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C++ Interop: Support getting void* from C++ functions and passing void* it to C++ function #6279

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Merged
merged 12 commits into from
Oct 29, 2025
Merged

C++ Interop: Support getting void* from C++ functions and passing void* it to C++ function #6279

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9e73edf
C++ Interop: Support getting `void*` from C++ functions and passing `…
bricknerb Oct 27, 2025
f252405
Replace `<builtin Cpp.void>` with `Cpp.void` when stringifying `Cpp.v…
bricknerb Oct 28, 2025
6f40fed
Add tests for `void**` and `const void*`. Add support for `const void*`.
bricknerb Oct 28, 2025
6b7a510
Rename `CustomCppVoidType` to `CppVoidType`.
bricknerb Oct 28, 2025
3c45ed3
Move `StringifyInst()` for `CppVoidType` between `ConstType` and `Cus…
bricknerb Oct 28, 2025
68bbebd
Remove commented out code.
bricknerb Oct 28, 2025
2b17f69
In `TryMapVoidPointer()`, early return if there are no wrapper types.
bricknerb Oct 28, 2025
9b32c15
Merge branch 'main' into void2
bricknerb Oct 28, 2025
7a08553
Use `CppVoidType::TypeInstId` directly instead of indirectly.
bricknerb Oct 28, 2025
c942df1
Remove `pointer_iter` in `TryMapVoidPointer()` and erase the pointer …
bricknerb Oct 29, 2025
bce120f
Have a dedicate `BuildInfoForInst()` for `CppVoidType` and a TODO to …
bricknerb Oct 29, 2025
3b8ce38
Merge branch 'main' into void2
bricknerb Oct 29, 2025
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4 changes: 4 additions & 0 deletions toolchain/check/cpp/import.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -1137,6 +1137,9 @@ static auto MapBuiltinType(Context& context, SemIR::LocId loc_id,
context.ints().Add(ast_context.getTypeSize(qual_type))));
}
// TODO: Handle floating-point types that map to named aliases.
} else if (type.isVoidType()) {
return ExprAsType(context, Parse::NodeId::None,
SemIR::CppVoidType::TypeInstId);
}

return TypeExpr::None;
Expand Down Expand Up @@ -2116,6 +2119,7 @@ static auto LookupBuiltinTypes(Context& context, SemIR::LocId loc_id,
.Case("float", ast_context.FloatTy)
.Case("double", ast_context.DoubleTy)
.Case("long_double", ast_context.LongDoubleTy)
.Case("void", ast_context.VoidTy)
.Default(clang::QualType());
if (builtin_type.isNull()) {
return SemIR::InstId::None;
Expand Down
35 changes: 33 additions & 2 deletions toolchain/check/cpp/type_mapping.cpp
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Expand Up @@ -195,6 +195,33 @@ static auto MapNonWrapperType(Context& context, SemIR::InstId inst_id,
}
}

// Returns `void*` if the type is a wrapped `Cpp.void*`, consuming the pointer
// from `wrapper_types`. Otherwise returns no type.
static auto TryMapVoidPointer(Context& context, SemIR::TypeId type_id,
llvm::SmallVector<SemIR::TypeId>& wrapper_types)
-> clang::QualType {
if (type_id != SemIR::CppVoidType::TypeId || wrapper_types.empty()) {
return clang::QualType();
}

if (context.types().Is<SemIR::PointerType>(wrapper_types.back())) {
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@jonmeow jonmeow Oct 28, 2025

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There are probably other instructions that could be here which should be ignored, e.g. MaybeUnformedType. It might be worth thinking about whether a while loop here would be a good fit, but not asking for a change since wrapper_types doesn't support MaybeUnformedType right now either.

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@bricknerb bricknerb Oct 29, 2025

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Yes, this definitely makes sense to do when we can have a test that triggers this.

// `void*`.
wrapper_types.pop_back();
} else if (wrapper_types.size() >= 2 &&
context.types().Is<SemIR::ConstType>(wrapper_types.back()) &&
context.types().Is<SemIR::PointerType>(
wrapper_types[wrapper_types.size() - 2])) {
// `const void*`.
wrapper_types.erase(wrapper_types.end() - 2);
} else {
return clang::QualType();
}

return context.ast_context().getAttributedType(
clang::attr::TypeNonNull, context.ast_context().VoidPtrTy,
context.ast_context().VoidPtrTy);
}

