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   for (const DeclStmt *Stmt : {Node.getBeginStmt(), Node.getEndStmt()})
22     if (Stmt != nullptr && InnerMatcher.matches(*Stmt, Finder, Builder))
23       return true;
24   return false;
25 }
26 
27 AST_MATCHER(Stmt, isInsideOfRangeBeginEndStmt) {
28   return stmt(hasAncestor(cxxForRangeStmt(
29                   hasRangeBeginEndStmt(hasDescendant(equalsNode(&Node))))))
30       .matches(Node, Finder, Builder);
31 }
32 
33 AST_MATCHER_P(Expr, hasParentIgnoringImpCasts,
34               ast_matchers::internal::Matcher<Expr>, InnerMatcher) {
35   const Expr *E = &Node;
36   do {
37     ASTContext::DynTypedNodeList Parents =
38         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 
49 void ProBoundsArrayToPointerDecayCheck::registerMatchers(MatchFinder *Finder) {
50   if (!getLangOpts().CPlusPlus)
51     return;
52 
53   // The only allowed array to pointer decay
54   // 1) just before array subscription
55   // 2) inside a range-for over an array
56   // 3) if it converts a string literal to a pointer
57   Finder->addMatcher(
58       implicitCastExpr(unless(hasParent(arraySubscriptExpr())),
59                        unless(hasParentIgnoringImpCasts(explicitCastExpr())),
60                        unless(isInsideOfRangeBeginEndStmt()),
61                        unless(hasSourceExpression(stringLiteral())))
62           .bind("cast"),
63       this);
64 }
65 
66 void ProBoundsArrayToPointerDecayCheck::check(
67     const MatchFinder::MatchResult &Result) {
68   const auto *MatchedCast = Result.Nodes.getNodeAs<ImplicitCastExpr>("cast");
69   if (MatchedCast->getCastKind() != CK_ArrayToPointerDecay)
70     return;
71 
72   diag(MatchedCast->getExprLoc(), "do not implicitly decay an array into a "
73                                   "pointer; consider using gsl::array_view or "
74                                   "an explicit cast instead");
75 }
76 
77 } // namespace tidy
78 } // namespace clang
79