| //===--- MemsetZeroLengthCheck.cpp - clang-tidy -------------------*- C++ -*-===// |
| // |
| // The LLVM Compiler Infrastructure |
| // |
| // This file is distributed under the University of Illinois Open Source |
| // License. See LICENSE.TXT for details. |
| // |
| //===----------------------------------------------------------------------===// |
| |
| #include "MemsetZeroLengthCheck.h" |
| #include "clang/ASTMatchers/ASTMatchFinder.h" |
| #include "clang/ASTMatchers/ASTMatchers.h" |
| #include "clang/AST/ASTContext.h" |
| #include "clang/Lex/Lexer.h" |
| |
| using namespace clang::ast_matchers; |
| |
| namespace clang { |
| namespace tidy { |
| namespace runtime { |
| |
| void |
| MemsetZeroLengthCheck::registerMatchers(ast_matchers::MatchFinder *Finder) { |
| auto InTemplateInstantiation = hasAncestor( |
| decl(anyOf(recordDecl(ast_matchers::isTemplateInstantiation()), |
| functionDecl(ast_matchers::isTemplateInstantiation())))); |
| // Look for memset(x, y, 0) as those is most likely an argument swap. |
| // TODO: Also handle other standard functions that suffer from the same |
| // problem, e.g. memchr. |
| Finder->addMatcher( |
| callExpr(callee(functionDecl(hasName("::memset"))), argumentCountIs(3), |
| unless(InTemplateInstantiation)).bind("decl"), |
| this); |
| } |
| |
| /// \brief Get a StringRef representing a SourceRange. |
| static StringRef getAsString(const MatchFinder::MatchResult &Result, |
| SourceRange R) { |
| const SourceManager &SM = *Result.SourceManager; |
| // Don't even try to resolve macro or include contraptions. Not worth emitting |
| // a fixit for. |
| if (R.getBegin().isMacroID() || |
| !SM.isWrittenInSameFile(R.getBegin(), R.getEnd())) |
| return StringRef(); |
| |
| const char *Begin = SM.getCharacterData(R.getBegin()); |
| const char *End = SM.getCharacterData(Lexer::getLocForEndOfToken( |
| R.getEnd(), 0, SM, Result.Context->getLangOpts())); |
| |
| return StringRef(Begin, End - Begin); |
| } |
| |
| void MemsetZeroLengthCheck::check(const MatchFinder::MatchResult &Result) { |
| const auto *Call = Result.Nodes.getNodeAs<CallExpr>("decl"); |
| |
| const Expr *Arg1 = Call->getArg(1); |
| const Expr *Arg2 = Call->getArg(2); |
| |
| // Try to evaluate the second argument so we can also find values that are not |
| // just literals. |
| llvm::APSInt Value1, Value2; |
| if (Arg2->isValueDependent() || |
| !Arg2->EvaluateAsInt(Value2, *Result.Context) || Value2 != 0) |
| return; |
| |
| // If both arguments evaluate to zero emit a warning without fix suggestions. |
| if (!Arg1->isValueDependent() && |
| Arg1->EvaluateAsInt(Value1, *Result.Context) && |
| (Value1 == 0 || Value1.isNegative())) { |
| diag(Call->getLocStart(), "memset of size zero"); |
| return; |
| } |
| |
| // Emit a warning and fix-its to swap the arguments. |
| auto D = diag(Call->getLocStart(), |
| "memset of size zero, potentially swapped arguments"); |
| SourceRange LHSRange = Arg1->getSourceRange(); |
| SourceRange RHSRange = Arg2->getSourceRange(); |
| StringRef RHSString = getAsString(Result, RHSRange); |
| StringRef LHSString = getAsString(Result, LHSRange); |
| if (LHSString.empty() || RHSString.empty()) |
| return; |
| |
| D << FixItHint::CreateReplacement(CharSourceRange::getTokenRange(LHSRange), |
| RHSString) |
| << FixItHint::CreateReplacement(CharSourceRange::getTokenRange(RHSRange), |
| LHSString); |
| } |
| |
| } // namespace runtime |
| } // namespace tidy |
| } // namespace clang |