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 namespace cppcoreguidelines {
19 
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 
28 AST_MATCHER(Stmt, isInsideOfRangeBeginEndStmt) {
29   return stmt(hasAncestor(cxxForRangeStmt(
30                   hasRangeBeginEndStmt(hasDescendant(equalsNode(&Node))))))
31       .matches(Node, Finder, Builder);
32 }
33 
34 AST_MATCHER_P(Expr, hasParentIgnoringImpCasts,
35               ast_matchers::internal::Matcher<Expr>, InnerMatcher) {
36   const Expr *E = &Node;
37   do {
38     ASTContext::DynTypedNodeList Parents =
39         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 
50 void ProBoundsArrayToPointerDecayCheck::registerMatchers(MatchFinder *Finder) {
51   if (!getLangOpts().CPlusPlus)
52     return;
53 
54   // The only allowed array to pointer decay
55   // 1) just before array subscription
56   // 2) inside a range-for over an array
57   // 3) if it converts a string literal to a pointer
58   Finder->addMatcher(
59       implicitCastExpr(unless(hasParent(arraySubscriptExpr())),
60                        unless(hasParentIgnoringImpCasts(explicitCastExpr())),
61                        unless(isInsideOfRangeBeginEndStmt()),
62                        unless(hasSourceExpression(stringLiteral())))
63           .bind("cast"),
64       this);
65 }
66 
67 void ProBoundsArrayToPointerDecayCheck::check(
68     const MatchFinder::MatchResult &Result) {
69   const auto *MatchedCast = Result.Nodes.getNodeAs<ImplicitCastExpr>("cast");
70   if (MatchedCast->getCastKind() != CK_ArrayToPointerDecay)
71     return;
72 
73   diag(MatchedCast->getExprLoc(), "do not implicitly decay an array into a "
74                                   "pointer; consider using gsl::array_view or "
75                                   "an explicit cast instead");
76 }
77 
78 } // namespace cppcoreguidelines
79 } // namespace tidy
80 } // namespace clang
81