[LifetimeSafety] Merge lifetimebound attribute on implicit 'this' across method redeclarations #172146
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@llvm/pr-subscribers-clang Author: Utkarsh Saxena (usx95) ChangesFollowup on #107627 This PR adds support for merging the The implementation adds helper functions to extract the Full diff: https://github.com/llvm/llvm-project/pull/172146.diff 3 Files Affected:
diff --git a/clang/lib/Sema/SemaDecl.cpp b/clang/lib/Sema/SemaDecl.cpp
index 47bd7295e93f6..3dd62c1428271 100644
--- a/clang/lib/Sema/SemaDecl.cpp
+++ b/clang/lib/Sema/SemaDecl.cpp
@@ -4469,6 +4469,52 @@ bool Sema::MergeFunctionDecl(FunctionDecl *New, NamedDecl *&OldD, Scope *S,
return true;
}
+/// Check if a function has a lifetimebound attribute on its function type
+/// (which represents the implicit 'this' parameter for methods).
+/// Returns the attribute if found, nullptr otherwise.
+static const LifetimeBoundAttr *
+getLifetimeBoundAttrFromType(const TypeSourceInfo *TSI) {
+ if (!TSI)
+ return nullptr;
+
+ for (TypeLoc TL = TSI->getTypeLoc();;) {
+ auto ATL = TL.getAsAdjusted<AttributedTypeLoc>();
+ if (!ATL)
+ break;
+ if (auto *LBAttr = ATL.getAttrAs<LifetimeBoundAttr>())
+ return LBAttr;
+ TL = ATL.getModifiedLoc();
+ }
+ return nullptr;
+}
+
+/// Merge lifetimebound attribute on function type (implicit 'this')
+/// from Old to New method declaration.
+static void mergeLifetimeBoundAttrOnMethod(Sema &S, CXXMethodDecl *New,
+ const CXXMethodDecl *Old) {
+ const TypeSourceInfo *OldTSI = Old->getTypeSourceInfo();
+ const TypeSourceInfo *NewTSI = New->getTypeSourceInfo();
+
+ if (!OldTSI || !NewTSI)
+ return;
+
+ const LifetimeBoundAttr *OldLBAttr = getLifetimeBoundAttrFromType(OldTSI);
+ const LifetimeBoundAttr *NewLBAttr = getLifetimeBoundAttrFromType(NewTSI);
+
+ // If Old has lifetimebound but New doesn't, add it to New
+ if (OldLBAttr && !NewLBAttr) {
+ QualType NewMethodType = New->getType();
+ QualType AttributedType =
+ S.Context.getAttributedType(OldLBAttr, NewMethodType, NewMethodType);
+ TypeLocBuilder TLB;
+ TLB.pushFullCopy(NewTSI->getTypeLoc());
+ AttributedTypeLoc TyLoc = TLB.push<AttributedTypeLoc>(AttributedType);
+ TyLoc.setAttr(OldLBAttr);
+ New->setType(AttributedType);
+ New->setTypeSourceInfo(TLB.getTypeSourceInfo(S.Context, AttributedType));
+ }
+}
+
bool Sema::MergeCompatibleFunctionDecls(FunctionDecl *New, FunctionDecl *Old,
Scope *S, bool MergeTypeWithOld) {
// Merge the attributes
@@ -4485,12 +4531,17 @@ bool Sema::MergeCompatibleFunctionDecls(FunctionDecl *New, FunctionDecl *Old,
// Merge attributes from the parameters. These can mismatch with K&R
// declarations.
if (New->getNumParams() == Old->getNumParams())
- for (unsigned i = 0, e = New->getNumParams(); i != e; ++i) {
- ParmVarDecl *NewParam = New->getParamDecl(i);
- ParmVarDecl *OldParam = Old->getParamDecl(i);
- mergeParamDeclAttributes(NewParam, OldParam, *this);
- mergeParamDeclTypes(NewParam, OldParam, *this);
- }
+ for (unsigned i = 0, e = New->getNumParams(); i != e; ++i) {
+ ParmVarDecl *NewParam = New->getParamDecl(i);
+ ParmVarDecl *OldParam = Old->getParamDecl(i);
+ mergeParamDeclAttributes(NewParam, OldParam, *this);
+ mergeParamDeclTypes(NewParam, OldParam, *this);
+ }
+
+ // Merge function type attributes (e.g., lifetimebound on implicit 'this').
