Crash with "fatal error: cgoUse should not be called" when using NkEditStringZeroTerminated

[Wolfgang Faust]

Full test case here: https://gist.github.com/wolfgang42/07e8a2677c7f6e36393bdca862bebac2

From reading runtime/cgo.go it looks like somehow the nuklear bindings have gotten into some kind of can't happen state, but I don't know enough about how any of this works to be able to figure out how this could happen.

[alexniver]

i got the same problem

[alexniver]

from golang source code :
https://github.com/golang/go/blob/master/src/runtime/cgo.go

// cgoUse is called by cgo-generated code (using go:linkname to get at
// an unexported name). The calls serve two purposes:
// 1) they are opaque to escape analysis, so the argument is considered to
// escape to the heap.
// 2) they keep the argument alive until the call site; the call is emitted after
// the end of the (presumed) use of the argument by C.
// cgoUse should not actually be called (see cgoAlwaysFalse).
func cgoUse(interface{}) { throw("cgoUse should not be called") }

[alexniver]

I find the problem.

var textMaxLen = int32(64)
var textBuf = []byte{}
var textBufLen = int32(0)

if use var textBuf = []byte{}, this will cause textBuf change to a new ref in memory. to sovle this, use code below.

var textMaxLen = int32(64)
var textBuf = make([]byte, textMaxLen)
var textBufLen = int32(0)

[Max Kupriianov]

@alexniver thank you for this solution! I never encountered it, because I always use the make() pattern. Also, it's a rule of thumb to only use pre-allocated memory, because C cannot allocate memory inside go structures. You must either allocate on Go side (using make) or on C side (malloc).

Thank you for looking into this.