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[LifetimeSafety] Track gsl::Pointer types
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2 files changed

+293
-21
lines changed

2 files changed

+293
-21
lines changed

‎clang/lib/Analysis/LifetimeSafety.cpp‎

Lines changed: 141 additions & 20 deletions
Original file line numberDiff line numberDiff line change
@@ -419,10 +419,13 @@ class FactGenerator : public ConstStmtVisitor<FactGenerator> {
419419
VisitedStmts.clear();
420420
for (unsigned I = 0; I < Block->size(); ++I) {
421421
const CFGElement &Element = Block->Elements[I];
422-
if (std::optional<CFGStmt> CS = Element.getAs<CFGStmt>())
422+
if (std::optional<CFGStmt> CS = Element.getAs<CFGStmt>()) {
423+
DEBUG_WITH_TYPE("PrintCFG", llvm::dbgs() << " ================== \n");
424+
DEBUG_WITH_TYPE("PrintCFG", CS->dump());
425+
DEBUG_WITH_TYPE("PrintCFG", CS->getStmt()->dumpColor());
423426
Visit(CS->getStmt());
424-
else if (std::optional<CFGAutomaticObjDtor> DtorOpt =
425-
Element.getAs<CFGAutomaticObjDtor>())
427+
} else if (std::optional<CFGAutomaticObjDtor> DtorOpt =
428+
Element.getAs<CFGAutomaticObjDtor>())
426429
handleDestructor(*DtorOpt);
427430
}
428431
FactMgr.addBlockFacts(Block, CurrentBlockFacts);
@@ -443,6 +446,31 @@ class FactGenerator : public ConstStmtVisitor<FactGenerator> {
443446
addAssignOriginFact(*VD, *InitExpr);
444447
}
445448

449+
void VisitCXXConstructExpr(const CXXConstructExpr *CCE) {
450+
if (!isGslPointerType(CCE->getType()))
451+
return;
452+
453+
if (CCE->getNumArgs() > 0 && hasOrigin(CCE->getArg(0)->getType()))
454+
// This is a propagation.
455+
addAssignOriginFact(*CCE, *CCE->getArg(0));
456+
else
457+
// This could be a new borrow.
458+
checkForBorrows(CCE, CCE->getConstructor(),
459+
{CCE->getArgs(), CCE->getNumArgs()});
460+
}
461+
462+
void VisitCXXMemberCallExpr(const CXXMemberCallExpr *MCE) {
463+
if (!isGslPointerType(MCE->getImplicitObjectArgument()->getType()))
464+
return;
465+
// Specifically for conversion operators, like `std::string_view p = a;`
466+
if (isa<CXXConversionDecl>(MCE->getCalleeDecl())) {
467+
// The argument is the implicit object itself.
468+
checkForBorrows(MCE, MCE->getMethodDecl(),
469+
{MCE->getImplicitObjectArgument()});
470+
}
471+
// Note: A more general VisitCallExpr could also be used here.
472+
}
473+
446474
void VisitCXXNullPtrLiteralExpr(const CXXNullPtrLiteralExpr *N) {
447475
/// TODO: Handle nullptr expr as a special 'null' loan. Uninitialized
448476
/// pointers can use the same type of loan.
@@ -495,38 +523,131 @@ class FactGenerator : public ConstStmtVisitor<FactGenerator> {
495523
}
496524

497525
void VisitBinaryOperator(const BinaryOperator *BO) {
498-
if (BO->isAssignmentOp()) {
499-
const Expr *LHSExpr = BO->getLHS();
500-
const Expr *RHSExpr = BO->getRHS();
501-
502-
// We are interested in assignments like `ptr1 = ptr2` or `ptr = &var`
503-
// LHS must be a pointer/reference type that can be an origin.
504-
// RHS must also represent an origin (either another pointer/ref or an
505-
// address-of).
506-
if (const auto *DRE_LHS = dyn_cast<DeclRefExpr>(LHSExpr))
507-
if (const auto *VD_LHS =
508-
dyn_cast<ValueDecl>(DRE_LHS->getDecl()->getCanonicalDecl());
509-
VD_LHS && hasOrigin(VD_LHS->getType()))
510-
addAssignOriginFact(*VD_LHS, *RHSExpr);
511-
}
526+
if (BO->isAssignmentOp())
527+
handleAssignment(BO->getLHS(), BO->getRHS());
528+
}
529+
530+
void VisitCXXOperatorCallExpr(const CXXOperatorCallExpr *OCE) {
531+
if (OCE->isAssignmentOp() && OCE->getNumArgs() == 2)
532+
handleAssignment(OCE->getArg(0), OCE->getArg(1));
512533
}
513534

