
  17           .bind("node"),
  18       this);
  19 }
  20
  21 void NaNExprChecker::check(const MatchFinder::MatchResult &Result) {
  22   if (!Result.Context->getLangOpts().CPlusPlus) {
  23     return;
  24   }
  25
  26   const BinaryOperator *Expression =
  27       Result.Nodes.getNodeAs<BinaryOperator>("node");
  28   const DeclRefExpr *LHS = Result.Nodes.getNodeAs<DeclRefExpr>("lhs");
  29   const DeclRefExpr *RHS = Result.Nodes.getNodeAs<DeclRefExpr>("rhs");
  30   const ImplicitCastExpr *LHSExpr =
  31       dyn_cast<ImplicitCastExpr>(Expression->getLHS());
  32   const ImplicitCastExpr *RHSExpr =
  33       dyn_cast<ImplicitCastExpr>(Expression->getRHS());
  34   // The AST subtree that we are looking for will look like this:
  35   // -BinaryOperator ==/!=
  36   //  |-ImplicitCastExpr LValueToRValue
  37   //  | |-DeclRefExpr
  38   //  |-ImplicitCastExpr LValueToRValue
  39   //    |-DeclRefExpr
  40   // The check below ensures that we are dealing with the correct AST subtree
  41   // shape, and
  42   // also that both of the found DeclRefExpr's point to the same declaration.
  43   if (LHS->getFoundDecl() == RHS->getFoundDecl() && LHSExpr && RHSExpr &&
  44       std::distance(LHSExpr->child_begin(), LHSExpr->child_end()) == 1 &&
  45       std::distance(RHSExpr->child_begin(), RHSExpr->child_end()) == 1 &&
  46       *LHSExpr->child_begin() == LHS && *RHSExpr->child_begin() == RHS) {
  47     diag(Expression->getBeginLoc(),
  48          "comparing a floating point value to itself for "
  49          "NaN checking can lead to incorrect results",
  50          DiagnosticIDs::Error);
  51     diag(Expression->getBeginLoc(), "consider using std::isnan instead",
  52          DiagnosticIDs::Note);
  53   }
  54 }