https://github.com/Sirraide updated
https://github.com/llvm/llvm-project/pull/154276
>From cd2b97cdd9d6cc3f575d71cee24c8f42f57bdb6a Mon Sep 17 00:00:00 2001
From: Sirraide <aeternalm...@gmail.com>
Date: Tue, 19 Aug 2025 08:57:23 +0200
Subject: [PATCH 1/3] [Clang] [Sema] Always rebuild 'this' captured by value in
a lambda with a dependent explicit object parameter
---
clang/docs/ReleaseNotes.rst | 2 ++
clang/lib/Sema/TreeTransform.h | 7 ++++--
clang/test/CodeGenCXX/cxx2b-deducing-this.cpp | 25 +++++++++++++++++++
3 files changed, 32 insertions(+), 2 deletions(-)
diff --git a/clang/docs/ReleaseNotes.rst b/clang/docs/ReleaseNotes.rst
index b86a9c437ffb1..7eccd6f4d2b92 100644
--- a/clang/docs/ReleaseNotes.rst
+++ b/clang/docs/ReleaseNotes.rst
@@ -234,6 +234,8 @@ Bug Fixes to C++ Support
"intializing multiple members of union" coincide (#GH149985).
- Fix a crash when using ``explicit(bool)`` in pre-C++11 language modes.
(#GH152729)
- Fix the parsing of variadic member functions when the ellipis immediately
follows a default argument.(#GH153445)
+- Fixed a bug that caused ``this`` captured by value in a lambda with a
dependent explicit object parameter to not be
+ instantiated properly. (#GH154054)
Bug Fixes to AST Handling
^^^^^^^^^^^^^^^^^^^^^^^^^
diff --git a/clang/lib/Sema/TreeTransform.h b/clang/lib/Sema/TreeTransform.h
index 055d3cd1a8609..485b1fa6f6875 100644
--- a/clang/lib/Sema/TreeTransform.h
+++ b/clang/lib/Sema/TreeTransform.h
@@ -14307,7 +14307,9 @@
TreeTransform<Derived>::TransformCXXThisExpr(CXXThisExpr *E) {
// for type deduction, so we need to recompute it.
//
// Always recompute the type if we're in the body of a lambda, and
- // 'this' is dependent on a lambda's explicit object parameter.
+ // 'this' is dependent on a lambda's explicit object parameter; we
+ // also need to always rebuild the expression in this case to clear
+ // the flag.
QualType T = [&]() {
auto &S = getSema();
if (E->isCapturedByCopyInLambdaWithExplicitObjectParameter())
@@ -14317,7 +14319,8 @@
TreeTransform<Derived>::TransformCXXThisExpr(CXXThisExpr *E) {
return S.getCurrentThisType();
}();
- if (!getDerived().AlwaysRebuild() && T == E->getType()) {
+ if (!getDerived().AlwaysRebuild() && T == E->getType() &&
+ !E->isCapturedByCopyInLambdaWithExplicitObjectParameter()) {
// Mark it referenced in the new context regardless.
// FIXME: this is a bit instantiation-specific.
getSema().MarkThisReferenced(E);
diff --git a/clang/test/CodeGenCXX/cxx2b-deducing-this.cpp
b/clang/test/CodeGenCXX/cxx2b-deducing-this.cpp
index 8a78463d3a495..7325121582324 100644
--- a/clang/test/CodeGenCXX/cxx2b-deducing-this.cpp
+++ b/clang/test/CodeGenCXX/cxx2b-deducing-this.cpp
@@ -264,3 +264,28 @@ void test() {
// CHECK: call void @_ZNH5P27971C1cERKS0_
// CHECK: call void @_ZN5P27971C1cEi
}
+
+// This used to crash because we weren’t instantiating a dependent 'this'.