514535
void VisitCXXFunctionalCastExpr(const CXXFunctionalCastExpr *FCE) {
515536
// Check if this is a test point marker. If so, we are done with this
516537
// expression.
517538
if (VisitTestPoint(FCE))
518539
return;
519-
// Visit as normal otherwise.
520-
Base::VisitCXXFunctionalCastExpr(FCE);
540+
if (isGslPointerType(FCE->getType()))
541+
addAssignOriginFact(*FCE, *FCE->getSubExpr());
542+
}
543+
544+
void VisitInitListExpr(const InitListExpr *ILE) {
545+
if (!hasOrigin(ILE->getType()))
546+
return;
547+
// For list initialization with a single element, like `View{...}`, the
548+
// origin of the list itself is the origin of its single element.
549+
if (ILE->getNumInits() == 1) {
550+
Visit(ILE->getInit(0));
551+
addAssignOriginFact(*ILE, *ILE->getInit(0));
552+
}
553+
}
554+
555+
void VisitMaterializeTemporaryExpr(const MaterializeTemporaryExpr *MTE) {
556+
if (!hasOrigin(MTE->getType()))
557+
return;
558+
// A temporary object's origin is the same as the origin of the
559+
// expression that initializes it.
560+
addAssignOriginFact(*MTE, *MTE->getSubExpr());
521561
}
522562

523563
private:
564+
static bool isGslPointerType(QualType QT) {
565+
if (const auto *RD = QT->getAsCXXRecordDecl()) {
566+
// We need to check the template definition for specializations.
567+
if (auto *CTSD = dyn_cast<ClassTemplateSpecializationDecl>(RD))
568+
return CTSD->getSpecializedTemplate()
569+
->getTemplatedDecl()
570+
->hasAttr<PointerAttr>();
571+
return RD->hasAttr<PointerAttr>();
572+
}
573+
return false;
574+
}
575+
524576
// Check if a type has an origin.
525-
bool hasOrigin(QualType QT) { return QT->isPointerOrReferenceType(); }
577+
static bool hasOrigin(QualType QT) {
578+
if (QT->isFunctionPointerType())
579+
return false;
580+
return QT->isPointerOrReferenceType() || isGslPointerType(QT);
581+
}
582+
583+
/// Checks if a call-like expression creates a borrow by passing a local
584+
/// value to a reference parameter, creating an IssueFact if it does.
585+
void checkForBorrows(const Expr *Call, const FunctionDecl *FD,
586+
ArrayRef<const Expr *> Args) {
587+
if (!FD)
588+
return;
589+
590+
for (unsigned I = 0; I < Args.size(); ++I) {
591+
if (I >= FD->getNumParams())
592+
break;
593+
594+
const ParmVarDecl *Param = FD->getParamDecl(I);
595+
const Expr *Arg = Args[I];
596+
597+
// This is the core condition for a new borrow: a value type (no origin)
598+
// is passed to a reference parameter.
599+
if (Param->getType()->isReferenceType() && !hasOrigin(Arg->getType())) {
600+
if (const Loan *L = createLoanFrom(Arg, Call)) {
601+
OriginID OID = FactMgr.getOriginMgr().getOrCreate(*Call);
602+
CurrentBlockFacts.push_back(
603+
FactMgr.createFact<IssueFact>(L->ID, OID));
604+
// For view creation, we assume the first borrow is the significant
605+
// one.
606+
return;
607+
}
608+
}
609+
}
610+
}
611+
612+
/// Attempts to create a loan by analyzing the source expression of a borrow.
613+
/// This method is the single point for creating loans, allowing for future
614+
/// expansion to handle temporaries, field members, etc.
615+
/// \param SourceExpr The expression representing the object being borrowed
616+
/// from.
617+
/// \param IssueExpr The expression that triggers the borrow (e.g., a
618+
/// constructor call).
619+
/// \return The new Loan on success, nullptr on failure.
620+
const Loan *createLoanFrom(const Expr *SourceExpr, const Expr *IssueExpr) {
621+
// For now, we only handle direct borrows from local variables.
622+
// In the future, this can be extended to handle MaterializeTemporaryExpr,
623+
// etc.
624+
if (const auto *DRE =
625+
dyn_cast<DeclRefExpr>(SourceExpr->IgnoreParenImpCasts())) {
626+
if (const auto *VD = dyn_cast<ValueDecl>(DRE->getDecl())) {
627+
AccessPath Path(VD);
628+
return &FactMgr.getLoanMgr().addLoan(Path, IssueExpr);
629+
}
630+
}
631+
return nullptr;
632+
}
633+
634+
void handleAssignment(const Expr *LHSExpr, const Expr *RHSExpr) {
635+
// Find the underlying variable declaration for the left-hand side.
636+
if (const auto *DRE_LHS =
637+
dyn_cast<DeclRefExpr>(LHSExpr->IgnoreParenImpCasts()))
638+
if (const auto *VD_LHS = dyn_cast<ValueDecl>(DRE_LHS->getDecl()))
639+
if (hasOrigin(VD_LHS->getType()))
640+
// We are interested in assignments like `ptr1 = ptr2` or `ptr = &var`
641+
// LHS must be a pointer/reference type that can be an origin.
642+
// RHS must also represent an origin (either another pointer/ref or an
643+
// address-of).
644+
addAssignOriginFact(*VD_LHS, *RHSExpr);
645+
}
526646

