On Thu, Feb 16, 2023 at 2:38 AM Jan <pfei...@gmail.com> wrote:
>
> Apologies, actually it was trickier than I thought, the issue happens in not
> fully defined C types only. So here is an example that runs in go 1.19.5, but
> fails in go 1.20
>
> ```
> package main
>
> /*
> // Forward reference of C++ types.
> struct SomeType;
> typedef struct SomeType SomeType;
>
> // Fully defined type.
> typedef struct {
> char C;
> } FullyDefinedType;
> */
> import "C"
> import (
> "fmt"
> )
>
> type Wrapper[T any] struct {
> P *T
> }
>
> type SomeTypeHolder struct {
> *Wrapper[C.SomeType]
> }
>
> type FullyDefinedTypeHolder struct {
> *Wrapper[C.FullyDefinedType]
> }
>
> func main() {
> //var p *C.SomeType
> var x SomeTypeHolder
> var y FullyDefinedTypeHolder
> fmt.Printf("x.Wrapper=%x\n", x.Wrapper)
> fmt.Printf("y.Wrapper=%x\n", y.Wrapper)
> }
> ```
>
> In go 1.19.5 it prints:
>
> $ go run .
> x.Wrapper=0
> y.Wrapper=0
>
> In go 1.20 it prints:
>
> $ go run .
> # ...
> ./main.go:22:3: cannot use incomplete (or unallocatable) type as a type
> argument: main._Ctype_struct_SomeType
Giving an error here is https://go.dev/issue/54765. That is, fixing
that issue in 1.20 is what causes this program to not compile.
Ian
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