[llvm-branch-commits] [clang] [LifetimeSafety] Add support for GSL Pointer types (PR #154009)
Utkarsh Saxena via llvm-branch-commits
llvm-branch-commits at lists.llvm.org
Tue Aug 19 07:29:33 PDT 2025
https://github.com/usx95 updated https://github.com/llvm/llvm-project/pull/154009
>From fa5312a0ce65a37d25a9eba9cb6042116126195d Mon Sep 17 00:00:00 2001
From: Utkarsh Saxena <usx at google.com>
Date: Sun, 17 Aug 2025 10:10:18 +0000
Subject: [PATCH] [LifetimeSafety] Track gsl::Pointer types
---
clang/lib/Analysis/LifetimeSafety.cpp | 128 +++++++++++++-
clang/test/Sema/warn-lifetime-safety.cpp | 120 +++++++++++--
.../unittests/Analysis/LifetimeSafetyTest.cpp | 157 +++++++++++++++++-
3 files changed, 386 insertions(+), 19 deletions(-)
diff --git a/clang/lib/Analysis/LifetimeSafety.cpp b/clang/lib/Analysis/LifetimeSafety.cpp
index 00efa4c5e548f..f9afa3ff6b5d9 100644
--- a/clang/lib/Analysis/LifetimeSafety.cpp
+++ b/clang/lib/Analysis/LifetimeSafety.cpp
@@ -433,6 +433,31 @@ class FactGeneratorVisitor : public ConstStmtVisitor<FactGeneratorVisitor> {
void VisitDeclRefExpr(const DeclRefExpr *DRE) { handleUse(DRE); }
+ void VisitCXXConstructExpr(const CXXConstructExpr *CCE) {
+ if (!isGslPointerType(CCE->getType()))
+ return;
+
+ if (CCE->getNumArgs() > 0 && hasOrigin(CCE->getArg(0)->getType()))
+ // This is a propagation.
+ addAssignOriginFact(*CCE, *CCE->getArg(0));
+ else
+ // This could be a new borrow.
+ checkForBorrows(CCE, CCE->getConstructor(),
+ {CCE->getArgs(), CCE->getNumArgs()});
+ }
+
+ void VisitCXXMemberCallExpr(const CXXMemberCallExpr *MCE) {
+ if (!isGslPointerType(MCE->getImplicitObjectArgument()->getType()))
+ return;
+ // Specifically for conversion operators, like `std::string_view p = a;`
+ if (isa<CXXConversionDecl>(MCE->getCalleeDecl())) {
+ // The argument is the implicit object itself.
+ checkForBorrows(MCE, MCE->getMethodDecl(),
+ {MCE->getImplicitObjectArgument()});
+ }
+ // Note: A more general VisitCallExpr could also be used here.
+ }
+
void VisitCXXNullPtrLiteralExpr(const CXXNullPtrLiteralExpr *N) {
/// TODO: Handle nullptr expr as a special 'null' loan. Uninitialized
/// pointers can use the same type of loan.
@@ -492,10 +517,27 @@ class FactGeneratorVisitor : public ConstStmtVisitor<FactGeneratorVisitor> {
void VisitCXXFunctionalCastExpr(const CXXFunctionalCastExpr *FCE) {
// Check if this is a test point marker. If so, we are done with this
// expression.
- if (VisitTestPoint(FCE))
+ if (handleTestPoint(FCE))
return;
- // Visit as normal otherwise.
- Base::VisitCXXFunctionalCastExpr(FCE);
+ if (isGslPointerType(FCE->getType()))
+ addAssignOriginFact(*FCE, *FCE->getSubExpr());
+ }
+
+ void VisitInitListExpr(const InitListExpr *ILE) {
+ if (!hasOrigin(ILE->getType()))
+ return;
+ // For list initialization with a single element, like `View{...}`, the
+ // origin of the list itself is the origin of its single element.
+ if (ILE->getNumInits() == 1)
+ addAssignOriginFact(*ILE, *ILE->getInit(0));
+ }
+
+ void VisitMaterializeTemporaryExpr(const MaterializeTemporaryExpr *MTE) {
+ if (!hasOrigin(MTE->getType()))
+ return;
+ // A temporary object's origin is the same as the origin of the
+ // expression that initializes it.
+ addAssignOriginFact(*MTE, *MTE->getSubExpr());
}
void handleDestructor(const CFGAutomaticObjDtor &DtorOpt) {
@@ -521,8 +563,75 @@ class FactGeneratorVisitor : public ConstStmtVisitor<FactGeneratorVisitor> {
}
private:
+ static bool isGslPointerType(QualType QT) {
+ if (const auto *RD = QT->getAsCXXRecordDecl()) {
+ // We need to check the template definition for specializations.
