In genBox your code is saying that val contains a pointer to interface{}. In
other words its an interface{} that contains a *interface{}. That is a weird
but valid construct.
I suggest you dereference it and see what the contained interface holds.
Something like:
valDeref := val.(*interface{})
fmt.Printf("val contains=%T", valDeref)
You may find that valDeref contains the *int64 you are looking for.
As an aside, *interface{} is usually an indication that someone somewhere is
passing the wrong value to the function since it almost never makes sense to
pass a pointer to interface{}.
On Mon, 11 Jan 2021, at 4:03 PM, Steve Murphy wrote:
> Hello!
>
> I keep getting:
> panic: interface conversion: interface {} is *interface {}, not *int64
> [recovered]
> panic: interface conversion: interface {} is *interface {}, not *int64
>
> I *suspect* what is happening is that the KDElem struct has an item field
> whose
> type is interface{}, so that you can store a pointer to some struct (of your
> own making),
> or an index into an array of structs, or... *whatever*, but in my case, it's
> an index into an array
> of objects. The itemfunc (or genBox in my test code) is supposed to set the
> item field in
> the KDElem struct to the proper index, as the struct has just been created,
> and the job
> of the itemfunc is to make it point to the right object, and set the bounds
> info in the new struct.
>
> type KdElem struct {
> item interface{} // a ptr to a particular struct, or an index into
> an array of objects, or....
> ...
> }
>
> And the func that calls the itemfunc (genBox) looks like this:
>
> func loadItems(itemfunc func(arg interface{}, val interface{}, size *KdBox)
> int, arg interface{}, extent KdBox, length *int64, mean *float64) *KdElem {
> ...
> newItem = new(KdElem)
> if itemfunc(arg, &newItem.item, newItem.size) != 0 {
> ...
>
>
> And, in this case the itemfunc declaration looks like this:
>
> func genBox(arg interface{}, val interface{}, box *KdBox) int {
> var offsetp = arg.(*int64) // successful
> var offset = *offsetp // successful
> // fmt.Printf("genBox: offset=%v offsetp=%v\n", offset, offsetp)
> fmt.Printf("genBox: arg type=%T argval=%v, val type=%T, val
> val=%v\n", arg, arg, val, val)
> if offset < KDBoxes {
> fmt.Printf("genBox: val=%v *int64=%v\n", val, val)
> var realval *int64 = val.(*int64) // <<-- This is line 43!
> Compiles.... but... Crash!!!
> *realval = offset + 1
> ...
>
> Now, I get this from a go test:
>
> KdBuild: arg type=*int64 argval=0xc0000d2078;
> genBox: arg type=*int64 argval=0xc0000d2078, val type=*interface {}, val
> val=0xc0000ba640
> genBox: val=0xc0000ba640 *int64=0xc0000ba640
> --- FAIL: TestKd1 (0.08s)
> panic: interface conversion: interface {} is *interface {}, not *int64
> [recovered]
> panic: interface conversion: interface {} is *interface {}, not *int64
>
> goroutine 19 [running]:
> testing.tRunner.func1(0xc000108100)
> /usr/lib/go-1.13/src/testing/testing.go:874 +0x3a3
> panic(0x523360, 0xc0000c2360)
> /usr/lib/go-1.13/src/runtime/panic.go:679 +0x1b2
> parsetree.com/kdtree.genBox(0x50eec0, 0xc0000d2078, 0x50ef40, 0xc0000ba640,
> 0x0, 0x0)
> /home/murf/go/kdtree/kdtree1_test.go:43 +0x270
> parsetree.com/kdtree.loadItems(0x5570f8, 0x50eec0, 0xc0000d2078,
> 0x7fffffffffffffff, 0x7fffffffffffffff, 0x8000000000000000,
> 0x8000000000000000, 0xc00096ab38, 0xc00096ab30, 0x0)
> /home/murf/go/kdtree/kdtree.go:683 +0xec
> parsetree.com/kdtree.KdBuild(0x5570f8, 0x50eec0, 0xc0000d2078, 0x0)
> /home/murf/go/kdtree/kdtree.go:168 +0x17e
> parsetree.com/kdtree.TestKd1(0xc000108100)
> /home/murf/go/kdtree/kdtree1_test.go:72 +0x13a
> testing.tRunner(0xc000108100, 0x5570f0)
> /usr/lib/go-1.13/src/testing/testing.go:909 +0
>
> How do I set realval to the (*int64) value that's in val?
>
> murf
>
>
> --
>
> Steve Murphy
> ParseTree Corporation
> 57 Lane 17
> Cody, WY 82414
> ✉ murf at parsetree dot com
> ☎ 307-899-0510
>
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