527647
template <typename Destination, typename Source>
528648
void addAssignOriginFact(const Destination &D, const Source &S) {
529649
OriginID DestOID = FactMgr.getOriginMgr().getOrCreate(D);
650+
Visit(&S);
530651
OriginID SrcOID = FactMgr.getOriginMgr().get(S);
531652
CurrentBlockFacts.push_back(
532653
FactMgr.createFact<AssignOriginFact>(DestOID, SrcOID));

‎clang/unittests/Analysis/LifetimeSafetyTest.cpp‎

Lines changed: 152 additions & 1 deletion
Original file line numberDiff line numberDiff line change
@@ -11,7 +11,6 @@
1111
#include "clang/ASTMatchers/ASTMatchers.h"
1212
#include "clang/Testing/TestAST.h"
1313
#include "llvm/ADT/StringMap.h"
14-
#include "llvm/Testing/Support/Error.h"
1514
#include "gmock/gmock.h"
1615
#include "gtest/gtest.h"
1716
#include <optional>
@@ -31,7 +30,13 @@ class LifetimeTestRunner {
3130
LifetimeTestRunner(llvm::StringRef Code) {
3231
std::string FullCode = R"(
3332
#define POINT(name) void("__lifetime_test_point_" #name)
33+
3434
struct MyObj { ~MyObj() {} int i; };
35+
36+
struct [[gsl::Pointer()]] View {
37+
View(const MyObj&);
38+
View();
39+
};
3540
)";
3641
FullCode += Code.str();
3742

@@ -741,5 +746,151 @@ TEST_F(LifetimeAnalysisTest, NoDuplicateLoansForImplicitCastToConst) {
741746
EXPECT_THAT(Helper->getLoansForVar("a"), SizeIs(2));
742747
}
743748

