AvoidCArraysCheck.cpp

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//===--- AvoidCArraysCheck.cpp - clang-tidy -------------------------------===//
//
// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
// See https://llvm.org/LICENSE.txt for license information.
// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
//
//===----------------------------------------------------------------------===//
 
#include "AvoidCArraysCheck.h"
#include "clang/AST/ASTContext.h"
#include "clang/ASTMatchers/ASTMatchFinder.h"
#include "clang/ASTMatchers/ASTMatchers.h"
 
using namespace clang::ast_matchers;
 
namespace clang::tidy::modernize {
 
namespace {
 
AST_MATCHER(clang::TypeLoc, hasValidBeginLoc) {
  return Node.getBeginLoc().isValid();
}
 
AST_MATCHER_P(clang::TypeLoc, hasType,
              clang::ast_matchers::internal::Matcher<clang::Type>,
              InnerMatcher) {
  const clang::Type *TypeNode = Node.getTypePtr();
  return TypeNode != nullptr &&
         InnerMatcher.matches(*TypeNode, Finder, Builder);
}
 
AST_MATCHER(clang::RecordDecl, isExternCContext) {
  return Node.isExternCContext();
}
 
AST_MATCHER(clang::ParmVarDecl, isArgvOfMain) {
  const clang::DeclContext *DC = Node.getDeclContext();
  const auto *FD = llvm::dyn_cast<clang::FunctionDecl>(DC);
  return FD ? FD->isMain() : false;
}
 
} // namespace
 
AvoidCArraysCheck::AvoidCArraysCheck(StringRef Name, ClangTidyContext *Context)
    : ClangTidyCheck(Name, Context),
      AllowStringArrays(Options.get("AllowStringArrays", false)) {}
 
void AvoidCArraysCheck::storeOptions(ClangTidyOptions::OptionMap &Opts) {
  Options.store(Opts, "AllowStringArrays", AllowStringArrays);
}
 
void AvoidCArraysCheck::registerMatchers(MatchFinder *Finder) {
  ast_matchers::internal::Matcher<TypeLoc> IgnoreStringArrayIfNeededMatcher =
      anything();
  if (AllowStringArrays)
    IgnoreStringArrayIfNeededMatcher =
        unless(typeLoc(loc(hasCanonicalType(incompleteArrayType(
                           hasElementType(isAnyCharacter())))),
                       hasParent(varDecl(hasInitializer(stringLiteral()),
                                         unless(parmVarDecl())))));
 
  Finder->addMatcher(
      typeLoc(hasValidBeginLoc(), hasType(arrayType()),
              optionally(hasParent(parmVarDecl().bind("param_decl"))),
              unless(anyOf(hasParent(parmVarDecl(isArgvOfMain())),
                           hasParent(varDecl(isExternC())),
                           hasParent(fieldDecl(
                               hasParent(recordDecl(isExternCContext())))),
                           hasAncestor(functionDecl(isExternC())))),
              std::move(IgnoreStringArrayIfNeededMatcher))
          .bind("typeloc"),
      this);
}
 
void AvoidCArraysCheck::check(const MatchFinder::MatchResult &Result) {
  const auto *ArrayType = Result.Nodes.getNodeAs<TypeLoc>("typeloc");
  const bool IsInParam =
      Result.Nodes.getNodeAs<ParmVarDecl>("param_decl") != nullptr;
  const bool IsVLA = ArrayType->getTypePtr()->isVariableArrayType();
  enum class RecommendType { Array, Vector, Span };
  llvm::SmallVector<const char *> RecommendTypes{};
  if (IsVLA) {
    RecommendTypes.push_back("'std::vector'");
  } else if (ArrayType->getTypePtr()->isIncompleteArrayType() && IsInParam) {
    // in function parameter, we also don't know the size of
    // IncompleteArrayType.
    if (Result.Context->getLangOpts().CPlusPlus20)
      RecommendTypes.push_back("'std::span'");
    else {
      RecommendTypes.push_back("'std::array'");
      RecommendTypes.push_back("'std::vector'");
    }
  } else {
    RecommendTypes.push_back("'std::array'");
  }
  diag(ArrayType->getBeginLoc(),
       "do not declare %select{C-style|C VLA}0 arrays, use %1 instead")
      << IsVLA << llvm::join(RecommendTypes, " or ");
}
 
} // namespace clang::tidy::modernize