logan-5 created this revision.
logan-5 added reviewers: rsmith, yamauchi.
logan-5 added a project: clang.
Herald added a subscriber: cfe-commits.
Marking a class' destructor `final` prevents the class from being inherited
from. However, it is a subtle and awkward way to express that at best, and
unintended at worst. It may also generate worse code (in other compilers) than
marking the class itself `final`. For these reasons, this revision adds a
warning for nonfinal classes with final destructors, with a note to suggest
marking the class final to silence the warning.
See https://reviews.llvm.org/D66621 for more background.
Repository:
rC Clang
https://reviews.llvm.org/D66711
Files:
clang/include/clang/Basic/DiagnosticGroups.td
clang/include/clang/Basic/DiagnosticSemaKinds.td
clang/lib/Sema/SemaDeclCXX.cpp
clang/test/SemaCXX/warn-final-dtor-nonfinal-class.cpp
Index: clang/test/SemaCXX/warn-final-dtor-nonfinal-class.cpp
===================================================================
--- /dev/null
+++ clang/test/SemaCXX/warn-final-dtor-nonfinal-class.cpp
@@ -0,0 +1,13 @@
+// RUN: %clang_cc1 -fsyntax-only -std=c++11 -verify %s
-Wfinal-dtor-non-final-class
+
+class A {
+ ~A();
+};
+
+class B { // expected-note {{mark 'B' as 'final' to silence this warning}}
+ virtual ~B() final; // expected-warning {{class with destructor marked
'final' cannot be inherited from}}
+};
+
+class C final {
+ virtual ~C() final;
+};
Index: clang/lib/Sema/SemaDeclCXX.cpp
===================================================================
--- clang/lib/Sema/SemaDeclCXX.cpp
+++ clang/lib/Sema/SemaDeclCXX.cpp
@@ -6235,6 +6235,19 @@
}
}
+ // Warn if the class has a final destructor but is not itself marked final.
+ if (!Record->hasAttr<FinalAttr>()) {
+ if (CXXDestructorDecl *dtor = Record->getDestructor()) {
+ if (FinalAttr *FA = dtor->getAttr<FinalAttr>()) {
+ Diag(FA->getLocation(), diag::warn_final_destructor_nonfinal_class)
+ << FA->isSpelledAsSealed();
+ Diag(Record->getLocation(),
diag::note_final_destructor_nonfinal_class_silence)
+ << Context.getRecordType(Record)
+ << FA->isSpelledAsSealed();
+ }
+ }
+ }
+
// See if trivial_abi has to be dropped.
if (Record->hasAttr<TrivialABIAttr>())
checkIllFormedTrivialABIStruct(*Record);
Index: clang/include/clang/Basic/DiagnosticSemaKinds.td
===================================================================
--- clang/include/clang/Basic/DiagnosticSemaKinds.td
+++ clang/include/clang/Basic/DiagnosticSemaKinds.td
@@ -2201,6 +2201,11 @@
"base %0 is marked '%select{final|sealed}1'">;
def warn_abstract_final_class : Warning<
"abstract class is marked '%select{final|sealed}0'">,
InGroup<AbstractFinalClass>;
+def warn_final_destructor_nonfinal_class : Warning<
+ "class with destructor marked '%select{final|sealed}0' cannot be inherited
from">,
+ InGroup<FinalDtorNonFinalClass>;
+def note_final_destructor_nonfinal_class_silence : Note<
+ "mark %0 as '%select{final|sealed}1' to silence this warning">;
// C++11 attributes
def err_repeat_attribute : Error<"%0 attribute cannot be repeated">;
Index: clang/include/clang/Basic/DiagnosticGroups.td
===================================================================
--- clang/include/clang/Basic/DiagnosticGroups.td
+++ clang/include/clang/Basic/DiagnosticGroups.td
@@ -114,6 +114,7 @@
[DeleteNonAbstractNonVirtualDtor,
DeleteAbstractNonVirtualDtor]>;
def AbstractFinalClass : DiagGroup<"abstract-final-class">;
+def FinalDtorNonFinalClass : DiagGroup<"final-dtor-non-final-class">;
def CXX11CompatDeprecatedWritableStr :
DiagGroup<"c++11-compat-deprecated-writable-strings">;
Index: clang/test/SemaCXX/warn-final-dtor-nonfinal-class.cpp
===================================================================
--- /dev/null
+++ clang/test/SemaCXX/warn-final-dtor-nonfinal-class.cpp
@@ -0,0 +1,13 @@
+// RUN: %clang_cc1 -fsyntax-only -std=c++11 -verify %s -Wfinal-dtor-non-final-class
+
+class A {
+ ~A();
+};
+
+class B { // expected-note {{mark 'B' as 'final' to silence this warning}}
+ virtual ~B() final; // expected-warning {{class with destructor marked 'final' cannot be inherited from}}
+};
+
+class C final {
+ virtual ~C() final;
+};
Index: clang/lib/Sema/SemaDeclCXX.cpp
===================================================================
--- clang/lib/Sema/SemaDeclCXX.cpp
+++ clang/lib/Sema/SemaDeclCXX.cpp
@@ -6235,6 +6235,19 @@
}
}
+ // Warn if the class has a final destructor but is not itself marked final.
+ if (!Record->hasAttr<FinalAttr>()) {
+ if (CXXDestructorDecl *dtor = Record->getDestructor()) {
+ if (FinalAttr *FA = dtor->getAttr<FinalAttr>()) {
+ Diag(FA->getLocation(), diag::warn_final_destructor_nonfinal_class)
+ << FA->isSpelledAsSealed();
+ Diag(Record->getLocation(), diag::note_final_destructor_nonfinal_class_silence)
+ << Context.getRecordType(Record)
+ << FA->isSpelledAsSealed();
+ }
+ }
+ }
+
// See if trivial_abi has to be dropped.
if (Record->hasAttr<TrivialABIAttr>())
checkIllFormedTrivialABIStruct(*Record);
Index: clang/include/clang/Basic/DiagnosticSemaKinds.td
===================================================================
--- clang/include/clang/Basic/DiagnosticSemaKinds.td
+++ clang/include/clang/Basic/DiagnosticSemaKinds.td
@@ -2201,6 +2201,11 @@
"base %0 is marked '%select{final|sealed}1'">;
def warn_abstract_final_class : Warning<
"abstract class is marked '%select{final|sealed}0'">, InGroup<AbstractFinalClass>;
+def warn_final_destructor_nonfinal_class : Warning<
+ "class with destructor marked '%select{final|sealed}0' cannot be inherited from">,
+ InGroup<FinalDtorNonFinalClass>;
+def note_final_destructor_nonfinal_class_silence : Note<
+ "mark %0 as '%select{final|sealed}1' to silence this warning">;
// C++11 attributes
def err_repeat_attribute : Error<"%0 attribute cannot be repeated">;
Index: clang/include/clang/Basic/DiagnosticGroups.td
===================================================================
--- clang/include/clang/Basic/DiagnosticGroups.td
+++ clang/include/clang/Basic/DiagnosticGroups.td
@@ -114,6 +114,7 @@
[DeleteNonAbstractNonVirtualDtor,
DeleteAbstractNonVirtualDtor]>;
def AbstractFinalClass : DiagGroup<"abstract-final-class">;
+def FinalDtorNonFinalClass : DiagGroup<"final-dtor-non-final-class">;
def CXX11CompatDeprecatedWritableStr :
DiagGroup<"c++11-compat-deprecated-writable-strings">;
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