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//=- RunLoopAutoreleaseLeakChecker.cpp --------------------------*- C++ -*-==//
//
// The LLVM Compiler Infrastructure
//
// This file is distributed under the University of Illinois Open Source
// License. See LICENSE.TXT for details.
//
//
//===----------------------------------------------------------------------===//
//
// A checker for detecting leaks resulting from allocating temporary
// autoreleased objects before starting the main run loop.
//
// Checks for two antipatterns:
// 1. ObjCMessageExpr followed by [[NSRunLoop mainRunLoop] run] in the same
// autorelease pool.
// 2. ObjCMessageExpr followed by [[NSRunLoop mainRunLoop] run] in no
// autorelease pool.
//
// Any temporary objects autoreleased in code called in those expressions
// will not be deallocated until the program exits, and are effectively leaks.
//
//===----------------------------------------------------------------------===//
//
#include "clang/StaticAnalyzer/Checkers/BuiltinCheckerRegistration.h"
#include "clang/AST/Decl.h"
#include "clang/AST/DeclObjC.h"
#include "clang/ASTMatchers/ASTMatchFinder.h"
#include "clang/StaticAnalyzer/Core/BugReporter/BugReporter.h"
#include "clang/StaticAnalyzer/Core/BugReporter/BugType.h"
#include "clang/StaticAnalyzer/Core/Checker.h"
#include "clang/StaticAnalyzer/Core/CheckerManager.h"
#include "clang/StaticAnalyzer/Core/PathSensitive/CallEvent.h"
#include "clang/StaticAnalyzer/Core/PathSensitive/CheckerContext.h"
#include "clang/StaticAnalyzer/Core/PathSensitive/ExprEngine.h"
using namespace clang;
using namespace ento;
using namespace ast_matchers;
namespace {
const char * RunLoopBind = "NSRunLoopM";
const char * RunLoopRunBind = "RunLoopRunM";
const char * OtherMsgBind = "OtherMessageSentM";
const char * AutoreleasePoolBind = "AutoreleasePoolM";
const char * OtherStmtAutoreleasePoolBind = "OtherAutoreleasePoolM";
class RunLoopAutoreleaseLeakChecker : public Checker<check::ASTCodeBody> {
public:
void checkASTCodeBody(const Decl *D,
AnalysisManager &AM,
BugReporter &BR) const;
};
} // end anonymous namespace
/// \return Whether {@code A} occurs before {@code B} in traversal of
/// {@code Parent}.
/// Conceptually a very incomplete/unsound approximation of happens-before
/// relationship (A is likely to be evaluated before B),
/// but useful enough in this case.
static bool seenBefore(const Stmt *Parent, const Stmt *A, const Stmt *B) {
for (const Stmt *C : Parent->children()) {
if (!C) continue;
if (C == A)
return true;
if (C == B)
return false;
return seenBefore(C, A, B);
}
return false;
}
static void emitDiagnostics(BoundNodes &Match,
const Decl *D,
BugReporter &BR,
AnalysisManager &AM,
const RunLoopAutoreleaseLeakChecker *Checker) {
assert(D->hasBody());
const Stmt *DeclBody = D->getBody();
AnalysisDeclContext *ADC = AM.getAnalysisDeclContext(D);
const auto *ME = Match.getNodeAs<ObjCMessageExpr>(OtherMsgBind);
assert(ME);
const auto *AP =
Match.getNodeAs<ObjCAutoreleasePoolStmt>(AutoreleasePoolBind);
const auto *OAP =
Match.getNodeAs<ObjCAutoreleasePoolStmt>(OtherStmtAutoreleasePoolBind);
bool HasAutoreleasePool = (AP != nullptr);
const auto *RL = Match.getNodeAs<ObjCMessageExpr>(RunLoopBind);
const auto *RLR = Match.getNodeAs<Stmt>(RunLoopRunBind);
assert(RLR && "Run loop launch not found");
assert(ME != RLR);
// Launch of run loop occurs before the message-sent expression is seen.