// Maps a Carbon type to a C++ type. Accepts an InstId, representing a value
// whose type is mapped to a C++ type. Returns `clang::QualType` if the mapping
// succeeds, or `clang::QualType::isNull()` if the type is not supported.
Expand All @@ -219,9 +246,13 @@ static auto MapToCppType(Context& context, SemIR::InstId inst_id)
wrapper_types.push_back(orig_type_id);
}

clang::QualType mapped_type = MapNonWrapperType(context, inst_id, type_id);
clang::QualType mapped_type =
TryMapVoidPointer(context, type_id, wrapper_types);
if (mapped_type.isNull()) {
return mapped_type;
mapped_type = MapNonWrapperType(context, inst_id, type_id);
if (mapped_type.isNull()) {
return mapped_type;
}
}

for (auto wrapper_type_id : llvm::reverse(wrapper_types)) {
Expand Down
10 changes: 6 additions & 4 deletions toolchain/check/testdata/basics/raw_sem_ir/builtins.carbon
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Original file line number Diff line number Diff line change
Expand Up @@ -20,7 +20,7 @@
// CHECK:STDOUT: import_ir_insts: {}
// CHECK:STDOUT: clang_decls: {}
// CHECK:STDOUT: name_scopes:
// CHECK:STDOUT: name_scope00000000: {inst: inst0000000E, parent_scope: name_scope<none>, has_error: false, extended_scopes: [], names: {}}
// CHECK:STDOUT: name_scope00000000: {inst: inst0000000F, parent_scope: name_scope<none>, has_error: false, extended_scopes: [], names: {}}
// CHECK:STDOUT: entity_names: {}
// CHECK:STDOUT: cpp_global_vars: {}
// CHECK:STDOUT: functions: {}
Expand All @@ -42,6 +42,7 @@
// CHECK:STDOUT: 'inst(BoolType)': {kind: BoolType, type: type(TypeType)}
// CHECK:STDOUT: 'inst(BoundMethodType)': {kind: BoundMethodType, type: type(TypeType)}
// CHECK:STDOUT: 'inst(CharLiteralType)': {kind: CharLiteralType, type: type(TypeType)}
// CHECK:STDOUT: 'inst(CppVoidType)': {kind: CppVoidType, type: type(TypeType)}
// CHECK:STDOUT: 'inst(ErrorInst)': {kind: ErrorInst, type: type(Error)}
// CHECK:STDOUT: 'inst(FloatLiteralType)': {kind: FloatLiteralType, type: type(TypeType)}
// CHECK:STDOUT: 'inst(ImplWitnessTablePlaceholder)': {kind: ImplWitnessTablePlaceholder, type: type(TypeType)}
Expand All @@ -51,14 +52,15 @@
// CHECK:STDOUT: 'inst(SpecificFunctionType)': {kind: SpecificFunctionType, type: type(TypeType)}
// CHECK:STDOUT: 'inst(VtableType)': {kind: VtableType, type: type(TypeType)}
// CHECK:STDOUT: 'inst(WitnessType)': {kind: WitnessType, type: type(TypeType)}
// CHECK:STDOUT: inst0000000E: {kind: Namespace, arg0: name_scope00000000, arg1: inst<none>, type: type(inst(NamespaceType))}
// CHECK:STDOUT: inst0000000F: {kind: Namespace, arg0: name_scope00000000, arg1: inst<none>, type: type(inst(NamespaceType))}
// CHECK:STDOUT: constant_values:
// CHECK:STDOUT: values:
// CHECK:STDOUT: 'inst(TypeType)': concrete_constant(inst(TypeType))
// CHECK:STDOUT: 'inst(AutoType)': concrete_constant(inst(AutoType))
// CHECK:STDOUT: 'inst(BoolType)': concrete_constant(inst(BoolType))
// CHECK:STDOUT: 'inst(BoundMethodType)': concrete_constant(inst(BoundMethodType))
// CHECK:STDOUT: 'inst(CharLiteralType)': concrete_constant(inst(CharLiteralType))
// CHECK:STDOUT: 'inst(CppVoidType)': concrete_constant(inst(CppVoidType))
// CHECK:STDOUT: 'inst(ErrorInst)': concrete_constant(inst(ErrorInst))
// CHECK:STDOUT: 'inst(FloatLiteralType)': concrete_constant(inst(FloatLiteralType))
// CHECK:STDOUT: 'inst(ImplWitnessTablePlaceholder)': concrete_constant(inst(ImplWitnessTablePlaceholder))
Expand All @@ -68,13 +70,13 @@
// CHECK:STDOUT: 'inst(SpecificFunctionType)': concrete_constant(inst(SpecificFunctionType))
// CHECK:STDOUT: 'inst(VtableType)': concrete_constant(inst(VtableType))
// CHECK:STDOUT: 'inst(WitnessType)': concrete_constant(inst(WitnessType))
// CHECK:STDOUT: inst0000000E: concrete_constant(inst0000000E)
// CHECK:STDOUT: inst0000000F: concrete_constant(inst0000000F)
// CHECK:STDOUT: symbolic_constants: {}
// CHECK:STDOUT: inst_blocks:
// CHECK:STDOUT: inst_block_empty: {}
// CHECK:STDOUT: exports: {}
// CHECK:STDOUT: imports: {}
// CHECK:STDOUT: global_init: {}
// CHECK:STDOUT: inst_block60000004:
// CHECK:STDOUT: 0: inst0000000E
// CHECK:STDOUT: 0: inst0000000F
// CHECK:STDOUT: ...
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