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//===--- SuspiciousStringCompareCheck.cpp - clang-tidy---------------------===//
//
// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
// See https://llvm.org/LICENSE.txt for license information.
// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
//
//===----------------------------------------------------------------------===//
#include "SuspiciousStringCompareCheck.h"
#include "../utils/Matchers.h"
#include "../utils/OptionsUtils.h"
#include "clang/AST/ASTContext.h"
#include "clang/ASTMatchers/ASTMatchFinder.h"
#include "clang/Lex/Lexer.h"
using namespace clang::ast_matchers;
namespace clang::tidy::bugprone {
// Semicolon separated list of known string compare-like functions. The list
// must ends with a semicolon.
static const char KnownStringCompareFunctions[] = "__builtin_memcmp;"
"__builtin_strcasecmp;"
"__builtin_strcmp;"
"__builtin_strncasecmp;"
"__builtin_strncmp;"
"_mbscmp;"
"_mbscmp_l;"
"_mbsicmp;"
"_mbsicmp_l;"
"_mbsnbcmp;"
"_mbsnbcmp_l;"
"_mbsnbicmp;"
"_mbsnbicmp_l;"
"_mbsncmp;"
"_mbsncmp_l;"
"_mbsnicmp;"
"_mbsnicmp_l;"
"_memicmp;"
"_memicmp_l;"
"_stricmp;"
"_stricmp_l;"
"_strnicmp;"
"_strnicmp_l;"
"_wcsicmp;"
"_wcsicmp_l;"
"_wcsnicmp;"
"_wcsnicmp_l;"
"lstrcmp;"
"lstrcmpi;"
"memcmp;"
"memicmp;"
"strcasecmp;"
"strcmp;"
"strcmpi;"
"stricmp;"
"strncasecmp;"
"strncmp;"
"strnicmp;"
"wcscasecmp;"
"wcscmp;"
"wcsicmp;"
"wcsncmp;"
"wcsnicmp;"
"wmemcmp;";
SuspiciousStringCompareCheck::SuspiciousStringCompareCheck(
StringRef Name, ClangTidyContext *Context)
: ClangTidyCheck(Name, Context),
WarnOnImplicitComparison(Options.get("WarnOnImplicitComparison", true)),
WarnOnLogicalNotComparison(
Options.get("WarnOnLogicalNotComparison", false)),
StringCompareLikeFunctions(
Options.get("StringCompareLikeFunctions", "")) {}
void SuspiciousStringCompareCheck::storeOptions(
ClangTidyOptions::OptionMap &Opts) {
Options.store(Opts, "WarnOnImplicitComparison", WarnOnImplicitComparison);
Options.store(Opts, "WarnOnLogicalNotComparison", WarnOnLogicalNotComparison);
Options.store(Opts, "StringCompareLikeFunctions", StringCompareLikeFunctions);
}
void SuspiciousStringCompareCheck::registerMatchers(MatchFinder *Finder) {
// Match relational operators.
const auto ComparisonUnaryOperator = unaryOperator(hasOperatorName("!"));
const auto ComparisonBinaryOperator = binaryOperator(isComparisonOperator());
const auto ComparisonOperator =
expr(anyOf(ComparisonUnaryOperator, ComparisonBinaryOperator));
// Add the list of known string compare-like functions and add user-defined
// functions.
std::vector<StringRef> FunctionNames = utils::options::parseListPair(
KnownStringCompareFunctions, StringCompareLikeFunctions);
// Match a call to a string compare functions.
const auto FunctionCompareDecl =
functionDecl(hasAnyName(FunctionNames)).bind("decl");
const auto DirectStringCompareCallExpr =
callExpr(hasDeclaration(FunctionCompareDecl)).bind("call");
const auto MacroStringCompareCallExpr = conditionalOperator(anyOf(
hasTrueExpression(ignoringParenImpCasts(DirectStringCompareCallExpr)),
hasFalseExpression(ignoringParenImpCasts(DirectStringCompareCallExpr))));
// The implicit cast is not present in C.