+ if (auto *CTSD = dyn_cast<ClassTemplateSpecializationDecl>(RD))
+ return CTSD->getSpecializedTemplate()
+ ->getTemplatedDecl()
+ ->hasAttr<PointerAttr>();
+ return RD->hasAttr<PointerAttr>();
+ }
+ return false;
+ }
+
// Check if a type has an origin.
- bool hasOrigin(QualType QT) { return QT->isPointerOrReferenceType(); }
+ static bool hasOrigin(QualType QT) {
+ if (QT->isFunctionPointerType())
+ return false;
+ return QT->isPointerOrReferenceType() || isGslPointerType(QT);
+ }
+
+ /// Checks if a call-like expression creates a borrow by passing a local
+ /// value to a reference parameter, creating an IssueFact if it does.
+ void checkForBorrows(const Expr *Call, const FunctionDecl *FD,
+ ArrayRef<const Expr *> Args) {
+ if (!FD)
+ return;
+
+ for (unsigned I = 0; I < Args.size(); ++I) {
+ if (I >= FD->getNumParams())
+ break;
+
+ const ParmVarDecl *Param = FD->getParamDecl(I);
+ const Expr *Arg = Args[I];
+
+ // This is the core condition for a new borrow: a value type (no origin)
+ // is passed to a reference parameter.
+ if (Param->getType()->isReferenceType() && !hasOrigin(Arg->getType())) {
+ if (const Loan *L = createLoanFrom(Arg, Call)) {
+ OriginID OID = FactMgr.getOriginMgr().getOrCreate(*Call);
+ CurrentBlockFacts.push_back(
+ FactMgr.createFact<IssueFact>(L->ID, OID));
+ // For view creation, we assume the first borrow is the significant
+ // one.
+ return;
+ }
+ }
+ }
+ }
+
+ /// Attempts to create a loan by analyzing the source expression of a borrow.
+ /// This method is the single point for creating loans, allowing for future
+ /// expansion to handle temporaries, field members, etc.
+ /// \param SourceExpr The expression representing the object being borrowed
+ /// from.
+ /// \param IssueExpr The expression that triggers the borrow (e.g., a
+ /// constructor call).
+ /// \return The new Loan on success, nullptr on failure.
+ const Loan *createLoanFrom(const Expr *SourceExpr, const Expr *IssueExpr) {
+ // For now, we only handle direct borrows from local variables.
+ // In the future, this can be extended to handle MaterializeTemporaryExpr,
+ // etc.
+ if (const auto *DRE =
+ dyn_cast<DeclRefExpr>(SourceExpr->IgnoreParenImpCasts())) {
+ if (const auto *VD = dyn_cast<ValueDecl>(DRE->getDecl())) {
+ AccessPath Path(VD);
+ return &FactMgr.getLoanMgr().addLoan(Path, IssueExpr);
+ }
+ }
+ return nullptr;
+ }
template <typename Destination, typename Source>
void addAssignOriginFact(const Destination &D, const Source &S) {
@@ -534,7 +643,7 @@ class FactGeneratorVisitor : public ConstStmtVisitor<FactGeneratorVisitor> {
/// Checks if the expression is a `void("__lifetime_test_point_...")` cast.
/// If so, creates a `TestPointFact` and returns true.
- bool VisitTestPoint(const CXXFunctionalCastExpr *FCE) {
+ bool handleTestPoint(const CXXFunctionalCastExpr *FCE) {
if (!FCE->getType()->isVoidType())
return false;
@@ -612,10 +721,13 @@ class FactGenerator : public RecursiveASTVisitor<FactGenerator> {
for (const CFGBlock *Block : *AC.getAnalysis<PostOrderCFGView>()) {
FactGeneratorBlockRAII BlockGenerator(FG, Block);
for (const CFGElement &Element : *Block) {
- if (std::optional<CFGStmt> CS = Element.getAs<CFGStmt>())
+ if (std::optional<CFGStmt> CS = Element.getAs<CFGStmt>()) {
+ DEBUG_WITH_TYPE("PrintCFG", llvm::dbgs() << " ================== \n");
+ DEBUG_WITH_TYPE("PrintCFG", CS->dump());
+ DEBUG_WITH_TYPE("PrintCFG", CS->getStmt()->dumpColor());
TraverseStmt(const_cast<Stmt *>(CS->getStmt()));
- else if (std::optional<CFGAutomaticObjDtor> DtorOpt =
- Element.getAs<CFGAutomaticObjDtor>())
+ } else if (std::optional<CFGAutomaticObjDtor> DtorOpt =
+ Element.getAs<CFGAutomaticObjDtor>())
FG.handleDestructor(*DtorOpt);
}
}
diff --git a/clang/test/Sema/warn-lifetime-safety.cpp b/clang/test/Sema/warn-lifetime-safety.cpp
index 660b9c9d5e243..bc8a5f3f7150f 100644
--- a/clang/test/Sema/warn-lifetime-safety.cpp
+++ b/clang/test/Sema/warn-lifetime-safety.cpp
@@ -6,6 +6,12 @@ struct MyObj {
MyObj operator+(MyObj);
};
+struct [[gsl::Pointer()]] View {
+ View(const MyObj&); // Borrows from MyObj
+ View();
+ void use() const;
+};
+
//===----------------------------------------------------------------------===//
// Basic Definite Use-After-Free (-W...permissive)
// These are cases where the pointer is guaranteed to be dangling at the use site.