+namespace GH154054 {
+struct S {
+ int x;
+ auto byval() {
+ return [*this](this auto) { return this->x; };
+ }
+};
+
+void main() {
+ S s{ 42 };
+
+ if ( s.byval()() != 42)
+ __builtin_abort();
+}
+
+struct s {
+ auto f() { return [*this](this auto) { return this; }; }
+};
+
+void f() {
+ s().f()();
+}
+}
>From 87d52bf09ac44f40ad635c6c448efe24185f3d8e Mon Sep 17 00:00:00 2001
From: Sirraide <aeternalm...@gmail.com>
Date: Tue, 19 Aug 2025 12:15:50 +0200
Subject: [PATCH 2/3] Add some check lines
---
clang/test/CodeGenCXX/cxx2b-deducing-this.cpp | 4 ++++
1 file changed, 4 insertions(+)
diff --git a/clang/test/CodeGenCXX/cxx2b-deducing-this.cpp
b/clang/test/CodeGenCXX/cxx2b-deducing-this.cpp
index 7325121582324..ba2f9c04e9a3d 100644
--- a/clang/test/CodeGenCXX/cxx2b-deducing-this.cpp
+++ b/clang/test/CodeGenCXX/cxx2b-deducing-this.cpp
@@ -274,9 +274,11 @@ struct S {
}
};
+// CHECK-LABEL: define {{.*}} void @_ZN8GH1540544mainEv
void main() {
S s{ 42 };
+ // CHECK: call {{.*}} i32 @_ZZN8GH1540541S5byvalEvENHUlT_E_clIS2_EEDaS1_
if ( s.byval()() != 42)
__builtin_abort();
}
@@ -285,7 +287,9 @@ struct s {
auto f() { return [*this](this auto) { return this; }; }
};
+// CHECK-LABEL: define {{.*}} void @_ZN8GH1540541fEv
void f() {
+ // CHECK: call {{.*}} ptr @_ZZN8GH1540541s1fEvENHUlT_E_clIS2_EEDaS1_
s().f()();
}
}
>From f1f4c938c21c017c1e821d07e79cb59c78072a88 Mon Sep 17 00:00:00 2001
From: Sirraide <aeternalm...@gmail.com>
Date: Tue, 19 Aug 2025 12:25:10 +0200
Subject: [PATCH 3/3] Add more check lines
---
clang/test/CodeGenCXX/cxx2b-deducing-this.cpp | 27 +++++++++++++++++--
1 file changed, 25 insertions(+), 2 deletions(-)
diff --git a/clang/test/CodeGenCXX/cxx2b-deducing-this.cpp
b/clang/test/CodeGenCXX/cxx2b-deducing-this.cpp
index ba2f9c04e9a3d..9664a866376ae 100644
--- a/clang/test/CodeGenCXX/cxx2b-deducing-this.cpp
+++ b/clang/test/CodeGenCXX/cxx2b-deducing-this.cpp
@@ -283,13 +283,36 @@ void main() {
__builtin_abort();
}
+// CHECK-LABEL: define {{.*}} i32
@_ZZN8GH1540541S5byvalEvENHUlT_E_clIS2_EEDaS1_(i32 %.coerce)
+// CHECK: entry:
+// CHECK: %0 = alloca %class.anon.11, align 4
+// CHECK: %coerce.dive = getelementptr inbounds nuw %class.anon.11, ptr %0,
i32 0, i32 0
+// CHECK: %coerce.dive1 = getelementptr inbounds nuw %"struct.GH154054::S",
ptr %coerce.dive, i32 0, i32 0
+// CHECK: store i32 %.coerce, ptr %coerce.dive1, align 4
+// CHECK: %1 = getelementptr inbounds nuw %class.anon.11, ptr %0, i32 0, i32 0
+// CHECK: %x = getelementptr inbounds nuw %"struct.GH154054::S", ptr %1, i32
0, i32 0
+// CHECK: %2 = load i32, ptr %x, align 4
+// CHECK: ret i32 %2
+
struct s {
- auto f() { return [*this](this auto) { return this; }; }
+ int q;
+ auto f() {
+ return [*this](this auto) { return this; };
+ }
};
// CHECK-LABEL: define {{.*}} void @_ZN8GH1540541fEv
void f() {
// CHECK: call {{.*}} ptr @_ZZN8GH1540541s1fEvENHUlT_E_clIS2_EEDaS1_
- s().f()();
+ s{}.f()();
}
+
+// CHECK-LABEL: define {{.*}} ptr
@_ZZN8GH1540541s1fEvENHUlT_E_clIS2_EEDaS1_(i32 %.coerce)
+// CHECK: entry:
+// CHECK: %0 = alloca %class.anon.12, align 4
+// CHECK: %coerce.dive = getelementptr inbounds nuw %class.anon.12, ptr %0,
i32 0, i32 0
+// CHECK: %coerce.dive1 = getelementptr inbounds nuw %"struct.GH154054::s",
ptr %coerce.dive, i32 0, i32 0
+// CHECK: store i32 %.coerce, ptr %coerce.dive1, align 4
+// CHECK: %1 = getelementptr inbounds nuw %class.anon.12, ptr %0, i32 0, i32 0
+// CHECK: ret ptr %1
}
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