Uncaught exception - others.c(440) : Field conflict between null and doctype

[mockey]

I have an old web application that runs on neko (mod_neko with apache to be precise), where a user recently reported the following error after a page request:
Uncaught exception - others.c(440) : Field conflict between null and doctype
Any idea what this could be about?

[ConstNW]

probably multithread access to the field 'doctype'

[mockey]

What would cause this and how could that be avoided?

[ConstNW]

Use thread locks or mutex

[mockey]

I don't use any threads deliberately in my code. Is this done by mod_neko?

[RealyUniqueName]

This looks like a bug in neko vm.
Here's the place where the error is thrown:

neko/vm/others.c

Lines 435 to 441 in f1846a1

	if( fdata != val_null && scmp(val_string(fdata),val_strlen(fdata),oname,(int)(name - oname)) != 0 ) {
	buffer b = alloc_buffer("Field conflict between ");
	val_buffer(b,fdata);
	buffer_append(b," and ");
	buffer_append(b,oname);
	bfailure(b);
	}

[ConstNW]

Yes, it's a code where error message composed.
That function val_id is called to get object's field id in object table by name ('doctype') or insert if it does not exists yet.
In that case field id in object table exists but name check was failed and that why the error occur.
Usually that's happens when threads have concurrent access to the same field.

[mockey]

As I said, I don't use threads in this app. I only use the usual neko web stuff.