1 //===--- AssertSideEffectCheck.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 "AssertSideEffectCheck.h"
10 #include "clang/AST/ASTContext.h"
11 #include "clang/ASTMatchers/ASTMatchFinder.h"
12 #include "clang/Frontend/CompilerInstance.h"
13 #include "clang/Lex/Lexer.h"
14 #include "llvm/ADT/SmallVector.h"
15 #include "llvm/ADT/StringRef.h"
16 #include "llvm/Support/Casting.h"
17 #include <algorithm>
18 #include <string>
19 
20 using namespace clang::ast_matchers;
21 
22 namespace clang {
23 namespace tidy {
24 namespace bugprone {
25 
26 namespace {
27 
28 AST_MATCHER_P(Expr, hasSideEffect, bool, CheckFunctionCalls) {
29   const Expr *E = &Node;
30 
31   if (const auto *Op = dyn_cast<UnaryOperator>(E)) {
32     UnaryOperator::Opcode OC = Op->getOpcode();
33     return OC == UO_PostInc || OC == UO_PostDec || OC == UO_PreInc ||
34            OC == UO_PreDec;
35   }
36 
37   if (const auto *Op = dyn_cast<BinaryOperator>(E)) {
38     return Op->isAssignmentOp();
39   }
40 
41   if (const auto *OpCallExpr = dyn_cast<CXXOperatorCallExpr>(E)) {
42     OverloadedOperatorKind OpKind = OpCallExpr->getOperator();
43     return OpKind == OO_Equal || OpKind == OO_PlusEqual ||
44            OpKind == OO_MinusEqual || OpKind == OO_StarEqual ||
45            OpKind == OO_SlashEqual || OpKind == OO_AmpEqual ||
46            OpKind == OO_PipeEqual || OpKind == OO_CaretEqual ||
47            OpKind == OO_LessLessEqual || OpKind == OO_GreaterGreaterEqual ||
48            OpKind == OO_PlusPlus || OpKind == OO_MinusMinus ||
49            OpKind == OO_PercentEqual || OpKind == OO_New ||
50            OpKind == OO_Delete || OpKind == OO_Array_New ||
51            OpKind == OO_Array_Delete;
52   }
53 
54   if (const auto *CExpr = dyn_cast<CallExpr>(E)) {
55     bool Result = CheckFunctionCalls;
56     if (const auto *FuncDecl = CExpr->getDirectCallee()) {
57       if (FuncDecl->getDeclName().isIdentifier() &&
58           FuncDecl->getName() == "__builtin_expect") // exceptions come here
59         Result = false;
60       else if (const auto *MethodDecl = dyn_cast<CXXMethodDecl>(FuncDecl))
61         Result &= !MethodDecl->isConst();
62     }
63     return Result;
64   }
65 
66   return isa<CXXNewExpr>(E) || isa<CXXDeleteExpr>(E) || isa<CXXThrowExpr>(E);
67 }
68 
69 } // namespace
70 
71 AssertSideEffectCheck::AssertSideEffectCheck(StringRef Name,
72                                              ClangTidyContext *Context)
73     : ClangTidyCheck(Name, Context),
74       CheckFunctionCalls(Options.get("CheckFunctionCalls", false)),
75       RawAssertList(Options.get("AssertMacros",
76                                 "assert,NSAssert,NSCAssert")) {
77   StringRef(RawAssertList).split(AssertMacros, ",", -1, false);
78 }
79 
80 // The options are explained in AssertSideEffectCheck.h.
81 void AssertSideEffectCheck::storeOptions(ClangTidyOptions::OptionMap &Opts) {
82   Options.store(Opts, "CheckFunctionCalls", CheckFunctionCalls);
83   Options.store(Opts, "AssertMacros", RawAssertList);
84 }
85 
86 void AssertSideEffectCheck::registerMatchers(MatchFinder *Finder) {
87   auto DescendantWithSideEffect =
88       traverse(TK_AsIs, hasDescendant(expr(hasSideEffect(CheckFunctionCalls))));
89   auto ConditionWithSideEffect = hasCondition(DescendantWithSideEffect);
90   Finder->addMatcher(
91       stmt(
92           anyOf(conditionalOperator(ConditionWithSideEffect),
93                 ifStmt(ConditionWithSideEffect),
94                 unaryOperator(hasOperatorName("!"),
95                               hasUnaryOperand(unaryOperator(
96                                   hasOperatorName("!"),
97                                   hasUnaryOperand(DescendantWithSideEffect))))))
98           .bind("condStmt"),
99       this);
100 }
101 
102 void AssertSideEffectCheck::check(const MatchFinder::MatchResult &Result) {
103   const SourceManager &SM = *Result.SourceManager;
104   const LangOptions LangOpts = getLangOpts();
105   SourceLocation Loc = Result.Nodes.getNodeAs<Stmt>("condStmt")->getBeginLoc();
106 
107   StringRef AssertMacroName;
108   while (Loc.isValid() && Loc.isMacroID()) {
109     StringRef MacroName = Lexer::getImmediateMacroName(Loc, SM, LangOpts);
110 
111     // Check if this macro is an assert.
112     if (llvm::is_contained(AssertMacros, MacroName)) {
113       AssertMacroName = MacroName;
114       break;
115     }
116     Loc = SM.getImmediateMacroCallerLoc(Loc);
117   }
118   if (AssertMacroName.empty())
119     return;
120 
121   diag(Loc, "side effect in %0() condition discarded in release builds")
122       << AssertMacroName;
123 }
124 
125 } // namespace bugprone
126 } // namespace tidy
127 } // namespace clang
128