[clang] [C++20] Destroying delete and deleted destructors (PR #118800)
Aaron Ballman via cfe-commits
cfe-commits at lists.llvm.org
Fri Dec 6 05:10:40 PST 2024
https://github.com/AaronBallman updated https://github.com/llvm/llvm-project/pull/118800
>From 34d3d3000bc6096bbc9eb35ce85b6ceca50b91ca Mon Sep 17 00:00:00 2001
From: Aaron Ballman <aaron at aaronballman.com>
Date: Thu, 5 Dec 2024 08:31:24 -0500
Subject: [PATCH 1/4] [C++20] Destroying delete and deleted destructors
When a destroying delete overload is selected, the destructor is not
automatically called. Therefore, the destructor can be deleted without
causing the program to be ill-formed.
---
clang/docs/ReleaseNotes.rst | 2 ++
clang/lib/Sema/SemaExprCXX.cpp | 6 +++--
.../CXX/expr/expr.unary/expr.delete/p10.cpp | 22 +++++++++++++++++--
3 files changed, 26 insertions(+), 4 deletions(-)
diff --git a/clang/docs/ReleaseNotes.rst b/clang/docs/ReleaseNotes.rst
index e484eb7a76e63a..4a72e4046e2d03 100644
--- a/clang/docs/ReleaseNotes.rst
+++ b/clang/docs/ReleaseNotes.rst
@@ -663,6 +663,8 @@ Bug Fixes in This Version
- Fixed a crash when GNU statement expression contains invalid statement (#GH113468).
- Fixed a failed assertion when using ``__attribute__((noderef))`` on an
``_Atomic``-qualified type (#GH116124).
+- No longer incorrectly diagnosing use of a deleted destructor when the
+ selected overload of ``operator delete`` for that type is a destroying delete.
Bug Fixes to Compiler Builtins
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
diff --git a/clang/lib/Sema/SemaExprCXX.cpp b/clang/lib/Sema/SemaExprCXX.cpp
index db9ea7fb66e05a..45840dfa31ac92 100644
--- a/clang/lib/Sema/SemaExprCXX.cpp
+++ b/clang/lib/Sema/SemaExprCXX.cpp
@@ -3792,13 +3792,15 @@ Sema::ActOnCXXDelete(SourceLocation StartLoc, bool UseGlobal,
.HasSizeT;
}
- if (!PointeeRD->hasIrrelevantDestructor())
+ if (!PointeeRD->hasIrrelevantDestructor() &&
+ (!OperatorDelete || !OperatorDelete->isDestroyingOperatorDelete())) {
if (CXXDestructorDecl *Dtor = LookupDestructor(PointeeRD)) {
MarkFunctionReferenced(StartLoc,
- const_cast<CXXDestructorDecl*>(Dtor));
+ const_cast<CXXDestructorDecl *>(Dtor));
if (DiagnoseUseOfDecl(Dtor, StartLoc))
return ExprError();
}
+ }
CheckVirtualDtorCall(PointeeRD->getDestructor(), StartLoc,
/*IsDelete=*/true, /*CallCanBeVirtual=*/true,
diff --git a/clang/test/CXX/expr/expr.unary/expr.delete/p10.cpp b/clang/test/CXX/expr/expr.unary/expr.delete/p10.cpp
index aad2747dd32f24..b2c0a2c79695fc 100644
--- a/clang/test/CXX/expr/expr.unary/expr.delete/p10.cpp
+++ b/clang/test/CXX/expr/expr.unary/expr.delete/p10.cpp
@@ -1,7 +1,14 @@
-// RUN: %clang_cc1 -std=c++1z -verify %s
+// RUN: %clang_cc1 -std=c++20 -verify %s
using size_t = decltype(sizeof(0));
-namespace std { enum class align_val_t : size_t {}; }
+namespace std {
+ enum class align_val_t : size_t {};
+ struct destroying_delete_t {
+ explicit destroying_delete_t() = default;
+ };
+
+ inline constexpr destroying_delete_t destroying_delete{};
+}
// Aligned version is preferred over unaligned version,
// unsized version is preferred over sized version.
@@ -23,3 +30,14 @@ struct alignas(Align) B {
};
void f(B<__STDCPP_DEFAULT_NEW_ALIGNMENT__> *p) { delete p; }
void f(B<__STDCPP_DEFAULT_NEW_ALIGNMENT__ * 2> *p) { delete p; } // expected-error {{deleted}}
+
+// Ensure that a deleted destructor is acceptable when the selected overload
+// for operator delete is a destroying delete. See the comments in GH118660.
