1 //===--- MultipleStatementMacroCheck.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 "MultipleStatementMacroCheck.h"
10 #include "clang/AST/ASTContext.h"
11 #include "clang/ASTMatchers/ASTMatchFinder.h"
12 
13 using namespace clang::ast_matchers;
14 
15 namespace clang {
16 namespace tidy {
17 namespace bugprone {
18 
19 namespace {
20 
21 AST_MATCHER(Expr, isInMacro) { return Node.getBeginLoc().isMacroID(); }
22 
23 /// Find the next statement after `S`.
24 const Stmt *nextStmt(const MatchFinder::MatchResult &Result, const Stmt *S) {
25   auto Parents = Result.Context->getParents(*S);
26   if (Parents.empty())
27     return nullptr;
28   const auto *Parent = Parents[0].get<Stmt>();
29   if (!Parent)
30     return nullptr;
31   const Stmt *Prev = nullptr;
32   for (const Stmt *Child : Parent->children()) {
33     if (Prev == S)
34       return Child;
35     Prev = Child;
36   }
37   return nextStmt(Result, Parent);
38 }
39 
40 using ExpansionRanges = std::vector<SourceRange>;
41 
42 /// \bried Get all the macro expansion ranges related to `Loc`.
43 ///
44 /// The result is ordered from most inner to most outer.
45 ExpansionRanges getExpansionRanges(SourceLocation Loc,
46                                    const MatchFinder::MatchResult &Result) {
47   ExpansionRanges Locs;
48   while (Loc.isMacroID()) {
49     Locs.push_back(
50         Result.SourceManager->getImmediateExpansionRange(Loc).getAsRange());
51     Loc = Locs.back().getBegin();
52   }
53   return Locs;
54 }
55 
56 } // namespace
57 
58 void MultipleStatementMacroCheck::registerMatchers(MatchFinder *Finder) {
59   const auto Inner = expr(isInMacro(), unless(compoundStmt())).bind("inner");
60   Finder->addMatcher(
61       stmt(anyOf(ifStmt(hasThen(Inner)), ifStmt(hasElse(Inner)).bind("else"),
62                  whileStmt(hasBody(Inner)), forStmt(hasBody(Inner))))
63           .bind("outer"),
64       this);
65 }
66 
67 void MultipleStatementMacroCheck::check(
68     const MatchFinder::MatchResult &Result) {
69   const auto *Inner = Result.Nodes.getNodeAs<Expr>("inner");
70   const auto *Outer = Result.Nodes.getNodeAs<Stmt>("outer");
71   const auto *Next = nextStmt(Result, Outer);
72   if (!Next)
73     return;
74 
75   SourceLocation OuterLoc = Outer->getBeginLoc();
76   if (Result.Nodes.getNodeAs<Stmt>("else"))
77     OuterLoc = cast<IfStmt>(Outer)->getElseLoc();
78 
79   auto InnerRanges = getExpansionRanges(Inner->getBeginLoc(), Result);
80   auto OuterRanges = getExpansionRanges(OuterLoc, Result);
81   auto NextRanges = getExpansionRanges(Next->getBeginLoc(), Result);
82 
83   // Remove all the common ranges, starting from the top (the last ones in the
84   // list).
85   while (!InnerRanges.empty() && !OuterRanges.empty() && !NextRanges.empty() &&
86          InnerRanges.back() == OuterRanges.back() &&
87          InnerRanges.back() == NextRanges.back()) {
88     InnerRanges.pop_back();
89     OuterRanges.pop_back();
90     NextRanges.pop_back();
91   }
92 
93   // Inner and Next must have at least one more macro that Outer doesn't have,
94   // and that range must be common to both.
95   if (InnerRanges.empty() || NextRanges.empty() ||
96       InnerRanges.back() != NextRanges.back())
97     return;
98 
99   diag(InnerRanges.back().getBegin(), "multiple statement macro used without "
100                                       "braces; some statements will be "
101                                       "unconditionally executed");
102 }
103 
104 } // namespace bugprone
105 } // namespace tidy
106 } // namespace clang
107