@@ -20,12 +26,31 @@ void definite_simple_case() {
(void)*p; // expected-note {{later used here}}
}
+void definite_simple_case_gsl() {
+ View v;
+ {
+ MyObj s;
+ v = s; // expected-warning {{object whose reference is captured does not live long enough}}
+ } // expected-note {{destroyed here}}
+ v.use(); // expected-note {{later used here}}
+}
+
void no_use_no_error() {
MyObj* p;
{
MyObj s;
p = &s;
}
+ // 'p' is dangling here, but since it is never used, no warning is issued.
+}
+
+void no_use_no_error_gsl() {
+ View v;
+ {
+ MyObj s;
+ v = s;
+ }
+ // 'v' is dangling here, but since it is never used, no warning is issued.
}
void definite_pointer_chain() {
@@ -39,6 +64,16 @@ void definite_pointer_chain() {
(void)*q; // expected-note {{later used here}}
}
+void definite_propagation_gsl() {
+ View v1, v2;
+ {
+ MyObj s;
+ v1 = s; // expected-warning {{object whose reference is captured does not live long enough}}
+ v2 = v1;
+ } // expected-note {{destroyed here}}
+ v2.use(); // expected-note {{later used here}}
+}
+
void definite_multiple_uses_one_warning() {
MyObj* p;
{
@@ -78,6 +113,19 @@ void definite_single_pointer_multiple_loans(bool cond) {
(void)*p; // expected-note 2 {{later used here}}
}
+void definite_single_pointer_multiple_loans_gsl(bool cond) {
+ View v;
+ if (cond){
+ MyObj s;
+ v = s; // expected-warning {{object whose reference is captured does not live long enough}}
+ } // expected-note {{destroyed here}}
+ else {
+ MyObj t;
+ v = t; // expected-warning {{object whose reference is captured does not live long enough}}
+ } // expected-note {{destroyed here}}
+ v.use(); // expected-note 2 {{later used here}}
+}
+
//===----------------------------------------------------------------------===//
// Potential (Maybe) Use-After-Free (-W...strict)
@@ -94,18 +142,14 @@ void potential_if_branch(bool cond) {
(void)*p; // expected-note {{later used here}}
}
-// If all paths lead to a dangle, it becomes a definite error.
-void potential_becomes_definite(bool cond) {
- MyObj* p;
+void potential_if_branch_gsl(bool cond) {
+ MyObj safe;
+ View v = safe;
if (cond) {
- MyObj temp1;
- p = &temp1; // expected-warning {{does not live long enough}}
- } // expected-note {{destroyed here}}
- else {
- MyObj temp2;
- p = &temp2; // expected-warning {{does not live long enough}}
+ MyObj temp;
+ v = temp; // expected-warning {{object whose reference is captured may not live long enough}}
} // expected-note {{destroyed here}}
- (void)*p; // expected-note 2 {{later used here}}
+ v.use(); // expected-note {{later used here}}
}
void definite_potential_together(bool cond) {
@@ -159,6 +203,16 @@ void potential_for_loop_use_after_loop_body(MyObj safe) {
(void)*p; // expected-note {{later used here}}
}
+void potential_for_loop_gsl() {
+ MyObj safe;
+ View v = safe;
+ for (int i = 0; i < 1; ++i) {
+ MyObj s;
+ v = s; // expected-warning {{object whose reference is captured may not live long enough}}
+ } // expected-note {{destroyed here}}
+ v.use(); // expected-note {{later used here}}
+}
+
void potential_for_loop_use_before_loop_body(MyObj safe) {
MyObj* p = &safe;
for (int i = 0; i < 1; ++i) {
@@ -182,6 +236,19 @@ void potential_loop_with_break(bool cond) {
(void)*p; // expected-note {{later used here}}
}
+void potential_loop_with_break_gsl(bool cond) {
+ MyObj safe;
+ View v = safe;
+ for (int i = 0; i < 10; ++i) {
+ if (cond) {
+ MyObj temp;
+ v = temp; // expected-warning {{object whose reference is captured may not live long enough}}
+ break; // expected-note {{destroyed here}}
+ }
+ }
+ v.use(); // expected-note {{later used here}}
+}
+
void potential_multiple_expiry_of_same_loan(bool cond) {
// Choose the last expiry location for the loan.
