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Export abstract methods as pure virtual (#7578)

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`abstract fn` was exported to C++ as a plain virtual function rather
than a pure virtual one, so the class wasn't abstract and could be
instantiated from C++.

Abstract functions no longer get a thunk since there is no definition to
call. The tests are prefixed with `fail_` since an abstract class still
errors on `Core.Destroy` regardless.
This commit is contained in:
arhwx
2026-07-30 00:29:53 +00:00
committed by GitHub
parent 198e447e4a
commit 8f224222a1
3 changed files with 60 additions and 1 deletions
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toolchain/check/cpp/export.cpp
+4 -1
View File
@@ -825,7 +825,10 @@ static auto BuildCppToCarbonThunkDecl(Context& context, SemIR::LocId loc_id,
SemIR::Function::VirtualModifier::None &&
target.function.virtual_modifier !=
SemIR::Function::VirtualModifier::Override);
// TODO: Call setIsPureVirtual if VirtualModifier::Abstract is present.
if (target.function.virtual_modifier ==
SemIR::Function::VirtualModifier::Abstract) {
cast<clang::CXXMethodDecl>(thunk_function_decl)->setIsPureVirtual(true);
}
} else {
thunk_function_decl = clang::FunctionDecl::Create(
ast_context, target.decl_context, clang_loc, name_info, thunk_qual_type,
toolchain/check/cpp/generate_ast.cpp
+5
View File
@@ -544,6 +544,11 @@ auto CarbonExternalASTSource::CompleteType(clang::TagDecl* tag_decl) -> void {
method_decl,
MakeVirtualFunctionSignature(*context_, method_decl)),
.inst_id = function.first_decl_id()});
// An abstract function has no definition, so it doesn't need a thunk.
if (function.virtual_modifier ==
SemIR::Function::VirtualModifier::Abstract) {
continue;
}
pending_virtual_functions.push_back(
{.loc_id = SemIR::LocId(vtable_entry_id),
.function_id = callee_function.function_id,
toolchain/check/testdata/interop/cpp/class/export/base.carbon
Vendored
+51
View File
@@ -145,6 +145,57 @@ class Derived : public Carbon::Abstract {
};
''';
// --- fail_variable_with_abstract_method.carbon
library "[[@TEST_NAME]]";
import Cpp;
// TODO: We should support generating a base subobject destructor for an
// abstract class, even though we refuse to generate a complete object
// destructor.
// CHECK:STDERR: fail_variable_with_abstract_method.carbon:[[@LINE+4]]:1: error: cannot access member of interface `Core.Destroy` in type `Abstract` that does not implement that interface [MissingImplInMemberAccess]
// CHECK:STDERR: abstract class Abstract {
// CHECK:STDERR: ^~~~~~~~~~~~~~~~~~~~~~~~~
// CHECK:STDERR:
abstract class Abstract {
abstract fn F(self);
}
inline Cpp '''
// CHECK:STDERR: fail_variable_with_abstract_method.carbon:[[@LINE+7]]:18: error: variable type 'Carbon::Abstract' is an abstract class [CppInteropParseError]
// CHECK:STDERR: 24 | Carbon::Abstract x;
// CHECK:STDERR: | ^
// CHECK:STDERR: fail_variable_with_abstract_method.carbon:[[@LINE-7]]:22: note: unimplemented pure virtual method 'F' in 'Abstract' [CppInteropParseNote]
// CHECK:STDERR: 13 | abstract fn F(self);
// CHECK:STDERR: | ^
// CHECK:STDERR:
Carbon::Abstract x;
''';
// --- fail_todo_abstract_method_overridden_in_cpp.carbon
library "[[@TEST_NAME]]";
import Cpp;
// TODO: We should support generating a base subobject destructor for an
// abstract class, even though we refuse to generate a complete object
// destructor.
// CHECK:STDERR: fail_todo_abstract_method_overridden_in_cpp.carbon:[[@LINE+4]]:1: error: cannot access member of interface `Core.Destroy` in type `Abstract` that does not implement that interface [MissingImplInMemberAccess]
// CHECK:STDERR: abstract class Abstract {
// CHECK:STDERR: ^~~~~~~~~~~~~~~~~~~~~~~~~
// CHECK:STDERR:
abstract class Abstract {
abstract fn F(ref self);
}
// A C++ class that overrides the abstract method can be instantiated.
inline Cpp '''
struct Derived : Carbon::Abstract {
void F() & override {}
};
Derived d;
''';
// --- override_virtual_dtor.carbon
library "[[@TEST_NAME]]";