[perl #123968] Rakudo on MoarVM segfaults on simple IO::Socket::Async echo server

[via RT]

# New Ticket Created by  Moritz Lenz 
# Please include the string:  [perl #123968]
# in the subject line of all future correspondence about this issue. 
# <URL: https://rt.perl.org/Ticket/Display.html?id=123968 >


THe fllowing program:

use v6;
my $connections = IO::Socket::Async.listen(
    'localhost',
    3333,
);
$connections.tap(-> $conn {
        say "Incoming connection";
        $conn.bytes_supply.tap(
            -> $buf {
                say $buf.decode;
                await $conn.write($buf)
            },
            :done({ $conn.close })
        )
    },
);
$connections.wait;

segfaults reliables when I execute it with perl6 version
2015.02-152-ge7a666c
built on MoarVM version 2015.02-17-g86d0c68 as soon as I feed it some input:

$ echo  "foo" | nc localhost 3333

Running under gdb produces this backtrace:

Program received signal SIGSEGV, Segmentation fault.
[Switching to Thread 0x7ffff33c5700 (LWP 15427)]
0x00007ffff79fc2e1 in uv_write2 () from
/home/moritz/p6/rakudo/install/lib/libmoar.so
(gdb) bt
#0  0x00007ffff79fc2e1 in uv_write2 () from
/home/moritz/p6/rakudo/install/lib/libmoar.so
#1  0x00007ffff79a10f2 in write_setup () from
/home/moritz/p6/rakudo/install/lib/libmoar.so
#2  0x00007ffff7999da0 in idle_handler () from
/home/moritz/p6/rakudo/install/lib/libmoar.so
#3  0x00007ffff79f8b1a in uv.run_idle () from
/home/moritz/p6/rakudo/install/lib/libmoar.so
#4  0x00007ffff79f51ec in uv_run () from
/home/moritz/p6/rakudo/install/lib/libmoar.so
#5  0x00007ffff7999d34 in enter_loop () from
/home/moritz/p6/rakudo/install/lib/libmoar.so
#6  0x00007ffff7986256 in thread_initial_invoke () from
/home/moritz/p6/rakudo/install/lib/libmoar.so
#7  0x00007ffff7969b6d in MVM_interp_run () from
/home/moritz/p6/rakudo/install/lib/libmoar.so
#8  0x00007ffff79862ae in start_thread () from
/home/moritz/p6/rakudo/install/lib/libmoar.so
#9  0x00007ffff79fcd87 in uv.thread_start () from
/home/moritz/p6/rakudo/install/lib/libmoar.so
#10 0x00007ffff6f69182 in start_thread (arg=0x7ffff33c5700) at
pthread_create.c:312
#11 0x00007ffff757f47d in clone () at
../sysdeps/unix/sysv/linux/x86_64/clone.S:111

Running it under gdb prevents the segfault on the first connection, and
on the
second, produces this:

==15474== Thread 3:
==15474== Invalid read of size 4
==15474==    at 0x4FE92E1: uv_write2 (in
/home/moritz/p6/rakudo/install/lib/libmoar.so)
==15474==    by 0x4F8E0F1: write_setup (in
/home/moritz/p6/rakudo/install/lib/libmoar.so)
==15474==    by 0x4F86D9F: idle_handler (in
/home/moritz/p6/rakudo/install/lib/libmoar.so)
==15474==    by 0x4FE5B19: uv__run_idle (in
/home/moritz/p6/rakudo/install/lib/libmoar.so)
==15474==    by 0x4FE21EB: uv_run (in
/home/moritz/p6/rakudo/install/lib/libmoar.so)
==15474==    by 0x4F86D33: enter_loop (in
/home/moritz/p6/rakudo/install/lib/libmoar.so)
==15474==    by 0x4F73255: thread_initial_invoke (in
/home/moritz/p6/rakudo/install/lib/libmoar.so)
==15474==    by 0x4F56B6C: MVM_interp_run (in
/home/moritz/p6/rakudo/install/lib/libmoar.so)
==15474==    by 0x4F732AD: start_thread (in
/home/moritz/p6/rakudo/install/lib/libmoar.so)
==15474==    by 0x4FE9D86: uv__thread_start (in
/home/moritz/p6/rakudo/install/lib/libmoar.so)
==15474==    by 0x5A9A181: start_thread (pthread_create.c:312)
==15474==    by 0x54C147C: clone (clone.S:111)
==15474==  Address 0xb8 is not stack'd, malloc'd or (recently) free'd

before producing a segfault with the same stacktrace as gdb.

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