1 //===--- ProBoundsArrayToPointerDecayCheck.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 "ProBoundsArrayToPointerDecayCheck.h"
10 #include "clang/AST/ASTContext.h"
11 #include "clang/AST/ParentMapContext.h"
12 #include "clang/ASTMatchers/ASTMatchFinder.h"
13
14 using namespace clang::ast_matchers;
15
16 namespace clang {
17 namespace tidy {
18 namespace cppcoreguidelines {
19
20 namespace {
AST_MATCHER_P(CXXForRangeStmt,hasRangeBeginEndStmt,ast_matchers::internal::Matcher<DeclStmt>,InnerMatcher)21 AST_MATCHER_P(CXXForRangeStmt, hasRangeBeginEndStmt,
22 ast_matchers::internal::Matcher<DeclStmt>, InnerMatcher) {
23 for (const DeclStmt *Stmt : {Node.getBeginStmt(), Node.getEndStmt()})
24 if (Stmt != nullptr && InnerMatcher.matches(*Stmt, Finder, Builder))
25 return true;
26 return false;
27 }
28
AST_MATCHER(Stmt,isInsideOfRangeBeginEndStmt)29 AST_MATCHER(Stmt, isInsideOfRangeBeginEndStmt) {
30 return stmt(hasAncestor(cxxForRangeStmt(
31 hasRangeBeginEndStmt(hasDescendant(equalsNode(&Node))))))
32 .matches(Node, Finder, Builder);
33 }
34
AST_MATCHER_P(Expr,hasParentIgnoringImpCasts,ast_matchers::internal::Matcher<Expr>,InnerMatcher)35 AST_MATCHER_P(Expr, hasParentIgnoringImpCasts,
36 ast_matchers::internal::Matcher<Expr>, InnerMatcher) {
37 const Expr *E = &Node;
38 do {
39 DynTypedNodeList Parents = Finder->getASTContext().getParents(*E);
40 if (Parents.size() != 1)
41 return false;
42 E = Parents[0].get<Expr>();
43 if (!E)
44 return false;
45 } while (isa<ImplicitCastExpr>(E));
46
47 return InnerMatcher.matches(*E, Finder, Builder);
48 }
49 } // namespace
50
registerMatchers(MatchFinder * Finder)51 void ProBoundsArrayToPointerDecayCheck::registerMatchers(MatchFinder *Finder) {
52 // The only allowed array to pointer decay
53 // 1) just before array subscription
54 // 2) inside a range-for over an array
55 // 3) if it converts a string literal to a pointer
56 Finder->addMatcher(
57 traverse(
58 TK_AsIs,
59 implicitCastExpr(
60 unless(hasParent(arraySubscriptExpr())),
61 unless(hasParentIgnoringImpCasts(explicitCastExpr())),
62 unless(isInsideOfRangeBeginEndStmt()),
63 unless(hasSourceExpression(ignoringParens(stringLiteral()))),
64 unless(hasSourceExpression(ignoringParens(conditionalOperator(
65 allOf(hasTrueExpression(stringLiteral()),
66 hasFalseExpression(stringLiteral())))))))
67 .bind("cast")),
68 this);
69 }
70
check(const MatchFinder::MatchResult & Result)71 void ProBoundsArrayToPointerDecayCheck::check(
72 const MatchFinder::MatchResult &Result) {
73 const auto *MatchedCast = Result.Nodes.getNodeAs<ImplicitCastExpr>("cast");
74 if (MatchedCast->getCastKind() != CK_ArrayToPointerDecay)
75 return;
76
77 diag(MatchedCast->getExprLoc(), "do not implicitly decay an array into a "
78 "pointer; consider using gsl::array_view or "
79 "an explicit cast instead");
80 }
81
82 } // namespace cppcoreguidelines
83 } // namespace tidy
84 } // namespace clang
85