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//== PointerSortingChecker.cpp --------------------------------- -*- C++ -*--=//
//
// 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
//
//===----------------------------------------------------------------------===//
//
// This file defines PointerSortingChecker which checks for non-determinism
// caused due to sorting containers with pointer-like elements.
//
//===----------------------------------------------------------------------===//
#include "clang/ASTMatchers/ASTMatchFinder.h"
#include "clang/StaticAnalyzer/Checkers/BuiltinCheckerRegistration.h"
#include "clang/StaticAnalyzer/Core/Checker.h"
#include "clang/StaticAnalyzer/Core/PathSensitive/CheckerContext.h"
using namespace clang;
using namespace ento;
using namespace ast_matchers;
namespace {
// ID of a node at which the diagnostic would be emitted.
constexpr llvm::StringLiteral WarnAtNode = "sort";
class PointerSortingChecker : public Checker<check::ASTCodeBody> {
public:
void checkASTCodeBody(const Decl *D,
AnalysisManager &AM,
BugReporter &BR) const;
};
static void emitDiagnostics(const BoundNodes &Match, const Decl *D,
BugReporter &BR, AnalysisManager &AM,
const PointerSortingChecker *Checker) {
auto *ADC = AM.getAnalysisDeclContext(D);
const auto *MarkedStmt = Match.getNodeAs<CallExpr>(WarnAtNode);
assert(MarkedStmt);
auto Range = MarkedStmt->getSourceRange();
auto Location = PathDiagnosticLocation::createBegin(MarkedStmt,
BR.getSourceManager(),
ADC);
std::string Diagnostics;
llvm::raw_string_ostream OS(Diagnostics);
OS << "Sorting pointer-like elements "
<< "can result in non-deterministic ordering";
BR.EmitBasicReport(ADC->getDecl(), Checker,
"Sorting of pointer-like elements", "Non-determinism",
OS.str(), Location, Range);
}
decltype(auto) callsName(const char *FunctionName) {
return callee(functionDecl(hasName(FunctionName)));
}
// FIXME: Currently we simply check if std::sort is used with pointer-like
// elements. This approach can have a big false positive rate. Using std::sort,
// std::unique and then erase is common technique for deduplicating a container
// (which in some cases might even be quicker than using, let's say std::set).
// In case a container contains arbitrary memory addresses (e.g. multiple
// things give different stuff but might give the same thing multiple times)
// which we don't want to do things with more than once, we might use
// sort-unique-erase and the sort call will emit a report.
auto matchSortWithPointers() -> decltype(decl()) {
// Match any of these function calls.
auto SortFuncM = anyOf(
callsName("std::is_sorted"),
callsName("std::nth_element"),
callsName("std::partial_sort"),
callsName("std::partition"),
callsName("std::sort"),
callsName("std::stable_partition"),
callsName("std::stable_sort")
);
// Match only if the container has pointer-type elements.
auto IteratesPointerEltsM = hasArgument(0,
hasType(cxxRecordDecl(has(
fieldDecl(hasType(hasCanonicalType(
pointsTo(hasCanonicalType(pointerType()))
)))
))));
auto PointerSortM = traverse(
TK_AsIs,
stmt(callExpr(allOf(SortFuncM, IteratesPointerEltsM))).bind(WarnAtNode));
return decl(forEachDescendant(PointerSortM));
}
void PointerSortingChecker::checkASTCodeBody(const Decl *D,
AnalysisManager &AM,
BugReporter &BR) const {
auto MatcherM = matchSortWithPointers();
auto Matches = match(MatcherM, *D, AM.getASTContext());
for (const auto &Match : Matches)
emitDiagnostics(Match, D, BR, AM, this);
}
} // end of anonymous namespace
void ento::registerPointerSortingChecker(CheckerManager &Mgr) {
Mgr.registerChecker<PointerSortingChecker>();
}
bool ento::shouldRegisterPointerSortingChecker(const CheckerManager &mgr) {
const LangOptions &LO = mgr.getLangOpts();
return LO.CPlusPlus;
}
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