const auto StringCompareCallExpr = ignoringParenImpCasts(
anyOf(DirectStringCompareCallExpr, MacroStringCompareCallExpr));
if (WarnOnImplicitComparison) {
// Detect suspicious calls to string compare:
// 'if (strcmp())' -> 'if (strcmp() != 0)'
Finder->addMatcher(
stmt(anyOf(mapAnyOf(ifStmt, whileStmt, doStmt, forStmt)
.with(hasCondition(StringCompareCallExpr)),
binaryOperator(hasAnyOperatorName("&&", "||"),
hasEitherOperand(StringCompareCallExpr))))
.bind("missing-comparison"),
this);
}
if (WarnOnLogicalNotComparison) {
// Detect suspicious calls to string compared with '!' operator:
// 'if (!strcmp())' -> 'if (strcmp() == 0)'
Finder->addMatcher(unaryOperator(hasOperatorName("!"),
hasUnaryOperand(ignoringParenImpCasts(
StringCompareCallExpr)))
.bind("logical-not-comparison"),
this);
}
// Detect suspicious cast to an inconsistent type (i.e. not integer type).
Finder->addMatcher(
traverse(TK_AsIs,
implicitCastExpr(unless(hasType(isInteger())),
hasSourceExpression(StringCompareCallExpr))
.bind("invalid-conversion")),
this);
// Detect suspicious operator with string compare function as operand.
Finder->addMatcher(
binaryOperator(unless(anyOf(isComparisonOperator(), hasOperatorName("&&"),
hasOperatorName("||"), hasOperatorName("="))),
hasEitherOperand(StringCompareCallExpr))
.bind("suspicious-operator"),
this);
// Detect comparison to invalid constant: 'strcmp() == -1'.
const auto InvalidLiteral = ignoringParenImpCasts(
anyOf(integerLiteral(unless(equals(0))),
unaryOperator(
hasOperatorName("-"),
has(ignoringParenImpCasts(integerLiteral(unless(equals(0)))))),
characterLiteral(), cxxBoolLiteral()));
Finder->addMatcher(
binaryOperator(isComparisonOperator(),
hasOperands(StringCompareCallExpr, InvalidLiteral))
.bind("invalid-comparison"),
this);
}
void SuspiciousStringCompareCheck::check(
const MatchFinder::MatchResult &Result) {
const auto *Decl = Result.Nodes.getNodeAs<FunctionDecl>("decl");
const auto *Call = Result.Nodes.getNodeAs<CallExpr>("call");
assert(Decl != nullptr && Call != nullptr);
if (Result.Nodes.getNodeAs<Stmt>("missing-comparison")) {
SourceLocation EndLoc = Lexer::getLocForEndOfToken(
Call->getRParenLoc(), 0, Result.Context->getSourceManager(),
getLangOpts());
diag(Call->getBeginLoc(),
"function %0 is called without explicitly comparing result")
<< Decl << FixItHint::CreateInsertion(EndLoc, " != 0");
}
if (const auto *E = Result.Nodes.getNodeAs<Expr>("logical-not-comparison")) {
SourceLocation EndLoc = Lexer::getLocForEndOfToken(
Call->getRParenLoc(), 0, Result.Context->getSourceManager(),
getLangOpts());
SourceLocation NotLoc = E->getBeginLoc();
diag(Call->getBeginLoc(),
"function %0 is compared using logical not operator")
<< Decl
<< FixItHint::CreateRemoval(
CharSourceRange::getTokenRange(NotLoc, NotLoc))
<< FixItHint::CreateInsertion(EndLoc, " == 0");
}
if (Result.Nodes.getNodeAs<Stmt>("invalid-comparison")) {
diag(Call->getBeginLoc(),
"function %0 is compared to a suspicious constant")
<< Decl;
}
if (const auto *BinOp =
Result.Nodes.getNodeAs<BinaryOperator>("suspicious-operator")) {
diag(Call->getBeginLoc(), "results of function %0 used by operator '%1'")
<< Decl << BinOp->getOpcodeStr();
}
if (Result.Nodes.getNodeAs<Stmt>("invalid-conversion")) {
diag(Call->getBeginLoc(), "function %0 has suspicious implicit cast")
<< Decl;
}
}
} // namespace clang::tidy::bugprone
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