+ if (auto *NewMethod = dyn_cast<CXXMethodDecl>(New))
+ if (auto *OldMethod = dyn_cast<CXXMethodDecl>(Old))
+ mergeLifetimeBoundAttrOnMethod(*this, NewMethod, OldMethod);
if (getLangOpts().CPlusPlus)
return MergeCXXFunctionDecl(New, Old, S);
diff --git a/clang/test/Sema/warn-lifetime-safety.cpp b/clang/test/Sema/warn-lifetime-safety.cpp
index 1191469e23df1..658d68db44369 100644
--- a/clang/test/Sema/warn-lifetime-safety.cpp
+++ b/clang/test/Sema/warn-lifetime-safety.cpp
@@ -943,3 +943,25 @@ void parentheses(bool cond) {
} // expected-note 4 {{destroyed here}}
(void)*p; // expected-note 4 {{later used here}}
}
+
+// Implicit this annotations with redecls.
+namespace GH172013 {
+// https://github.com/llvm/llvm-project/issues/62072
+// https://github.com/llvm/llvm-project/issues/172013
+struct S {
+ View x() const [[clang::lifetimebound]];
+ MyObj i;
+};
+
+View S::x() const { return i; }
+
+void bar() {
+ View x;
+ {
+ S s;
+ x = s.x(); // expected-warning {{object whose reference is captured does not live long enough}}
+ View y = S().x(); // FIXME: Handle temporaries.
+ } // expected-note {{destroyed here}}
+ (void)x; // expected-note {{used here}}
+}
+}
diff --git a/clang/test/SemaCXX/attr-lifetimebound.cpp b/clang/test/SemaCXX/attr-lifetimebound.cpp
index 111bad65f7e1b..5b0aa0e518cb3 100644
--- a/clang/test/SemaCXX/attr-lifetimebound.cpp
+++ b/clang/test/SemaCXX/attr-lifetimebound.cpp
@@ -75,6 +75,18 @@ namespace usage_ok {
r = A(1); // expected-warning {{object backing the pointer 'r' will be destroyed at the end of the full-expression}}
}
+ // Test that lifetimebound on implicit 'this' is propagated across redeclarations
+ struct B {
+ int *method() [[clang::lifetimebound]];
+ int i;
+ };
+ int *B::method() { return &i; }
+
+ void test_lifetimebound_on_implicit_this() {
+ int *t = B().method(); // expected-warning {{temporary whose address is used as value of local variable 't' will be destroyed at the end of the full-expression}}
+ t = {B().method()}; // expected-warning {{object backing the pointer 't' will be destroyed at the end of the full-expression}}
+ }
+
struct FieldCheck {
struct Set {
int a;
|
Member
|
@llvm/pr-subscribers-clang-temporal-safety Author: Utkarsh Saxena (usx95) ChangesFollowup on #107627 This PR adds support for merging the The implementation adds helper functions to extract the Full diff: https://github.com/llvm/llvm-project/pull/172146.diff 3 Files Affected:
diff --git a/clang/lib/Sema/SemaDecl.cpp b/clang/lib/Sema/SemaDecl.cpp
index 47bd7295e93f6..3dd62c1428271 100644
--- a/clang/lib/Sema/SemaDecl.cpp
+++ b/clang/lib/Sema/SemaDecl.cpp
@@ -4469,6 +4469,52 @@ bool Sema::MergeFunctionDecl(FunctionDecl *New, NamedDecl *&OldD, Scope *S,
return true;
}
+/// Check if a function has a lifetimebound attribute on its function type
+/// (which represents the implicit 'this' parameter for methods).
+/// Returns the attribute if found, nullptr otherwise.
