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Superficial support for exporting complete class types to C++. (#7029)

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We don't yet populate the bases or fields, so the class types show up as
empty classes in C++ for now. But we do allow calls to static member
functions.
This commit is contained in:
Richard Smith
2026-04-08 19:29:25 +00:00
committed by GitHub
parent 9f1a0c816c
commit b74e0d1260
7 changed files with 417 additions and 37 deletions
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toolchain/check/cpp/export.cpp
+37 -18
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@@ -21,7 +21,6 @@ namespace Carbon::Check {
// The resulting decl is used to allow a generated C++ function to call
// a generated Carbon function.
static auto BuildCppFunctionDeclForCarbonFn(Context& context,
clang::DeclContext& decl_context,
SemIR::LocId loc_id,
SemIR::FunctionId function_id)
-> clang::FunctionDecl* {
@@ -57,11 +56,9 @@ static auto BuildCppFunctionDeclForCarbonFn(Context& context,
function.name_id);
auto* function_decl = clang::FunctionDecl::Create(
context.ast_context(), &decl_context,
/*StartLoc=*/clang_loc,
/*NLoc=*/clang_loc, clang::DeclarationName(identifier_info),
cpp_function_type,
/*TInfo=*/nullptr, clang::SC_Extern);
context.ast_context(), context.ast_context().getTranslationUnitDecl(),
/*StartLoc=*/clang_loc, /*NLoc=*/clang_loc, identifier_info,
cpp_function_type, /*TInfo=*/nullptr, clang::SC_Extern);
// Build parameter decls.
llvm::SmallVector<clang::ParmVarDecl*> param_var_decls;
@@ -85,22 +82,42 @@ static auto BuildCppFunctionDeclForCarbonFn(Context& context,
// Create the declaration of the C++ thunk.
static auto BuildCppToCarbonThunkDecl(
Context& context, SemIR::LocId loc_id, clang::DeclarationName thunk_name,
Context& context, SemIR::LocId loc_id, clang::DeclContext* decl_context,
clang::DeclarationName thunk_name,
llvm::ArrayRef<clang::QualType> thunk_param_types) -> clang::FunctionDecl* {
clang::ASTContext& ast_context = context.ast_context();
auto clang_loc = GetCppLocation(context, loc_id);
clang::DeclarationNameInfo name_info(thunk_name, clang_loc);
auto ext_proto_info = clang::FunctionProtoType::ExtProtoInfo();
clang::QualType thunk_function_type = ast_context.getFunctionType(
ast_context.VoidTy, thunk_param_types, ext_proto_info);
clang::DeclContext* decl_context = ast_context.getTranslationUnitDecl();
auto* tinfo =
ast_context.getTrivialTypeSourceInfo(thunk_function_type, clang_loc);
clang::FunctionDecl* thunk_function_decl = clang::FunctionDecl::Create(
ast_context, decl_context, clang_loc, clang_loc, thunk_name,
thunk_function_type, tinfo, clang::SC_Static);
const bool uses_fp_intrin = false;
const bool inline_specified = true;
const auto constexpr_kind = clang::ConstexprSpecKind::Unspecified;
const auto trailing_requires_clause = clang::AssociatedConstraint();
clang::FunctionDecl* thunk_function_decl = nullptr;
if (auto* parent_class = dyn_cast<clang::CXXRecordDecl>(decl_context)) {
// TODO: Support non-static methods.
thunk_function_decl = clang::CXXMethodDecl::Create(
ast_context, parent_class, clang_loc, name_info, thunk_function_type,
tinfo, clang::SC_Static, uses_fp_intrin, inline_specified,
constexpr_kind, clang_loc, trailing_requires_clause);
// TODO: Map Carbon access to C++ access.
thunk_function_decl->setAccess(clang::AS_public);
} else {
thunk_function_decl = clang::FunctionDecl::Create(
ast_context, decl_context, clang_loc, name_info, thunk_function_type,
tinfo, clang::SC_None, uses_fp_intrin, inline_specified,
/*hasWrittenPrototype=*/true, constexpr_kind, trailing_requires_clause);
}
decl_context->addDecl(thunk_function_decl);
llvm::SmallVector<clang::ParmVarDecl*> param_var_decls;
@@ -113,9 +130,11 @@ static auto BuildCppToCarbonThunkDecl(
}
thunk_function_decl->setParams(param_var_decls);
// Set always_inline.
// Force the thunk to be inlined and discarded.
thunk_function_decl->addAttr(
clang::AlwaysInlineAttr::CreateImplicit(ast_context));
thunk_function_decl->addAttr(
clang::InternalLinkageAttr::CreateImplicit(ast_context));
return thunk_function_decl;
}
@@ -151,8 +170,8 @@ static auto BuildCppToCarbonThunkBody(clang::Sema& sema,
// with `MapToCppType`. (Note that the target function here is the
// callee of the Carbon thunk.)
static auto BuildCppToCarbonThunk(
Context& context, SemIR::LocId loc_id, llvm::StringRef base_name,
clang::FunctionDecl* carbon_function_decl,
Context& context, SemIR::LocId loc_id, clang::DeclContext* decl_context,
llvm::StringRef base_name, clang::FunctionDecl* carbon_function_decl,
llvm::ArrayRef<SemIR::TypeId> callee_param_type_ids)
-> clang::FunctionDecl* {
// Create the thunk's name.
@@ -170,8 +189,8 @@ static auto BuildCppToCarbonThunk(
param_types.push_back(cpp_type);
}
auto* thunk_function_decl =
BuildCppToCarbonThunkDecl(context, loc_id, &thunk_ident, param_types);
auto* thunk_function_decl = BuildCppToCarbonThunkDecl(
context, loc_id, decl_context, &thunk_ident, param_types);
// Build the thunk function body.
clang::Sema& sema = context.clang_sema();
@@ -258,13 +277,13 @@ auto GetReverseInteropFunctionDecl(Context& context, SemIR::LocId loc_id,
// Create a `clang::FunctionDecl` that can be used to call the Carbon thunk.
auto* carbon_function_decl = BuildCppFunctionDeclForCarbonFn(
context, decl_context, loc_id, carbon_thunk_function_id);
context, loc_id, carbon_thunk_function_id);
if (!carbon_function_decl) {
return nullptr;
}
// Create a C++ thunk that calls the Carbon thunk.
return BuildCppToCarbonThunk(context, loc_id,
return BuildCppToCarbonThunk(context, loc_id, &decl_context,
context.names().GetFormatted(callee.name_id),
carbon_function_decl, callee_param_type_ids);
}