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 AST_MATCHER_P(Expr, hasParentIgnoringImpCasts,
32               ast_matchers::internal::Matcher<Expr>, InnerMatcher) {
33   const Expr *E = &Node;
34   do {
35     ASTContext::DynTypedNodeList Parents =
36         Finder->getASTContext().getParents(*E);
37     if (Parents.size() != 1)
38       return false;
39     E = Parents[0].get<Expr>();
40     if (!E)
41       return false;
42   } while (isa<ImplicitCastExpr>(E));
43 
44   return InnerMatcher.matches(*E, Finder, Builder);
45 }
46 
47 void ProBoundsArrayToPointerDecayCheck::registerMatchers(MatchFinder *Finder) {
48   if (!getLangOpts().CPlusPlus)
49     return;
50 
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       implicitCastExpr(unless(hasParent(arraySubscriptExpr())),
57                        unless(hasParentIgnoringImpCasts(explicitCastExpr())),
58                        unless(isInsideOfRangeBeginEndStmt()),
59                        unless(hasSourceExpression(stringLiteral())))
60           .bind("cast"),
61       this);
62 }
63 
64 void ProBoundsArrayToPointerDecayCheck::check(
65     const MatchFinder::MatchResult &Result) {
66   const auto *MatchedCast = Result.Nodes.getNodeAs<ImplicitCastExpr>("cast");
67   if (MatchedCast->getCastKind() != CK_ArrayToPointerDecay)
68     return;
69 
70   diag(MatchedCast->getExprLoc(), "do not implicitly decay an array into a "
71                                   "pointer; consider using gsl::array_view or "
72                                   "an explicit cast instead");
73 }
74 
75 } // namespace tidy
76 } // namespace clang
77