MyObj safe;
@@ -258,6 +325,28 @@ void definite_switch(int mode) {
(void)*p; // expected-note 3 {{later used here}}
}
+void definite_switch_gsl(int mode) {
+ View v;
+ switch (mode) {
+ case 1: {
+ MyObj temp1;
+ v = temp1; // expected-warning {{object whose reference is captured does not live long enough}}
+ break; // expected-note {{destroyed here}}
+ }
+ case 2: {
+ MyObj temp2;
+ v = temp2; // expected-warning {{object whose reference is captured does not live long enough}}
+ break; // expected-note {{destroyed here}}
+ }
+ default: {
+ MyObj temp3;
+ v = temp3; // expected-warning {{object whose reference is captured does not live long enough}}
+ break; // expected-note {{destroyed here}}
+ }
+ }
+ v.use(); // expected-note 3 {{later used here}}
+}
+
//===----------------------------------------------------------------------===//
// No-Error Cases
//===----------------------------------------------------------------------===//
@@ -271,3 +360,14 @@ void no_error_if_dangle_then_rescue() {
p = &safe; // p is "rescued" before use.
(void)*p; // This is safe.
}
+
+void no_error_if_dangle_then_rescue_gsl() {
+ MyObj safe;
+ View v;
+ {
+ MyObj temp;
+ v = temp; // 'v' is temporarily dangling.
+ }
+ v = safe; // 'v' is "rescued" before use by reassigning to a valid object.
+ v.use(); // This is safe.
+}
diff --git a/clang/unittests/Analysis/LifetimeSafetyTest.cpp b/clang/unittests/Analysis/LifetimeSafetyTest.cpp
index 13e5832d70050..98862a1a157b8 100644
--- a/clang/unittests/Analysis/LifetimeSafetyTest.cpp
+++ b/clang/unittests/Analysis/LifetimeSafetyTest.cpp
@@ -11,7 +11,6 @@
#include "clang/ASTMatchers/ASTMatchers.h"
#include "clang/Testing/TestAST.h"
#include "llvm/ADT/StringMap.h"
-#include "llvm/Testing/Support/Error.h"
#include "gmock/gmock.h"
#include "gtest/gtest.h"
#include <optional>
@@ -31,7 +30,13 @@ class LifetimeTestRunner {
LifetimeTestRunner(llvm::StringRef Code) {
std::string FullCode = R"(
#define POINT(name) void("__lifetime_test_point_" #name)
+
struct MyObj { ~MyObj() {} int i; };
+
+ struct [[gsl::Pointer()]] View {
+ View(const MyObj&);
+ View();
+ };
)";
FullCode += Code.str();
@@ -741,5 +746,155 @@ TEST_F(LifetimeAnalysisTest, NoDuplicateLoansForImplicitCastToConst) {
EXPECT_THAT(Helper->getLoansForVar("a"), SizeIs(2));
}
+TEST_F(LifetimeAnalysisTest, GslPointerSimpleLoan) {
+ SetupTest(R"(
+ void target() {
+ MyObj a;
+ View x = a;
+ POINT(p1);
+ }
+ )");
+ EXPECT_THAT(Origin("x"), HasLoansTo({"a"}, "p1"));
+}
+
+TEST_F(LifetimeAnalysisTest, GslPointerConstructFromOwner) {
+ SetupTest(R"(
+ void target() {
+ MyObj al, bl, cl, dl, el, fl;
+ View a = View(al);
+ View b = View{bl};
+ View c = View(View(View(cl)));
+ View d = View{View(View(dl))};
+ View e = View{View{View{el}}};
+ View f = {fl};
+ POINT(p1);
+ }
+ )");
+ EXPECT_THAT(Origin("a"), HasLoansTo({"al"}, "p1"));
+ EXPECT_THAT(Origin("b"), HasLoansTo({"bl"}, "p1"));
+ EXPECT_THAT(Origin("c"), HasLoansTo({"cl"}, "p1"));
+ EXPECT_THAT(Origin("d"), HasLoansTo({"dl"}, "p1"));
+ EXPECT_THAT(Origin("e"), HasLoansTo({"el"}, "p1"));
+ EXPECT_THAT(Origin("f"), HasLoansTo({"fl"}, "p1"));
+}
+
+TEST_F(LifetimeAnalysisTest, GslPointerConstructFromView) {
+ SetupTest(R"(
+ void target() {
+ MyObj a;
+ View x = View(a);
+ View y = View{x};
+ View z = View(View(View(y)));
+ View p = View{View(View(x))};
+ View q = {x};
+ POINT(p1);
+ }
+ )");
+ EXPECT_THAT(Origin("x"), HasLoansTo({"a"}, "p1"));
+ EXPECT_THAT(Origin("y"), HasLoansTo({"a"}, "p1"));
+ EXPECT_THAT(Origin("z"), HasLoansTo({"a"}, "p1"));
+ EXPECT_THAT(Origin("p"), HasLoansTo({"a"}, "p1"));
+ EXPECT_THAT(Origin("q"), HasLoansTo({"a"}, "p1"));
+}
+
+// FIXME: Handle loans in ternary operator!
