gccgo: cannot convert user-defined type whose underlying type is uintptr to unsafe.Pointer

[h4ck3rm1k3]

This example from the go core runtime , trying to compile with

unsafe_pointer.go:13:21: error: invalid type conversion (cannot use type gclinkptr as type unsafe.Pointer)
  x := unsafe.Pointer(v)

package main
import  "unsafe"
import  "fmt"
type gclinkptr uintptr
type mspan struct {
        freelist gclinkptr // list of free objects                                                                                                                
}

func main() {
    var a mspan 
    var s *mspan
    s = &a
        v := s.freelist
        x := unsafe.Pointer(v)
    fmt.Println(x)
}

See code here on play :
http://play.golang.org/p/HkMAa-VU0x

[bradfitz]

/cc @ianlancetaylor for gccgo

[h4ck3rm1k3]

see a mention of something similar conformal/gotk3#58 (comment)

[h4ck3rm1k3]

strange, this works
it looks like the type is not begin resolved.

package main
import"unsafe"
import"fmt"
type mspan struct {
        freelist uintptr // list of free objects                                                                                                                  
}
func main() {
        var a mspan
        var s *mspan
        s = &a
        v := s.freelist
        x := unsafe.Pointer(v)
        fmt.Println(x)
}

[minux]

gccgo implements the conversion to unsafe.Pointer wrong (or based on a previous version of the spec?) The spec says: "Any pointer or value of underlying type uintptr can be converted to a Pointer type and vice versa." however, gccgo only allows conversion to unsafe.Pointer if the type is uintptr. Simple reproduction: package f import "unsafe" type T uintptr var x unsafe.Pointer = unsafe.Pointer(T(0))

[ianlancetaylor]

Fixed on tip.