if (seenBefore(DeclBody, RLR, ME))
return;
if (HasAutoreleasePool && (OAP != AP))
return;
PathDiagnosticLocation Location = PathDiagnosticLocation::createBegin(
ME, BR.getSourceManager(), ADC);
SourceRange Range = ME->getSourceRange();
BR.EmitBasicReport(ADC->getDecl(), Checker,
/*Name=*/"Memory leak inside autorelease pool",
/*Category=*/"Memory",
/*Name=*/
(Twine("Temporary objects allocated in the") +
" autorelease pool " +
(HasAutoreleasePool ? "" : "of last resort ") +
"followed by the launch of " +
(RL ? "main run loop " : "xpc_main ") +
"may never get released; consider moving them to a "
"separate autorelease pool")
.str(),
Location, Range);
}
static StatementMatcher getRunLoopRunM(StatementMatcher Extra = anything()) {
StatementMatcher MainRunLoopM =
objcMessageExpr(hasSelector("mainRunLoop"),
hasReceiverType(asString("NSRunLoop")),
Extra)
.bind(RunLoopBind);
StatementMatcher MainRunLoopRunM = objcMessageExpr(hasSelector("run"),
hasReceiver(MainRunLoopM),
Extra).bind(RunLoopRunBind);
StatementMatcher XPCRunM =
callExpr(callee(functionDecl(hasName("xpc_main")))).bind(RunLoopRunBind);
return anyOf(MainRunLoopRunM, XPCRunM);
}
static StatementMatcher getOtherMessageSentM(StatementMatcher Extra = anything()) {
return objcMessageExpr(unless(anyOf(equalsBoundNode(RunLoopBind),
equalsBoundNode(RunLoopRunBind))),
Extra)
.bind(OtherMsgBind);
}
static void
checkTempObjectsInSamePool(const Decl *D, AnalysisManager &AM, BugReporter &BR,
const RunLoopAutoreleaseLeakChecker *Chkr) {
StatementMatcher RunLoopRunM = getRunLoopRunM();
StatementMatcher OtherMessageSentM = getOtherMessageSentM(
hasAncestor(autoreleasePoolStmt().bind(OtherStmtAutoreleasePoolBind)));
StatementMatcher RunLoopInAutorelease =
autoreleasePoolStmt(
hasDescendant(RunLoopRunM),
hasDescendant(OtherMessageSentM)).bind(AutoreleasePoolBind);
DeclarationMatcher GroupM = decl(hasDescendant(RunLoopInAutorelease));
auto Matches = match(GroupM, *D, AM.getASTContext());
for (BoundNodes Match : Matches)
emitDiagnostics(Match, D, BR, AM, Chkr);
}
static void
checkTempObjectsInNoPool(const Decl *D, AnalysisManager &AM, BugReporter &BR,
const RunLoopAutoreleaseLeakChecker *Chkr) {
auto NoPoolM = unless(hasAncestor(autoreleasePoolStmt()));
StatementMatcher RunLoopRunM = getRunLoopRunM(NoPoolM);
StatementMatcher OtherMessageSentM = getOtherMessageSentM(NoPoolM);
DeclarationMatcher GroupM = functionDecl(
isMain(),
hasDescendant(RunLoopRunM),
hasDescendant(OtherMessageSentM)
);
auto Matches = match(GroupM, *D, AM.getASTContext());
for (BoundNodes Match : Matches)
emitDiagnostics(Match, D, BR, AM, Chkr);
}
void RunLoopAutoreleaseLeakChecker::checkASTCodeBody(const Decl *D,
AnalysisManager &AM,
BugReporter &BR) const {
checkTempObjectsInSamePool(D, AM, BR, this);
checkTempObjectsInNoPool(D, AM, BR, this);
}
void ento::registerRunLoopAutoreleaseLeakChecker(CheckerManager &mgr) {
mgr.registerChecker<RunLoopAutoreleaseLeakChecker>();
}
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