+TEST_F(LifetimeAnalysisTest, GslPointerInConditionalOperator) {
+ SetupTest(R"(
+ void target(bool cond) {
+ MyObj a, b;
+ View v = cond ? a : b;
+ POINT(p1);
+ }
+ )");
+ EXPECT_THAT(Origin("v"), HasLoansTo({}, "p1"));
+}
+
+// FIXME: Handle temporaries.
+TEST_F(LifetimeAnalysisTest, ViewFromTemporary) {
+ SetupTest(R"(
+ MyObj temporary();
+ void target() {
+ View v = temporary();
+ POINT(p1);
+ }
+ )");
+ EXPECT_THAT(Origin("v"), HasLoansTo({}, "p1"));
+}
+
+TEST_F(LifetimeAnalysisTest, GslPointerWithConstAndAuto) {
+ SetupTest(R"(
+ void target() {
+ MyObj a;
+ const View v1 = a;
+ auto v2 = v1;
+ const auto& v3 = v2;
+ POINT(p1);
+ }
+ )");
+ EXPECT_THAT(Origin("v1"), HasLoansTo({"a"}, "p1"));
+ EXPECT_THAT(Origin("v2"), HasLoansTo({"a"}, "p1"));
+ EXPECT_THAT(Origin("v3"), HasLoansTo({"a"}, "p1"));
+}
+
+TEST_F(LifetimeAnalysisTest, GslPointerPropagation) {
+ SetupTest(R"(
+ void target() {
+ MyObj a;
+ View x = a;
+ POINT(p1);
+
+ View y = x; // Propagation via copy-construction
+ POINT(p2);
+
+ View z;
+ z = x; // Propagation via copy-assignment
+ POINT(p3);
+ }
+ )");
+
+ EXPECT_THAT(Origin("x"), HasLoansTo({"a"}, "p1"));
+ EXPECT_THAT(Origin("y"), HasLoansTo({"a"}, "p2"));
+ EXPECT_THAT(Origin("z"), HasLoansTo({"a"}, "p3"));
+}
+
+TEST_F(LifetimeAnalysisTest, GslPointerLoanExpiration) {
+ SetupTest(R"(
+ void target() {
+ View x;
+ {
+ MyObj a;
+ x = a;
+ POINT(before_expiry);
+ } // `a` is destroyed here.
+ POINT(after_expiry);
+ }
+ )");
+
+ EXPECT_THAT(NoLoans(), AreExpiredAt("before_expiry"));
+ EXPECT_THAT(LoansTo({"a"}), AreExpiredAt("after_expiry"));
+}
+
+TEST_F(LifetimeAnalysisTest, GslPointerReassignment) {
+ SetupTest(R"(
+ void target() {
+ MyObj safe;
+ View v;
+ v = safe;
+ POINT(p1);
+ {
+ MyObj unsafe;
+ v = unsafe;
+ POINT(p2);
+ } // `unsafe` expires here.
+ POINT(p3);
+ }
+ )");
+
+ EXPECT_THAT(Origin("v"), HasLoansTo({"safe"}, "p1"));
+ EXPECT_THAT(Origin("v"), HasLoansTo({"unsafe"}, "p2"));
+ EXPECT_THAT(Origin("v"), HasLoansTo({"unsafe"}, "p3"));
+ EXPECT_THAT(LoansTo({"unsafe"}), AreExpiredAt("p3"));
+}
+
} // anonymous namespace
} // namespace clang::lifetimes::internal
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