+struct S {
+ ~S() = delete;
+ void operator delete(S *, std::destroying_delete_t) noexcept {}
+};
+
+void foo(S *s) {
+ delete s; // Was rejected, is intended to be accepted.
+}
>From 133a8aa2934f9d6ed733e74af65180131d59cc91 Mon Sep 17 00:00:00 2001
From: Aaron Ballman <aaron at aaronballman.com>
Date: Thu, 5 Dec 2024 10:14:46 -0500
Subject: [PATCH 2/4] Update based on review feedback
* Added a standards reference
* Added a test case
* Fixed an issue the new test case identified
---
clang/lib/Sema/SemaExprCXX.cpp | 13 +++++++++++--
clang/test/CXX/expr/expr.unary/expr.delete/p10.cpp | 10 ++++++++++
2 files changed, 21 insertions(+), 2 deletions(-)
diff --git a/clang/lib/Sema/SemaExprCXX.cpp b/clang/lib/Sema/SemaExprCXX.cpp
index 45840dfa31ac92..6ac44ae7af28c3 100644
--- a/clang/lib/Sema/SemaExprCXX.cpp
+++ b/clang/lib/Sema/SemaExprCXX.cpp
@@ -3792,6 +3792,14 @@ Sema::ActOnCXXDelete(SourceLocation StartLoc, bool UseGlobal,
.HasSizeT;
}
+ // C++20 [expr.delete]p6: If the value of the operand of the delete-
+ // expression is not a null pointer value and the selected deallocation
+ // function (see below) is not a destroying operator delete, the delete-
+ // expression will invoke the destructor (if any) for the object or the
+ // elements of the array being deleted.
+ //
+ // This means we should not look at the destructor for a destroying
+ // delete operator, as that destructor is never called.
if (!PointeeRD->hasIrrelevantDestructor() &&
(!OperatorDelete || !OperatorDelete->isDestroyingOperatorDelete())) {
if (CXXDestructorDecl *Dtor = LookupDestructor(PointeeRD)) {
@@ -3831,9 +3839,10 @@ Sema::ActOnCXXDelete(SourceLocation StartLoc, bool UseGlobal,
MarkFunctionReferenced(StartLoc, OperatorDelete);
// Check access and ambiguity of destructor if we're going to call it.
- // Note that this is required even for a virtual delete.
+ // Note that this is required even for a virtual delete, but not for a
+ // destroying delete operator.
bool IsVirtualDelete = false;
- if (PointeeRD) {
+ if (PointeeRD && !OperatorDelete->isDestroyingOperatorDelete()) {
if (CXXDestructorDecl *Dtor = LookupDestructor(PointeeRD)) {
CheckDestructorAccess(Ex.get()->getExprLoc(), Dtor,
PDiag(diag::err_access_dtor) << PointeeElem);
diff --git a/clang/test/CXX/expr/expr.unary/expr.delete/p10.cpp b/clang/test/CXX/expr/expr.unary/expr.delete/p10.cpp
index b2c0a2c79695fc..aff3e2b449da37 100644
--- a/clang/test/CXX/expr/expr.unary/expr.delete/p10.cpp
+++ b/clang/test/CXX/expr/expr.unary/expr.delete/p10.cpp
@@ -38,6 +38,16 @@ struct S {
void operator delete(S *, std::destroying_delete_t) noexcept {}
};
+struct T {
+ void operator delete(T *, std::destroying_delete_t) noexcept {}
+private:
+ ~T();
+};
+
void foo(S *s) {
delete s; // Was rejected, is intended to be accepted.
}
+
+void bar(T *t) {
+ delete t; // Was rejected, is intended to be accepted.
+}
>From b42fb1350f95924fae0b5dd7a46d7bc4d46d3d29 Mon Sep 17 00:00:00 2001
From: Aaron Ballman <aaron at aaronballman.com>
Date: Thu, 5 Dec 2024 11:58:33 -0500
Subject: [PATCH 3/4] Fix one of the two failing tests, update release notes
It turns out someone filed an issue for this.
---
clang/docs/ReleaseNotes.rst | 3 ++-
clang/test/SemaCXX/cxx2a-destroying-delete.cpp | 12 ++++++------
2 files changed, 8 insertions(+), 7 deletions(-)
diff --git a/clang/docs/ReleaseNotes.rst b/clang/docs/ReleaseNotes.rst
index 4a72e4046e2d03..e6373b165b63df 100644
--- a/clang/docs/ReleaseNotes.rst
+++ b/clang/docs/ReleaseNotes.rst
@@ -664,7 +664,8 @@ Bug Fixes in This Version
- Fixed a failed assertion when using ``__attribute__((noderef))`` on an
``_Atomic``-qualified type (#GH116124).
