1 //===--- AvoidNonConstGlobalVariablesCheck.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 "AvoidNonConstGlobalVariablesCheck.h"
10 #include "clang/AST/ASTContext.h"
11 #include "clang/ASTMatchers/ASTMatchFinder.h"
12 #include "clang/ASTMatchers/ASTMatchers.h"
13 
14 using namespace clang::ast_matchers;
15 
16 namespace clang {
17 namespace tidy {
18 namespace cppcoreguidelines {
19 
20 namespace {
21 AST_MATCHER(VarDecl, isLocalVarDecl) { return Node.isLocalVarDecl(); }
22 } // namespace
23 
24 void AvoidNonConstGlobalVariablesCheck::registerMatchers(MatchFinder *Finder) {
25   auto GlobalVariable = varDecl(
26       hasGlobalStorage(),
27       unless(anyOf(
28           isLocalVarDecl(), isConstexpr(), hasType(isConstQualified()),
29           hasType(referenceType())))); // References can't be changed, only the
30                                        // data they reference can be changed.
31 
32   auto GlobalReferenceToNonConst =
33       varDecl(hasGlobalStorage(), hasType(referenceType()),
34               unless(hasType(references(qualType(isConstQualified())))));
35 
36   auto GlobalPointerToNonConst =
37       varDecl(hasGlobalStorage(),
38               hasType(pointerType(pointee(unless(isConstQualified())))));
39 
40   Finder->addMatcher(GlobalVariable.bind("non-const_variable"), this);
41   Finder->addMatcher(GlobalReferenceToNonConst.bind("indirection_to_non-const"),
42                      this);
43   Finder->addMatcher(GlobalPointerToNonConst.bind("indirection_to_non-const"),
44                      this);
45 }
46 
47 void AvoidNonConstGlobalVariablesCheck::check(
48     const MatchFinder::MatchResult &Result) {
49 
50   if (const auto *Variable =
51           Result.Nodes.getNodeAs<VarDecl>("non-const_variable")) {
52     diag(Variable->getLocation(), "variable %0 is non-const and globally "
53                                   "accessible, consider making it const")
54         << Variable; // FIXME: Add fix-it hint to Variable
55     // Don't return early, a non-const variable may also be a pointer or
56     // reference to non-const data.
57   }
58 
59   if (const auto *VD =
60           Result.Nodes.getNodeAs<VarDecl>("indirection_to_non-const")) {
61     diag(VD->getLocation(),
62          "variable %0 provides global access to a non-const object; consider "
63          "making the %select{referenced|pointed-to}1 data 'const'")
64         << VD
65         << VD->getType()->isPointerType(); // FIXME: Add fix-it hint to Variable
66   }
67 }
68 
69 } // namespace cppcoreguidelines
70 } // namespace tidy
71 } // namespace clang
72