1 //===--- ComparisonInTempFailureRetryCheck.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 "../utils/Matchers.h"
10 #include "ComparisonInTempFailureRetryCheck.h"
11 #include "clang/AST/ASTContext.h"
12 #include "clang/ASTMatchers/ASTMatchFinder.h"
13 #include "clang/Lex/Lexer.h"
14 
15 using namespace clang::ast_matchers;
16 
17 namespace clang {
18 namespace tidy {
19 namespace android {
20 
21 namespace {
22 AST_MATCHER(BinaryOperator, isRHSATempFailureRetryArg) {
23   if (!Node.getBeginLoc().isMacroID())
24     return false;
25 
26   const SourceManager &SM = Finder->getASTContext().getSourceManager();
27   if (!SM.isMacroArgExpansion(Node.getRHS()->IgnoreParenCasts()->getBeginLoc()))
28     return false;
29 
30   const LangOptions &Opts = Finder->getASTContext().getLangOpts();
31   SourceLocation LocStart = Node.getBeginLoc();
32   while (LocStart.isMacroID()) {
33     SourceLocation Invocation = SM.getImmediateMacroCallerLoc(LocStart);
34     Token Tok;
35     if (!Lexer::getRawToken(SM.getSpellingLoc(Invocation), Tok, SM, Opts,
36                             /*IgnoreWhiteSpace=*/true)) {
37       if (Tok.getKind() == tok::raw_identifier &&
38           Tok.getRawIdentifier() == "TEMP_FAILURE_RETRY")
39         return true;
40     }
41 
42     LocStart = Invocation;
43   }
44   return false;
45 }
46 } // namespace
47 
48 void ComparisonInTempFailureRetryCheck::registerMatchers(MatchFinder *Finder) {
49   // Both glibc's and Bionic's TEMP_FAILURE_RETRY macros structurally look like:
50   //
51   // #define TEMP_FAILURE_RETRY(x) ({ \
52   //    typeof(x) y; \
53   //    do y = (x); \
54   //    while (y == -1 && errno == EINTR); \
55   //    y; \
56   // })
57   //
58   // (glibc uses `long int` instead of `typeof(x)` for the type of y).
59   //
60   // It's unclear how to walk up the AST from inside the expansion of `x`, and
61   // we need to not complain about things like TEMP_FAILURE_RETRY(foo(x == 1)),
62   // so we just match the assignment of `y = (x)` and inspect `x` from there.
63   Finder->addMatcher(
64       binaryOperator(
65           hasOperatorName("="),
66           hasRHS(ignoringParenCasts(
67               binaryOperator(matchers::isComparisonOperator()).bind("binop"))),
68           isRHSATempFailureRetryArg()),
69       this);
70 }
71 
72 void ComparisonInTempFailureRetryCheck::check(
73     const MatchFinder::MatchResult &Result) {
74   const auto &BinOp = *Result.Nodes.getNodeAs<BinaryOperator>("binop");
75   diag(BinOp.getOperatorLoc(), "top-level comparison in TEMP_FAILURE_RETRY");
76 
77   // FIXME: FixIts would be nice, but potentially nontrivial when nested macros
78   // happen, e.g. `TEMP_FAILURE_RETRY(IS_ZERO(foo()))`
79 }
80 
81 } // namespace android
82 } // namespace tidy
83 } // namespace clang
84