- No longer incorrectly diagnosing use of a deleted destructor when the
- selected overload of ``operator delete`` for that type is a destroying delete.
+ selected overload of ``operator delete`` for that type is a destroying delete
+ (#GH46818).
Bug Fixes to Compiler Builtins
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
diff --git a/clang/test/SemaCXX/cxx2a-destroying-delete.cpp b/clang/test/SemaCXX/cxx2a-destroying-delete.cpp
index 25b985ef11d157..e986c6abfe8cec 100644
--- a/clang/test/SemaCXX/cxx2a-destroying-delete.cpp
+++ b/clang/test/SemaCXX/cxx2a-destroying-delete.cpp
@@ -146,17 +146,17 @@ namespace dtor_access {
struct S {
void operator delete(S *p, std::destroying_delete_t);
private:
- ~S(); // expected-note {{here}}
+ ~S();
};
- // FIXME: PR47474: GCC accepts this, and it seems somewhat reasonable to
- // allow, even though [expr.delete]p12 says this is ill-formed.
- void f() { delete new S; } // expected-error {{calling a private destructor}}
+ // C++20 [expr.delete]p12 says this is ill-formed, but GCC accepts and we
+ // filed CWG2889 to resolve in the same way.
+ void f() { delete new S; }
struct T {
void operator delete(T *, std::destroying_delete_t);
protected:
- virtual ~T(); // expected-note {{here}}
+ virtual ~T();
};
struct U : T {
@@ -165,7 +165,7 @@ namespace dtor_access {
~U() override;
};
- void g() { delete (T *)new U; } // expected-error {{calling a protected destructor}}
+ void g() { delete (T *)new U; }
}
namespace delete_from_new {
>From 7e690aed3104c3b60e2f9c006c892ef56bc2e8cc Mon Sep 17 00:00:00 2001
From: Aaron Ballman <aaron at aaronballman.com>
Date: Thu, 5 Dec 2024 13:11:11 -0500
Subject: [PATCH 4/4] Fix the other failing test case
A virtual destructor still needs to be accessible to a destroying
delete because the actual delete operator called depends on the dynamic
type of the pointer, not the static type.
---
clang/lib/Sema/SemaExprCXX.cpp | 53 ++++++++++++-------
.../CXX/expr/expr.unary/expr.delete/p10.cpp | 23 ++++++--
.../test/SemaCXX/cxx2a-destroying-delete.cpp | 4 +-
3 files changed, 56 insertions(+), 24 deletions(-)
diff --git a/clang/lib/Sema/SemaExprCXX.cpp b/clang/lib/Sema/SemaExprCXX.cpp
index 6ac44ae7af28c3..d1268acd0ec0ab 100644
--- a/clang/lib/Sema/SemaExprCXX.cpp
+++ b/clang/lib/Sema/SemaExprCXX.cpp
@@ -3768,6 +3768,28 @@ Sema::ActOnCXXDelete(SourceLocation StartLoc, bool UseGlobal,
DeclarationName DeleteName = Context.DeclarationNames.getCXXOperatorName(
ArrayForm ? OO_Array_Delete : OO_Delete);
+ // C++20 [expr.delete]p6: If the value of the operand of the delete-
+ // expression is not a null pointer value and the selected deallocation
+ // function (see below) is not a destroying operator delete, the delete-
+ // expression will invoke the destructor (if any) for the object or the
+ // elements of the array being deleted.
+ //
+ // This means we should not look at the destructor for a destroying
+ // delete operator, as that destructor is never called, unless the
+ // destructor is virtual (see [expr.delete]p8.1) because then the
+ // selected operator depends on the dynamic type of the pointer.
+ auto IsDtorCalled = [](const CXXMethodDecl *Dtor,
+ const FunctionDecl *OperatorDelete) {
+ if (!OperatorDelete)
+ return true;
+
+ if (!OperatorDelete->isDestroyingOperatorDelete())
+ return true;
+
+ // We have a destroying operator delete, so it depends on the dtor.
+ return Dtor->isVirtual();
+ };
+
if (PointeeRD) {
if (!UseGlobal &&
FindDeallocationFunction(StartLoc, PointeeRD, DeleteName,
@@ -3792,21 +3814,14 @@ Sema::ActOnCXXDelete(SourceLocation StartLoc, bool UseGlobal,
.HasSizeT;
}
- // C++20 [expr.delete]p6: If the value of the operand of the delete-
- // expression is not a null pointer value and the selected deallocation
- // function (see below) is not a destroying operator delete, the delete-
- // expression will invoke the destructor (if any) for the object or the
- // elements of the array being deleted.
