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 #include "clang/ASTMatchers/ASTMatchers.h"
14
15 using namespace clang::ast_matchers;
16
17 namespace clang::tidy::cppcoreguidelines {
18
19 namespace {
AST_MATCHER_P(CXXForRangeStmt,hasRangeBeginEndStmt,ast_matchers::internal::Matcher<DeclStmt>,InnerMatcher)20 AST_MATCHER_P(CXXForRangeStmt, hasRangeBeginEndStmt,
21 ast_matchers::internal::Matcher<DeclStmt>, InnerMatcher) {
22 for (const DeclStmt *Stmt : {Node.getBeginStmt(), Node.getEndStmt()})
23 if (Stmt != nullptr && InnerMatcher.matches(*Stmt, Finder, Builder))
24 return true;
25 return false;
26 }
27
AST_MATCHER(Stmt,isInsideOfRangeBeginEndStmt)28 AST_MATCHER(Stmt, isInsideOfRangeBeginEndStmt) {
29 return stmt(hasAncestor(cxxForRangeStmt(
30 hasRangeBeginEndStmt(hasDescendant(equalsNode(&Node))))))
31 .matches(Node, Finder, Builder);
32 }
33
AST_MATCHER_P(Expr,hasParentIgnoringImpCasts,ast_matchers::internal::Matcher<Expr>,InnerMatcher)34 AST_MATCHER_P(Expr, hasParentIgnoringImpCasts,
35 ast_matchers::internal::Matcher<Expr>, InnerMatcher) {
36 const Expr *E = &Node;
37 do {
38 DynTypedNodeList Parents = Finder->getASTContext().getParents(*E);
39 if (Parents.size() != 1)
40 return false;
41 E = Parents[0].get<Expr>();
42 if (!E)
43 return false;
44 } while (isa<ImplicitCastExpr>(E));
45
46 return InnerMatcher.matches(*E, Finder, Builder);
47 }
48 } // namespace
49
registerMatchers(MatchFinder * Finder)50 void ProBoundsArrayToPointerDecayCheck::registerMatchers(MatchFinder *Finder) {
51 // The only allowed array to pointer decay
52 // 1) just before array subscription
53 // 2) inside a range-for over an array
54 // 3) if it converts a string literal to a pointer
55 Finder->addMatcher(
56 traverse(
57 TK_AsIs,
58 implicitCastExpr(
59 unless(hasParent(arraySubscriptExpr())),
60 unless(hasSourceExpression(predefinedExpr())),
61 unless(hasParentIgnoringImpCasts(explicitCastExpr())),
62 unless(isInsideOfRangeBeginEndStmt()),
63 unless(hasSourceExpression(ignoringParens(stringLiteral()))),
64 unless(hasSourceExpression(ignoringParens(
65 conditionalOperator(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 clang::tidy::cppcoreguidelines
83