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[Carbon/C++ interop] Add support for C++ overloaded functions (#5891)

Browse Source 
As proposed in [Carbon: C++ interop for overloaded functions and
function
templates](https://docs.google.com/document/d/1KUxumZtNe3mY3TsjW2s_ZADOlAaFlrtsLKHVILtqIaM/edit?tab=t.0),
Clang is used to perform the overload resolution using C++ rules, when
an overloaded C++ set is called from Carbon. Once a function is
selected, it's converted into a Carbon function and called using the
Carbon rules including argument conversions.

A single non-templated function is treated the same way as an overload
set and the same rules apply for its call.
Template functions are not supported yet.

Demo:

a) Non-templated function calls:

```c++
// --- overloads.h

auto foo(int a, short b) -> void;
auto foo(double a) -> void;
auto foo(int a) -> void;
```

```c++
// overloads.cpp

#include "overloads.h"
#include <cstdio>

auto foo(int a, short b) -> void {
  printf("hello from foo_int_short(%d, %d) \n", a, b);
}
auto foo(double a) -> void { printf("hello from foo_double(%f) \n", a); }
auto foo(int a) -> void { printf("hello from foo_int(%d) \n", a); }
```
```c++
library "Main";

import Cpp library "overloads.h";

fn Run() -> i32 {
  Cpp.foo(1.1 as f64);
  return 0;
}
```
```
$ clang -c overloads.cpp 
$ bazel-bin/toolchain/carbon compile main.carbon
$ bazel-bin/toolchain/carbon link overloads.o main.o --output=demo
$ ./demo
hello from foo_double(1.100000) 
```

b) Constructors:
```c++
// --- constructor_overloads.h
class C {
 public:
  C();
  C(int a, int b);
};
```

```c++
// constructor_overloads.cpp
#include "constructor_overloads.h"
#include <cstdio>

C::C() { printf("hello from C() \n"); }
C::C(int a, int b) { printf("hello from C(%d, %d) \n", a, b); }
```
```c++
library "Main";

import Cpp library "constructor_overloads.h";

fn Run() -> i32 {
  let c1: Cpp.C = Cpp.C.C();
  let c2: Cpp.C = Cpp.C.C(1, 2);
  return 0;
}
```

```
$ clang -c constructor_overloads.cpp 
$ bazel-bin/toolchain/carbon compile main.carbon
$ bazel-bin/toolchain/carbon link constructor_overloads.o main.o \--output=demo
$ ./demo
hello from C() 
hello from C(1, 2) 
```


Follow-ups:

- `Cpp.foo({})` - proper handling of struct literals as call args.
- Fix access for overloaded sets.
- Fix tests:
- Method calls: `error: missing object argument in method call
[MissingObjectInMethodCall]` in tests.
    - Fix `toolchain/check/testdata/interop/cpp/import.carbon` test.
    - Fix `enums` support.
    - Fix `str` -> `std::string_view` mapping.