- //
- // This means we should not look at the destructor for a destroying
- // delete operator, as that destructor is never called.
- if (!PointeeRD->hasIrrelevantDestructor() &&
- (!OperatorDelete || !OperatorDelete->isDestroyingOperatorDelete())) {
+ if (!PointeeRD->hasIrrelevantDestructor()) {
if (CXXDestructorDecl *Dtor = LookupDestructor(PointeeRD)) {
- MarkFunctionReferenced(StartLoc,
- const_cast<CXXDestructorDecl *>(Dtor));
- if (DiagnoseUseOfDecl(Dtor, StartLoc))
- return ExprError();
+ if (IsDtorCalled(Dtor, OperatorDelete)) {
+ MarkFunctionReferenced(StartLoc,
+ const_cast<CXXDestructorDecl *>(Dtor));
+ if (DiagnoseUseOfDecl(Dtor, StartLoc))
+ return ExprError();
+ }
}
}
@@ -3839,13 +3854,13 @@ Sema::ActOnCXXDelete(SourceLocation StartLoc, bool UseGlobal,
MarkFunctionReferenced(StartLoc, OperatorDelete);
// Check access and ambiguity of destructor if we're going to call it.
- // Note that this is required even for a virtual delete, but not for a
- // destroying delete operator.
+ // Note that this is required even for a virtual delete.
bool IsVirtualDelete = false;
- if (PointeeRD && !OperatorDelete->isDestroyingOperatorDelete()) {
+ if (PointeeRD) {
if (CXXDestructorDecl *Dtor = LookupDestructor(PointeeRD)) {
- CheckDestructorAccess(Ex.get()->getExprLoc(), Dtor,
- PDiag(diag::err_access_dtor) << PointeeElem);
+ if (IsDtorCalled(Dtor, OperatorDelete))
+ CheckDestructorAccess(Ex.get()->getExprLoc(), Dtor,
+ PDiag(diag::err_access_dtor) << PointeeElem);
IsVirtualDelete = Dtor->isVirtual();
}
}
diff --git a/clang/test/CXX/expr/expr.unary/expr.delete/p10.cpp b/clang/test/CXX/expr/expr.unary/expr.delete/p10.cpp
index aff3e2b449da37..b8d64fd7eeabb6 100644
--- a/clang/test/CXX/expr/expr.unary/expr.delete/p10.cpp
+++ b/clang/test/CXX/expr/expr.unary/expr.delete/p10.cpp
@@ -44,10 +44,27 @@ struct T {
~T();
};
-void foo(S *s) {
+void foo(S *s, T *t) {
delete s; // Was rejected, is intended to be accepted.
+ delete t; // Was rejected, is intended to be accepted.
}
-void bar(T *t) {
- delete t; // Was rejected, is intended to be accepted.
+// However, if the destructor is virtual, then it has to be accessible because
+// the behavior depends on which operator delete is selected and that is based
+// on the dynamic type of the pointer.
+struct U {
+ virtual ~U() = delete; // expected-note {{here}}
+ void operator delete(U *, std::destroying_delete_t) noexcept {}
+};
+
+struct V {
+ void operator delete(V *, std::destroying_delete_t) noexcept {}
+private:
+ virtual ~V(); // expected-note {{here}}
+};
+
+void bar(U *u, V *v) {
+ // Both should be rejected because they have virtual destructors.
+ delete u; // expected-error {{attempt to use a deleted function}}
+ delete v; // expected-error {{calling a private destructor of class 'V'}}
}
diff --git a/clang/test/SemaCXX/cxx2a-destroying-delete.cpp b/clang/test/SemaCXX/cxx2a-destroying-delete.cpp
index e986c6abfe8cec..bf0a64a77385c6 100644
--- a/clang/test/SemaCXX/cxx2a-destroying-delete.cpp
+++ b/clang/test/SemaCXX/cxx2a-destroying-delete.cpp
@@ -156,7 +156,7 @@ namespace dtor_access {
struct T {
void operator delete(T *, std::destroying_delete_t);
protected:
- virtual ~T();
+ virtual ~T(); // expected-note {{here}}
};
struct U : T {
@@ -165,7 +165,7 @@ namespace dtor_access {
~U() override;
};
- void g() { delete (T *)new U; }
+ void g() { delete (T *)new U; } // expected-error {{calling a protected destructor of class 'T'}}
}
namespace delete_from_new {
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