Cannot use len(s) (value of type int) as uintptr value in assignment

[StarpTech]

Hi, I see the following error when compiling a program with tinygo. Is it unsupported by design?

❯ tinygo build -o hello ./main.go
# github.com/cespare/xxhash
../../../go/pkg/mod/github.com/cespare/[email protected]/xxhash_unsafe.go:27:11: cannot use len(s) (value of type int) as uintptr value in assignment
../../../go/pkg/mod/github.com/cespare/[email protected]/xxhash_unsafe.go:28:11: cannot use len(s) (value of type int) as uintptr value in assignment

Source: https://github.com/cespare/xxhash/blob/569f7c8abf1f58d9043ab804d364483cb1c853b6/xxhash_unsafe.go#L27

I also saw similar issues in https://github.com/tidwall/gjson/blob/5c2e4b382486589dad7478130a364ee2fa6a068b/gjson_ngae.go#L74

[aykevl]

This is a duplicate of #1284.

In short, the code is not portable. However, in this case it's easy to work around it. This slightly changed version also compiles under TinyGo, by using the fact that StringHeader and SliceHeader all use the same type for the Len and Cap fields:

func Sum64String(s string) uint64 {
	// See https://groups.google.com/d/msg/golang-nuts/dcjzJy-bSpw/tcZYBzQqAQAJ
	// for some discussion about this unsafe conversion.
	var b []byte
	bh := (*reflect.SliceHeader)(unsafe.Pointer(&b))
	sh := (*reflect.StringHeader)(unsafe.Pointer(&s))
	bh.Data = sh.Data
	bh.Len = sh.Len
	bh.Cap = sh.Len
	return Sum64(b)
}

A similar trick can be used in gjson.

[aykevl]

Closing because it is a duplicate.