Part of #5915
This commit is contained in:
Ivana Ivanovska
2025-09-15 12:29:49 +00:00
committed by GitHub
parent 20ac6b9270
commit 12ddfb9c7c
61 changed files with 4633 additions and 2252 deletions
Download Patch File Download Diff File Expand all files Collapse all files
toolchain/check/testdata/interop/cpp/stdlib/string_view.carbon
Vendored
+27 -36
View File
@@ -10,6 +10,8 @@
// TIP: To dump output, run:
// TIP: bazel run //toolchain/testing:file_test -- --dump_output --file_tests=toolchain/check/testdata/interop/cpp/stdlib/string_view.carbon
// TODO: Tests marked as `fail_todo_5891_` to fixed as a follow-up of https://github.com/carbon-language/carbon-lang/pull/5891.
// --- string_view.h
namespace std {
@@ -36,7 +38,7 @@ namespace std {
auto Consume(std::string_view sv) -> void;
auto Produce() -> std::string_view;
// --- import_multiple.carbon
// --- fail_todo_5891_import_multiple.carbon
library "[[@TEST_NAME]]";
@@ -44,6 +46,13 @@ import Cpp library "string_view.h";
//@dump-sem-ir-begin
fn F() {
// CHECK:STDERR: fail_todo_5891_import_multiple.carbon:[[@LINE+7]]:3: error: call argument of type `Core.String` is not supported [CppCallArgTypeNotSupported]
// CHECK:STDERR: Cpp.Consume("hello");
// CHECK:STDERR: ^~~~~~~~~~~~~~~~~~~~
// CHECK:STDERR: fail_todo_5891_import_multiple.carbon:[[@LINE+4]]:3: note: in call to Cpp function here [InCallToCppFunction]
// CHECK:STDERR: Cpp.Consume("hello");
// CHECK:STDERR: ^~~~~~~~~~~~~~~~~~~~
// CHECK:STDERR:
Cpp.Consume("hello");
}
//@dump-sem-ir-end
@@ -54,7 +63,7 @@ fn G() -> str {
}
//@dump-sem-ir-end
// CHECK:STDOUT: --- import_multiple.carbon
// CHECK:STDOUT: --- fail_todo_5891_import_multiple.carbon
// CHECK:STDOUT:
// CHECK:STDOUT: constants {
// CHECK:STDOUT: %F.type: type = fn_type @F [concrete]
@@ -66,44 +75,29 @@ fn G() -> str {
// CHECK:STDOUT: %int_8: Core.IntLiteral = int_value 8 [concrete]
// CHECK:STDOUT: %u8: type = class_type @UInt, @UInt(%int_8) [concrete]
// CHECK:STDOUT: %ptr.3e8: type = ptr_type %u8 [concrete]
// CHECK:STDOUT: %pattern_type.461: type = pattern_type %String [concrete]
// CHECK:STDOUT: %Consume.type: type = fn_type @Consume [concrete]
// CHECK:STDOUT: %Consume: %Consume.type = struct_value () [concrete]
// CHECK:STDOUT: %ptr.85f: type = ptr_type %String [concrete]
// CHECK:STDOUT: %Consume__carbon_thunk.type: type = fn_type @Consume__carbon_thunk [concrete]
// CHECK:STDOUT: %Consume__carbon_thunk: %Consume__carbon_thunk.type = struct_value () [concrete]
// CHECK:STDOUT: %.fd2: type = cpp_overload_set_type @Produce [concrete]
// CHECK:STDOUT: %empty_struct.c28: %.fd2 = struct_value () [concrete]
// CHECK:STDOUT: %str: %ptr.3e8 = string_literal "hello" [concrete]
// CHECK:STDOUT: %int_5: %u64 = int_value 5 [concrete]
// CHECK:STDOUT: %String.val: %String = struct_value (%str, %int_5) [concrete]
// CHECK:STDOUT: %pattern_type.461: type = pattern_type %String [concrete]
// CHECK:STDOUT: %G.type: type = fn_type @G [concrete]
// CHECK:STDOUT: %G: %G.type = struct_value () [concrete]
// CHECK:STDOUT: %Produce.type: type = fn_type @Produce [concrete]
// CHECK:STDOUT: %Produce: %Produce.type = struct_value () [concrete]
// CHECK:STDOUT: %.a47: type = cpp_overload_set_type @Produce__carbon_thunk [concrete]
// CHECK:STDOUT: %empty_struct.ab9: %.a47 = struct_value () [concrete]
// CHECK:STDOUT: %ptr.85f: type = ptr_type %String [concrete]
// CHECK:STDOUT: %Produce__carbon_thunk.type: type = fn_type @Produce__carbon_thunk [concrete]