+static const LifetimeBoundAttr *
+getLifetimeBoundAttrFromType(const TypeSourceInfo *TSI) {
+ if (!TSI)
+ return nullptr;
+
+ for (TypeLoc TL = TSI->getTypeLoc();;) {
+ auto ATL = TL.getAsAdjusted<AttributedTypeLoc>();
+ if (!ATL)
+ break;
+ if (auto *LBAttr = ATL.getAttrAs<LifetimeBoundAttr>())
+ return LBAttr;
+ TL = ATL.getModifiedLoc();
+ }
+ return nullptr;
+}
+
+/// Merge lifetimebound attribute on function type (implicit 'this')
+/// from Old to New method declaration.
+static void mergeLifetimeBoundAttrOnMethod(Sema &S, CXXMethodDecl *New,
+ const CXXMethodDecl *Old) {
+ const TypeSourceInfo *OldTSI = Old->getTypeSourceInfo();
+ const TypeSourceInfo *NewTSI = New->getTypeSourceInfo();
+
+ if (!OldTSI || !NewTSI)
+ return;
+
+ const LifetimeBoundAttr *OldLBAttr = getLifetimeBoundAttrFromType(OldTSI);
+ const LifetimeBoundAttr *NewLBAttr = getLifetimeBoundAttrFromType(NewTSI);
+
+ // If Old has lifetimebound but New doesn't, add it to New
+ if (OldLBAttr && !NewLBAttr) {
+ QualType NewMethodType = New->getType();
+ QualType AttributedType =
+ S.Context.getAttributedType(OldLBAttr, NewMethodType, NewMethodType);
+ TypeLocBuilder TLB;
+ TLB.pushFullCopy(NewTSI->getTypeLoc());
+ AttributedTypeLoc TyLoc = TLB.push<AttributedTypeLoc>(AttributedType);
+ TyLoc.setAttr(OldLBAttr);
+ New->setType(AttributedType);
+ New->setTypeSourceInfo(TLB.getTypeSourceInfo(S.Context, AttributedType));
+ }
+}
+
bool Sema::MergeCompatibleFunctionDecls(FunctionDecl *New, FunctionDecl *Old,
Scope *S, bool MergeTypeWithOld) {
// Merge the attributes
@@ -4485,12 +4531,17 @@ bool Sema::MergeCompatibleFunctionDecls(FunctionDecl *New, FunctionDecl *Old,
// Merge attributes from the parameters. These can mismatch with K&R
// declarations.
if (New->getNumParams() == Old->getNumParams())
- for (unsigned i = 0, e = New->getNumParams(); i != e; ++i) {
- ParmVarDecl *NewParam = New->getParamDecl(i);
- ParmVarDecl *OldParam = Old->getParamDecl(i);
- mergeParamDeclAttributes(NewParam, OldParam, *this);
- mergeParamDeclTypes(NewParam, OldParam, *this);
- }
+ for (unsigned i = 0, e = New->getNumParams(); i != e; ++i) {
+ ParmVarDecl *NewParam = New->getParamDecl(i);
+ ParmVarDecl *OldParam = Old->getParamDecl(i);
+ mergeParamDeclAttributes(NewParam, OldParam, *this);
+ mergeParamDeclTypes(NewParam, OldParam, *this);
+ }
+
+ // Merge function type attributes (e.g., lifetimebound on implicit 'this').
+ if (auto *NewMethod = dyn_cast<CXXMethodDecl>(New))
+ if (auto *OldMethod = dyn_cast<CXXMethodDecl>(Old))
+ mergeLifetimeBoundAttrOnMethod(*this, NewMethod, OldMethod);
if (getLangOpts().CPlusPlus)
return MergeCXXFunctionDecl(New, Old, S);
diff --git a/clang/test/Sema/warn-lifetime-safety.cpp b/clang/test/Sema/warn-lifetime-safety.cpp
index 1191469e23df1..658d68db44369 100644
--- a/clang/test/Sema/warn-lifetime-safety.cpp
+++ b/clang/test/Sema/warn-lifetime-safety.cpp
@@ -943,3 +943,25 @@ void parentheses(bool cond) {
} // expected-note 4 {{destroyed here}}
(void)*p; // expected-note 4 {{later used here}}
}
+
+// Implicit this annotations with redecls.
