Segfault (from gc.c) when matching on union of (A iso | B val) #4807
Description
This is loosely based on the match#implicit-matching-on-capabilities-in-the-context-of-union-types example from the tutorial
Code to reproduce
class A
var v: Any val
new create(v': Any val) =>
v = consume v'
class B
actor Foo
var _x: (A iso | B val | None)
let e: Env
new create(e': Env, x': (A iso | B val | None)) => // the B val is essential. If we remove it, the segfault does not occur
e = e'
_x = consume x'
be f() =>
match (_x = None)
| let a: A iso => None
end
actor Main
new create(env: Env) =>
let f_iso = Foo(env, recover A("hello".string()) end)
// Can also use U32(123), Bool(true), etc.
// note that a string without `.string()` doesn't trigger the segfault
f_iso.f()Backtrace
* thread #16, stop reason = EXC_BAD_ACCESS (code=1, address=0x8)
frame #0: 0x0000000100012330 28_gc773_segfault`ponyint_gc_release(gc=0x00000001081788d8, aref=0x000000014817bc00) at gc.c:773:5
770 void* p = obj->address;
771 object_t* obj_local = ponyint_objectmap_getobject(&gc->local, p, &index);
772
-> 773 pony_assert(obj_local->rc >= obj->rc);
774 obj_local->rc -= obj->rc;
775 }
776
Target 0: (28_gc773_segfault) stopped.
(lldb) bt
* thread #16, stop reason = EXC_BAD_ACCESS (code=1, address=0x8)
* frame #0: 0x0000000100012330 28_gc773_segfault`ponyint_gc_release(gc=0x00000001081788d8, aref=0x000000014817bc00) at gc.c:773:5
frame #1: 0x0000000100005acc 28_gc773_segfault`handle_message(ctx=0x000000010817b308, actor=0x0000000108178800, msg=0x000000014817b480) at actor.c:357:10
frame #2: 0x000000010000555c 28_gc773_segfault`ponyint_actor_run(ctx=0x000000010817b308, actor=0x0000000108178800, polling=false) at actor.c:561:20
frame #3: 0x0000000100022208 28_gc773_segfault`run(sched=0x000000010817b2c0) at scheduler.c:1255:23
frame #4: 0x0000000100021408 28_gc773_segfault`run_thread(arg=0x000000010817b2c0) at scheduler.c:1308:3
frame #5: 0x000000019c67fbc8 libsystem_pthread.dylib`_pthread_start + 136
Ponyc version
0.60.5-f79c2390 [debug]
Compiled with: LLVM 18.1.8 -- AppleClang-15.0.0.15000309-arm64
Defaults: pic=true