749+
TEST_F(LifetimeAnalysisTest, GslPointerSimpleLoan) {
750+
SetupTest(R"(
751+
void target() {
752+
MyObj a;
753+
View x = a;
754+
POINT(p1);
755+
}
756+
)");
757+
EXPECT_THAT(Origin("x"), HasLoansTo({"a"}, "p1"));
758+
}
759+
760+
TEST_F(LifetimeAnalysisTest, GslPointerConstructFromOwner) {
761+
SetupTest(R"(
762+
void target() {
763+
MyObj al, bl, cl, dl, el;
764+
View a = View(al);
765+
View b = View{bl};
766+
View c = View(View(View(cl)));
767+
View d = View{View(View(dl))};
768+
View e = View{View{View{el}}};
769+
POINT(p1);
770+
}
771+
)");
772+
EXPECT_THAT(Origin("a"), HasLoansTo({"al"}, "p1"));
773+
EXPECT_THAT(Origin("b"), HasLoansTo({"bl"}, "p1"));
774+
EXPECT_THAT(Origin("c"), HasLoansTo({"cl"}, "p1"));
775+
EXPECT_THAT(Origin("d"), HasLoansTo({"dl"}, "p1"));
776+
EXPECT_THAT(Origin("e"), HasLoansTo({"el"}, "p1"));
777+
}
778+
779+
TEST_F(LifetimeAnalysisTest, GslPointerConstructFromView) {
780+
SetupTest(R"(
781+
void target() {
782+
MyObj a;
783+
View x = View(a);
784+
View y = View{x};
785+
View z = View(View(View(y)));
786+
View p = View{View(View(x))};
787+
POINT(p1);
788+
}
789+
)");
790+
EXPECT_THAT(Origin("x"), HasLoansTo({"a"}, "p1"));
791+
EXPECT_THAT(Origin("y"), HasLoansTo({"a"}, "p1"));
792+
EXPECT_THAT(Origin("z"), HasLoansTo({"a"}, "p1"));
793+
EXPECT_THAT(Origin("p"), HasLoansTo({"a"}, "p1"));
794+
}
795+
796+
// FIXME: Handle loans in ternary operator!
797+
TEST_F(LifetimeAnalysisTest, GslPointerInConditionalOperator) {
798+
SetupTest(R"(
799+
void target(bool cond) {
800+
MyObj a, b;
801+
View v = cond ? a : b;
802+
POINT(p1);
803+
}
804+
)");
805+
EXPECT_THAT(Origin("v"), HasLoansTo({}, "p1"));
806+
}
807+
808+
// FIXME: Handle temporaries.
809+
TEST_F(LifetimeAnalysisTest, ViewFromTemporary) {
810+
SetupTest(R"(
811+
MyObj temporary();
812+
void target() {
813+
View v = temporary();
814+
POINT(p1);
815+
}
816+
)");
817+
EXPECT_THAT(Origin("v"), HasLoansTo({}, "p1"));
818+
}
819+
820+
TEST_F(LifetimeAnalysisTest, GslPointerWithConstAndAuto) {
821+
SetupTest(R"(
822+
void target() {
823+
MyObj a;
824+
const View v1 = a;
825+
auto v2 = v1;
826+
const auto& v3 = v2;
827+
POINT(p1);
828+
}
829+
)");
830+
EXPECT_THAT(Origin("v1"), HasLoansTo({"a"}, "p1"));
831+
EXPECT_THAT(Origin("v2"), HasLoansTo({"a"}, "p1"));
832+
EXPECT_THAT(Origin("v3"), HasLoansTo({"a"}, "p1"));
833+
}
834+
835+
TEST_F(LifetimeAnalysisTest, GslPointerPropagation) {
836+
SetupTest(R"(
837+
void target() {
838+
MyObj a;
839+
View x = a;
840+
POINT(p1);
841+
842+
View y = x; // Propagation via copy-construction
843+
POINT(p2);
844+
845+
View z;
846+
z = x; // Propagation via copy-assignment
847+
POINT(p3);
848+
}
849+
)");
850+
851+
EXPECT_THAT(Origin("x"), HasLoansTo({"a"}, "p1"));
852+
EXPECT_THAT(Origin("y"), HasLoansTo({"a"}, "p2"));
853+
EXPECT_THAT(Origin("z"), HasLoansTo({"a"}, "p3"));
854+
}
855+
856+
TEST_F(LifetimeAnalysisTest, GslPointerLoanExpiration) {
857+
SetupTest(R"(
858+
void target() {
859+
View x;
860+
{
861+
MyObj a;
862+
x = a;
863+
POINT(before_expiry);
864+
} // `a` is destroyed here.
865+
POINT(after_expiry);
866+
}
867+
)");
868+
869+
EXPECT_THAT(NoLoans(), AreExpiredAt("before_expiry"));
870+
EXPECT_THAT(LoansTo({"a"}), AreExpiredAt("after_expiry"));
871+
}
872+
873+
TEST_F(LifetimeAnalysisTest, GslPointerReassignment) {
874+
SetupTest(R"(
875+
void target() {
876+
MyObj safe;
877+
View v;
878+
v = safe;
879+
POINT(p1);
880+
{
881+
MyObj unsafe;
882+
v = unsafe;
883+
POINT(p2);
884+
} // `unsafe` expires here.
885+
POINT(p3);
886+
}
887+
)");
888+
889+
EXPECT_THAT(Origin("v"), HasLoansTo({"safe"}, "p1"));
890+
EXPECT_THAT(Origin("v"), HasLoansTo({"unsafe"}, "p2"));
891+
EXPECT_THAT(Origin("v"), HasLoansTo({"unsafe"}, "p3")); // The loan is still held, just expired.
892+
EXPECT_THAT(LoansTo({"unsafe"}), AreExpiredAt("p3"));
893+
}
894+
744895
} // anonymous namespace
745896
} // namespace clang::lifetimes::internal

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