+namespace GH172013 {
+// https://github.com/llvm/llvm-project/issues/62072
+// https://github.com/llvm/llvm-project/issues/172013
+struct S {
+ View x() const [[clang::lifetimebound]];
+ MyObj i;
+};
+
+View S::x() const { return i; }
+
+void bar() {
+ View x;
+ {
+ S s;
+ x = s.x(); // expected-warning {{object whose reference is captured does not live long enough}}
+ View y = S().x(); // FIXME: Handle temporaries.
+ } // expected-note {{destroyed here}}
+ (void)x; // expected-note {{used here}}
+}
+}
diff --git a/clang/test/SemaCXX/attr-lifetimebound.cpp b/clang/test/SemaCXX/attr-lifetimebound.cpp
index 111bad65f7e1b..5b0aa0e518cb3 100644
--- a/clang/test/SemaCXX/attr-lifetimebound.cpp
+++ b/clang/test/SemaCXX/attr-lifetimebound.cpp
@@ -75,6 +75,18 @@ namespace usage_ok {
r = A(1); // expected-warning {{object backing the pointer 'r' will be destroyed at the end of the full-expression}}
}
+ // Test that lifetimebound on implicit 'this' is propagated across redeclarations
+ struct B {
+ int *method() [[clang::lifetimebound]];
+ int i;
+ };
+ int *B::method() { return &i; }
+
+ void test_lifetimebound_on_implicit_this() {
+ int *t = B().method(); // expected-warning {{temporary whose address is used as value of local variable 't' will be destroyed at the end of the full-expression}}
+ t = {B().method()}; // expected-warning {{object backing the pointer 't' will be destroyed at the end of the full-expression}}
+ }
+
struct FieldCheck {
struct Set {
int a;
|
cor3ntin
reviewed
Dec 13, 2025
Comment on lines
+4505
to
+4517
| if (OldLBAttr && !NewLBAttr) { | ||
| QualType NewMethodType = New->getType(); | ||
| QualType AttributedType = | ||
| S.Context.getAttributedType(OldLBAttr, NewMethodType, NewMethodType); | ||
| TypeLocBuilder TLB; | ||
| TLB.pushFullCopy(NewTSI->getTypeLoc()); | ||
| AttributedTypeLoc TyLoc = TLB.push<AttributedTypeLoc>(AttributedType); | ||
| TyLoc.setAttr(OldLBAttr); | ||
| New->setType(AttributedType); | ||
| New->setTypeSourceInfo(TLB.getTypeSourceInfo(S.Context, AttributedType)); | ||
| } | ||
| } |
Contributor
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What about the opposite scenario?
Contributor
Author
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The idea is to read mostRecentDecl for analysis and it would reflect all the merged attributes seen until now.
cor3ntin
reviewed
Dec 13, 2025
clang/lib/Sema/SemaDecl.cpp
Outdated
Comment on lines
4480
to
4487
| for (TypeLoc TL = TSI->getTypeLoc();;) { | ||
| auto ATL = TL.getAsAdjusted<AttributedTypeLoc>(); | ||
| if (!ATL) | ||
| break; | ||
| if (auto *LBAttr = ATL.getAttrAs<LifetimeBoundAttr>()) | ||
| return LBAttr; | ||
| TL = ATL.getModifiedLoc(); | ||
| } |
Contributor
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This might be a bit too clever - I'd prefer a while(true) with a comment
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Followup on #107627
Fixes #62072
Fixes #172013
This PR adds support for merging the
lifetimeboundattribute on the implicitthisparameter when merging method declarations. Previously, if a method was declared withlifetimeboundon its function type (which represents the implicitthisparameter), this attribute would not be propagated to the method definition, causing lifetime safety warnings to be missed.The implementation adds helper functions to extract the
lifetimeboundattribute from a function type and to merge this attribute from an old method declaration to a new one when appropriate.