Can confirm this is still current behaviour with Rakudo 2019. I have came
across exactly the same issue and found this ticket. I've noticed, If I change
the example to catch exceptions. It then runs:
sub start-element($, $elem, $attr)
{
say "open $elem".indent($depth * 4);
say $attr.elems;
++$depth;
CATCH { default { warn "whoops: $_" } }
}
Produces:
open calendar
whoops: Don't know how many elements a C array returned from a library
in block at /tmp/tst.p6 line 27
open advent
whoops: Don't know how many elements a C array returned from a library
in block at /tmp/tst.p6 line 27
...etc
Underlying issue seems to be that any uncaught exception in a NativeCall Perl
callback currently results in a unfriendly NativeCall MoarVM panic. The
exception itself is lost.
On Tue, 27 Jun 2017 05:59:08 -0700, vladimir.ma...@oracle.com wrote:
> I took the NativeCall sample from here:
>
> https://perl6advent.wordpress.com/2015/12/21/day-21-nativecall-backs-
> and-beyond-c/
>
> --------------------------------------------------------------------------------
> use NativeCall;
>
> sub XML_SetElementHandler(OpaquePointer $parser,
> &start (OpaquePointer, Str, CArray[Str]),
> &end (OpaquePointer, Str))
> is native('expat') { ... }
>
> sub XML_ParserCreate(Str --> OpaquePointer) is
> native('expat') { ... }
> sub XML_ParserFree(OpaquePointer) is
> native('expat') { ... }
> sub XML_Parse(OpaquePointer, Buf, int32, int32 --> int32) is
> native('expat') { ... }
>
> my $xml = q:to/XML/;
> <calendar>
> <advent day="21">
> <topic title="NativeCall Bits and Pieces"/>
> </advent>
> </calendar>
> XML
>
> my $depth = 0;
>
> sub start-element($, $elem, $attr)
> {
> say "open $elem".indent($depth * 4);
> ++$depth;
> }
>
> sub end-element($, $elem)
> {
> --$depth;
> say "close $elem".indent($depth * 4);
> }
>
> my $parser = XML_ParserCreate('UTF-8');
> XML_SetElementHandler($parser, &start-element, &end-element);
>
> my $buf = $xml.encode('UTF-8');
> XML_Parse($parser, $buf, $buf.elems, 1);
>
> XML_ParserFree($parser);
> --------------------------------------------------------------------------------
>
>
> All works fine, unless I try to use the $attr in start-element
>
> sub start-element($, $elem, $attr)
> {
> say "open $elem".indent($depth * 4);
> say $attr.elems;
> ++$depth;
> }
>
>
> The program then terminates with:
>
> MoarVM panic: Internal error: Unwound entire stack and missed handler
>
>
> I have seen that on Solaris, but Linux has the same issue. In both
> cases
> custom build perl6 using 'rakudobrew build moar' so I suppose latest
> git revision.
>
> Thank you
