clang-tools-extra/clang-tidy/bugprone/UnusedRaiiCheck.cpp

   1 //===--- UnusedRaiiCheck.cpp - clang-tidy ---------------------------------===//
   2 //
   3 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
   4 // See https://llvm.org/LICENSE.txt for license information.
   5 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
   6 //
   7 //===----------------------------------------------------------------------===//
   8
   9 #include "UnusedRaiiCheck.h"
  10 #include "clang/AST/ASTContext.h"
  11 #include "clang/Lex/Lexer.h"
  12
  13 using namespace clang::ast_matchers;
  14
  15 namespace clang::tidy::bugprone {
  16
  17 namespace {
  18 AST_MATCHER(CXXRecordDecl, hasNonTrivialDestructor) {
  19   // TODO: If the dtor is there but empty we don't want to warn either.
  20   return Node.hasDefinition() && Node.hasNonTrivialDestructor();
  21 }
  22 } // namespace
  23
  24 void UnusedRaiiCheck::registerMatchers(MatchFinder *Finder) {
  25   // Look for temporaries that are constructed in-place and immediately
  26   // destroyed.
  27   Finder->addMatcher(
  28       mapAnyOf(cxxConstructExpr, cxxUnresolvedConstructExpr)
  29           .with(hasParent(compoundStmt().bind("compound")),
  30                 anyOf(hasType(hasCanonicalType(recordType(hasDeclaration(
  31                           cxxRecordDecl(hasNonTrivialDestructor()))))),
  32                       hasType(hasCanonicalType(templateSpecializationType(
  33                           hasDeclaration(classTemplateDecl(has(
  34                               cxxRecordDecl(hasNonTrivialDestructor())))))))))
  35           .bind("expr"),
  36       this);
  37 }
  38
  39 template <typename T>
  40 void reportDiagnostic(DiagnosticBuilder D, const T *Node, SourceRange SR,
  41                       bool DefaultConstruction) {
  42   const char *Replacement = " give_me_a_name";
  43
  44   // If this is a default ctor we have to remove the parens or we'll introduce a
  45   // most vexing parse.
  46   if (DefaultConstruction) {
  47     D << FixItHint::CreateReplacement(CharSourceRange::getTokenRange(SR),
  48                                       Replacement);
  49     return;
  50   }
  51
  52   // Otherwise just suggest adding a name. To find the place to insert the name
  53   // find the first TypeLoc in the children of E, which always points to the
  54   // written type.
  55   D << FixItHint::CreateInsertion(SR.getBegin(), Replacement);
  56 }
  57
  58 void UnusedRaiiCheck::check(const MatchFinder::MatchResult &Result) {
  59   const auto *E = Result.Nodes.getNodeAs<Expr>("expr");
  60
  61   // We ignore code expanded from macros to reduce the number of false
  62   // positives.
  63   if (E->getBeginLoc().isMacroID())
  64     return;
  65
  66   // Don't emit a warning for the last statement in the surrounding compound
  67   // statement.
  68   const auto *CS = Result.Nodes.getNodeAs<CompoundStmt>("compound");
  69   const auto *LastExpr = dyn_cast<Expr>(CS->body_back());
  70
  71   if (LastExpr && E == LastExpr->IgnoreUnlessSpelledInSource())
  72     return;
  73
  74   // Emit a warning.
  75   auto D = diag(E->getBeginLoc(), "object destroyed immediately after "
  76                                   "creation; did you mean to name the object?");
  77
  78   if (const auto *Node = dyn_cast<CXXConstructExpr>(E))
  79     reportDiagnostic(D, Node, Node->getParenOrBraceRange(),
  80                      Node->getNumArgs() == 0 ||
  81                          isa<CXXDefaultArgExpr>(Node->getArg(0)));
  82   if (const auto *Node = dyn_cast<CXXUnresolvedConstructExpr>(E)) {
  83     auto SR = SourceRange(Node->getLParenLoc(), Node->getRParenLoc());
  84     auto DefaultConstruction = Node->getNumArgs() == 0;
  85     if (!DefaultConstruction) {
  86       auto *FirstArg = Node->getArg(0);
  87       DefaultConstruction = isa<CXXDefaultArgExpr>(FirstArg);
  88       if (auto *ILE = dyn_cast<InitListExpr>(FirstArg)) {
  89         DefaultConstruction = ILE->getNumInits() == 0;
  90         SR = SourceRange(ILE->getLBraceLoc(), ILE->getRBraceLoc());
  91       }
  92     }
  93     reportDiagnostic(D, Node, SR, DefaultConstruction);
  94   }
  95 }
  96
  97 } // namespace clang::tidy::bugprone