1 //===--- ProBoundsArrayToPointerDecayCheck.cpp - clang-tidy----------------===//
2 //
3 //                     The LLVM Compiler Infrastructure
4 //
5 // This file is distributed under the University of Illinois Open Source
6 // License. See LICENSE.TXT for details.
7 //
8 //===----------------------------------------------------------------------===//
9 
10 #include "ProBoundsArrayToPointerDecayCheck.h"
11 #include "clang/AST/ASTContext.h"
12 #include "clang/ASTMatchers/ASTMatchFinder.h"
13 
14 using namespace clang::ast_matchers;
15 
16 namespace clang {
17 namespace tidy {
18 
19 AST_MATCHER_P(CXXForRangeStmt, hasRangeBeginEndStmt,
20               ast_matchers::internal::Matcher<DeclStmt>, InnerMatcher) {
21   const DeclStmt *const Stmt = Node.getBeginEndStmt();
22   return (Stmt != nullptr && InnerMatcher.matches(*Stmt, Finder, Builder));
23 }
24 
25 AST_MATCHER(Stmt, isInsideOfRangeBeginEndStmt) {
26   return stmt(hasAncestor(cxxForRangeStmt(
27                   hasRangeBeginEndStmt(hasDescendant(equalsNode(&Node))))))
28       .matches(Node, Finder, Builder);
29 }
30 
31 void ProBoundsArrayToPointerDecayCheck::registerMatchers(MatchFinder *Finder) {
32   if (!getLangOpts().CPlusPlus)
33     return;
34 
35   // The only allowed array to pointer decay
36   // 1) just before array subscription
37   // 2) inside a range-for over an array
38   // 3) if it converts a string literal to a pointer
39   Finder->addMatcher(
40       implicitCastExpr(unless(hasParent(arraySubscriptExpr())),
41                        unless(hasParent(explicitCastExpr())),
42                        unless(isInsideOfRangeBeginEndStmt()),
43                        unless(hasSourceExpression(stringLiteral())))
44           .bind("cast"),
45       this);
46 }
47 
48 void ProBoundsArrayToPointerDecayCheck::check(
49     const MatchFinder::MatchResult &Result) {
50   const auto *MatchedCast = Result.Nodes.getNodeAs<ImplicitCastExpr>("cast");
51   if (MatchedCast->getCastKind() != CK_ArrayToPointerDecay)
52     return;
53 
54   diag(MatchedCast->getExprLoc(), "do not implicitly decay an array into a "
55                                   "pointer; consider using gsl::array_view or "
56                                   "an explicit cast instead");
57 }
58 
59 } // namespace tidy
60 } // namespace clang
61