// CHECK:STDOUT: %Produce__carbon_thunk: %Produce__carbon_thunk.type = struct_value () [concrete]
// CHECK:STDOUT: }
// CHECK:STDOUT:
// CHECK:STDOUT: imports {
// CHECK:STDOUT: %Cpp: <namespace> = namespace file.%Cpp.import_cpp, [concrete] {
// CHECK:STDOUT: .Consume = %Consume.decl
// CHECK:STDOUT: .Produce = %Produce.decl
// CHECK:STDOUT: .Consume = %.f17
// CHECK:STDOUT: .Produce = %.5d1
// CHECK:STDOUT: import Cpp//...
// CHECK:STDOUT: }
// CHECK:STDOUT: %Consume.decl: %Consume.type = fn_decl @Consume [concrete = constants.%Consume] {
// CHECK:STDOUT: <elided>
// CHECK:STDOUT: } {
// CHECK:STDOUT: <elided>
// CHECK:STDOUT: }
// CHECK:STDOUT: %Consume__carbon_thunk.decl: %Consume__carbon_thunk.type = fn_decl @Consume__carbon_thunk [concrete = constants.%Consume__carbon_thunk] {
// CHECK:STDOUT: <elided>
// CHECK:STDOUT: } {
// CHECK:STDOUT: <elided>
// CHECK:STDOUT: }
// CHECK:STDOUT: %Produce.decl: %Produce.type = fn_decl @Produce [concrete = constants.%Produce] {
// CHECK:STDOUT: <elided>
// CHECK:STDOUT: } {
// CHECK:STDOUT: <elided>
// CHECK:STDOUT: }
// CHECK:STDOUT: %.f17: %.fd2 = cpp_overload_set_value @Produce [concrete = constants.%empty_struct.c28]
// CHECK:STDOUT: %.5d1: %.a47 = cpp_overload_set_value @Produce__carbon_thunk [concrete = constants.%empty_struct.ab9]
// CHECK:STDOUT: %Produce__carbon_thunk.decl: %Produce__carbon_thunk.type = fn_decl @Produce__carbon_thunk [concrete = constants.%Produce__carbon_thunk] {
// CHECK:STDOUT: <elided>
// CHECK:STDOUT: } {
@@ -125,24 +119,21 @@ fn G() -> str {
// CHECK:STDOUT: fn @F() {
// CHECK:STDOUT: !entry:
// CHECK:STDOUT: %Cpp.ref: <namespace> = name_ref Cpp, imports.%Cpp [concrete = imports.%Cpp]
// CHECK:STDOUT: %Consume.ref: %Consume.type = name_ref Consume, imports.%Consume.decl [concrete = constants.%Consume]
// CHECK:STDOUT: %Consume.ref: %.fd2 = name_ref Consume, imports.%.f17 [concrete = constants.%empty_struct.c28]
// CHECK:STDOUT: %str: %ptr.3e8 = string_literal "hello" [concrete = constants.%str]
// CHECK:STDOUT: %int_5: %u64 = int_value 5 [concrete = constants.%int_5]
// CHECK:STDOUT: %String.val: %String = struct_value (%str, %int_5) [concrete = constants.%String.val]
// CHECK:STDOUT: %.loc8: ref %String = value_as_ref %String.val
// CHECK:STDOUT: %addr: %ptr.85f = addr_of %.loc8
// CHECK:STDOUT: %Consume__carbon_thunk.call: init %empty_tuple.type = call imports.%Consume__carbon_thunk.decl(%addr)
// CHECK:STDOUT: return
// CHECK:STDOUT: }
// CHECK:STDOUT:
// CHECK:STDOUT: fn @G() -> %return.param: %String {
// CHECK:STDOUT: !entry:
// CHECK:STDOUT: %Cpp.ref: <namespace> = name_ref Cpp, imports.%Cpp [concrete = imports.%Cpp]
// CHECK:STDOUT: %Produce.ref: %Produce.type = name_ref Produce, imports.%Produce.decl [concrete = constants.%Produce]
// CHECK:STDOUT: %.loc13: ref %String = splice_block %return {}
// CHECK:STDOUT: %addr: %ptr.85f = addr_of %.loc13
// CHECK:STDOUT: %Produce.ref: %.a47 = name_ref Produce, imports.%.5d1 [concrete = constants.%empty_struct.ab9]
// CHECK:STDOUT: %.loc20: ref %String = splice_block %return {}
// CHECK:STDOUT: %addr: %ptr.85f = addr_of %.loc20
// CHECK:STDOUT: %Produce__carbon_thunk.call: init %empty_tuple.type = call imports.%Produce__carbon_thunk.decl(%addr)
// CHECK:STDOUT: %.loc14: init %String = in_place_init %Produce__carbon_thunk.call, %.loc13
// CHECK:STDOUT: return %.loc14 to %return
// CHECK:STDOUT: %.loc21: init %String = in_place_init %Produce__carbon_thunk.call, %.loc20
// CHECK:STDOUT: return %.loc21 to %return
// CHECK:STDOUT: }
// CHECK:STDOUT: