From @masak

<BenGoldberg> r​: my $a ($b, $c); $b = 42; say $b
<camelia> rakudo-parrot 3cef56​: OUTPUT«(signal SEGV)»
<camelia> ..rakudo-jvm 882e33​: OUTPUT«java.lang.NullPointerException [...]
<masak> whoa.
* masak submits rakudobug
<masak> r​: my $a ($b, $c); $b = 42
<camelia> rakudo-jvm 882e33​: OUTPUT«java.lang.NullPointerException [...]
<camelia> ..rakudo-parrot 3cef56​: OUTPUT«(signal SEGV)»
<jnthn> I'm surprised it even parses; I must be misremembering
something in the grammar...
<TimToady> it's just coming in as a postconstraint
<jnthn> oh...
<jnthn> I suspect we don't try to handle that code path at all :)
<jnthn> So heck knows what comes of the $b and $c... :)
<TimToady> r​: my $a where 42; $a = 43
<camelia> rakudo-parrot 3cef56, rakudo-jvm 882e33​: ( no output )
<TimToady> yeah

From @usev6

Status update​: Right now this is no longer a Null PMC access error on Parrot but we get a segfault on Moar as well​:

$ perl6-m -e 'my $a ($b, $c); $b = 42;'
Segmentation fault

$ perl6-p -e 'my $a ($b, $c); $b = 42;'
Cannot assign to an immutable value
  in block <unit> at -e​:1

$ perl6-j -e 'my $a ($b, $c); $b = 42;'
java.lang.NullPointerException
  in block <unit> at -e​:1

@usev6 - Status changed from 'new' to 'open'

From @nwc10

On Fri, Oct 17, 2014 at 03​:08​:12AM -0700, Christian Bartolomaeus via RT wrote​:

Status update​: Right now this is no longer a Null PMC access error on Parrot but we get a segfault on Moar as well​:

$ perl6-m -e 'my $a ($b, $c); $b = 42;'
Segmentation fault

valgrind doesn't spot any undefined behaviour leading up to the SEGV​:

==2246== Invalid read of size 8
==2246== at 0x4F57A5E​: MVM_interp_run (interp.c​:1226)
==2246== by 0x502FBA3​: MVM_vm_run_file (moar.c​:208)
==2246== by 0x40110D​: main (main.c​:191)
==2246== Address 0x10 is not stack'd, malloc'd or (recently) free'd
==2246==
==2246==
==2246== Process terminating with default action of signal 11 (SIGSEGV)​: dumping core
==2246== Access not within mapped region at address 0x10
==2246== at 0x4F57A5E​: MVM_interp_run (interp.c​:1226)
==2246== by 0x502FBA3​: MVM_vm_run_file (moar.c​:208)
==2246== by 0x40110D​: main (main.c​:191)

It's this code (with line numbers)​:

  1223 OP(assign)​: {
  1224 MVMObject *cont = GET_REG(cur_op, 0).o;
  1225 MVMObject *obj = GET_REG(cur_op, 2).o;
  1226 const MVMContainerSpec *spec = STABLE(cont)->container_spec;
  1227 cur_op += 4;
  1228 if (spec) {
  1229 spec->store(tc, cont, obj);
  1230 } else {
  1231 MVM_exception_throw_adhoc(tc, "Cannot assign to an immutable value");
  1232 }
  1233 goto NEXT;

I can't convince gdb to "like" the various local libraries on this machine
(local updated compiler toolchain, but not debugger), so I can't verify which
pointer is NULL.

Nicholas Clark

From @donaldh

2015.02 gives this result on both Moar and JVM​:

my $a ($b, $c); $b = 42; say $b
===SORRY!=== Error while compiling <unknown file>
Post-constraints on variables not yet implemented. Sorry.
at <unknown file>​:1
------> my $a ($b, $c)⏏; $b = 42; say $b
  expecting any of​:
  constraint

This ticket can probably be closed.

From @usev6

I added a test to S04-declarations/my.t with commit Raku/roast@25f2964446

It only tests that there is no NullPointerException (or no segfault which would abort the test) -- everything else passes.

I'm closing this ticket as 'resolved'.

@usev6 - Status changed from 'open' to 'resolved'