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to reflect the new license. We understand that people may be surprised that we're moving the header entirely to discuss the new license. We checked this carefully with the Foundation's lawyer and we believe this is the correct approach. Essentially, all code in the project is now made available by the LLVM project under our new license, so you will see that the license headers include that license only. Some of our contributors have contributed code under our old license, and accordingly, we have retained a copy of our old license notice in the top-level files in each project and repository. llvm-svn: 351636
117 lines
4.6 KiB
C++
117 lines
4.6 KiB
C++
//===--- ForRangeCopyCheck.cpp - clang-tidy--------------------------------===//
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//
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// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
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// See https://llvm.org/LICENSE.txt for license information.
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// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
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//
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//===----------------------------------------------------------------------===//
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#include "ForRangeCopyCheck.h"
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#include "../utils/DeclRefExprUtils.h"
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#include "../utils/FixItHintUtils.h"
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#include "../utils/Matchers.h"
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#include "../utils/OptionsUtils.h"
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#include "../utils/TypeTraits.h"
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#include "clang/Analysis/Analyses/ExprMutationAnalyzer.h"
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using namespace clang::ast_matchers;
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namespace clang {
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namespace tidy {
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namespace performance {
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ForRangeCopyCheck::ForRangeCopyCheck(StringRef Name, ClangTidyContext *Context)
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: ClangTidyCheck(Name, Context),
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WarnOnAllAutoCopies(Options.get("WarnOnAllAutoCopies", 0)),
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AllowedTypes(
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utils::options::parseStringList(Options.get("AllowedTypes", ""))) {}
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void ForRangeCopyCheck::storeOptions(ClangTidyOptions::OptionMap &Opts) {
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Options.store(Opts, "WarnOnAllAutoCopies", WarnOnAllAutoCopies);
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Options.store(Opts, "AllowedTypes",
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utils::options::serializeStringList(AllowedTypes));
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}
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void ForRangeCopyCheck::registerMatchers(MatchFinder *Finder) {
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// Match loop variables that are not references or pointers or are already
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// initialized through MaterializeTemporaryExpr which indicates a type
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// conversion.
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auto LoopVar = varDecl(
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hasType(qualType(
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unless(anyOf(hasCanonicalType(anyOf(referenceType(), pointerType())),
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hasDeclaration(namedDecl(
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matchers::matchesAnyListedName(AllowedTypes))))))),
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unless(hasInitializer(expr(hasDescendant(materializeTemporaryExpr())))));
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Finder->addMatcher(cxxForRangeStmt(hasLoopVariable(LoopVar.bind("loopVar")))
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.bind("forRange"),
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this);
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}
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void ForRangeCopyCheck::check(const MatchFinder::MatchResult &Result) {
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const auto *Var = Result.Nodes.getNodeAs<VarDecl>("loopVar");
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// Ignore code in macros since we can't place the fixes correctly.
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if (Var->getBeginLoc().isMacroID())
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return;
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if (handleConstValueCopy(*Var, *Result.Context))
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return;
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const auto *ForRange = Result.Nodes.getNodeAs<CXXForRangeStmt>("forRange");
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handleCopyIsOnlyConstReferenced(*Var, *ForRange, *Result.Context);
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}
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bool ForRangeCopyCheck::handleConstValueCopy(const VarDecl &LoopVar,
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ASTContext &Context) {
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if (WarnOnAllAutoCopies) {
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// For aggressive check just test that loop variable has auto type.
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if (!isa<AutoType>(LoopVar.getType()))
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return false;
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} else if (!LoopVar.getType().isConstQualified()) {
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return false;
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}
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llvm::Optional<bool> Expensive =
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utils::type_traits::isExpensiveToCopy(LoopVar.getType(), Context);
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if (!Expensive || !*Expensive)
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return false;
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auto Diagnostic =
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diag(LoopVar.getLocation(),
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"the loop variable's type is not a reference type; this creates a "
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"copy in each iteration; consider making this a reference")
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<< utils::fixit::changeVarDeclToReference(LoopVar, Context);
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if (!LoopVar.getType().isConstQualified())
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Diagnostic << utils::fixit::changeVarDeclToConst(LoopVar);
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return true;
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}
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bool ForRangeCopyCheck::handleCopyIsOnlyConstReferenced(
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const VarDecl &LoopVar, const CXXForRangeStmt &ForRange,
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ASTContext &Context) {
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llvm::Optional<bool> Expensive =
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utils::type_traits::isExpensiveToCopy(LoopVar.getType(), Context);
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if (LoopVar.getType().isConstQualified() || !Expensive || !*Expensive)
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return false;
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// We omit the case where the loop variable is not used in the loop body. E.g.
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//
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// for (auto _ : benchmark_state) {
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// }
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//
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// Because the fix (changing to `const auto &`) will introduce an unused
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// compiler warning which can't be suppressed.
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// Since this case is very rare, it is safe to ignore it.
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if (!ExprMutationAnalyzer(*ForRange.getBody(), Context).isMutated(&LoopVar) &&
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!utils::decl_ref_expr::allDeclRefExprs(LoopVar, *ForRange.getBody(),
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Context)
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.empty()) {
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diag(LoopVar.getLocation(),
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"loop variable is copied but only used as const reference; consider "
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"making it a const reference")
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<< utils::fixit::changeVarDeclToConst(LoopVar)
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<< utils::fixit::changeVarDeclToReference(LoopVar, Context);
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return true;
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}
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return false;
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}
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} // namespace performance
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} // namespace tidy
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} // namespace clang
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