cgo only supports integer-sized parameters

[Leopotam]

// native.h
typedef struct Vector2
{
    float x;
    float y;
} Vector2;

Vector2 Vector2Add(Vector2 v1, Vector2 v2)
{
    Vector2 result = {v1.x + v2.x, v1.y + v2.y};
    return result;
}

// main.go
package main

// #include "native.h"
import "C"
import "fmt"

func main() {
	a := C.Vector2{1, 2}
	b := C.Vector2{1, 2}
	c := C.Vector2Add(a, b)
	fmt.Println(c)
}

> go run main.go
{2 4}

> tinygo run main.go
{3 2}

> tinygo version
tinygo version 0.33.0 darwin/amd64 (using go version go1.23.2 and LLVM version 18.1.2)

[supremestranger]

Windows:

> tinygo.exe run main.go
{0 0}

> go run main.go
{2 4}

[dgryski]

Ugh, this has got to be calling convention differences for non-integer-sized objects.

[Leopotam]

Oh, cgo in tinygo supports only integer-sized objects - its not issue, nevermind then.

[dgryski]

Reopening because it's still a cgo bug/limitation.

[Leopotam]

@dgryski any workaround for this issue? Can I compile c-code as part of go-project to wasm-browser target with tinygo? Standard go-compiler doesnt support it.

[aykevl]

Matching the C ABI is a difficult problem, since this is basically an implementation detail between Clang and LLVM. There have been various proposals to expose this as a library, the most recent being https://discourse.llvm.org/t/rfc-an-abi-lowering-library-for-llvm/84495 (and https://github.com/llvm/llvm-project/pull/158329).

I hope one of these proposals will eventually be usable so we can finally fix this.