Segfault

[SeanTAllen]

I haven't fully worked the why of this segfault:

Process 81526 stopped
* thread #2: tid = 0x568fa6, 0x0000000100072ed2 wallaroo`ponyint_messageq_push(q=0x00000001198f20c8, m=0x00000001198f27a0) + 82 at messageq.c:75, stop reason = EXC_BAD_ACCESS (code=1, address=0x8)
   frame #0: 0x0000000100072ed2 wallaroo`ponyint_messageq_push(q=0x00000001198f20c8, m=0x00000001198f27a0) + 82 at messageq.c:75
  72      #ifdef USE_VALGRIND
  73        ANNOTATE_HAPPENS_BEFORE(&prev->next);
  74      #endif
-> 75        atomic_store_explicit(&prev->next, m, memory_order_release);
  76
  77        return was_empty;
  78      }

Minimal case:

CRASHES:

use "ponytest"

trait tag Taggable
  be foo[In: Any val](i: In)

trait tag CFConsumer
  be bar() => None

type Consumer is CFConsumer

type TagableConsumer is (Taggable & Consumer)

class MockTaggable is TagableConsumer
  fun tag foo[In: Any val](i: In) =>
    this

  fun tag bar() =>
    this

primitive _X
  fun send[In: Any val](d: In, e: TagableConsumer) =>
    e.foo[In](d)

actor Main is TestList
  new create(env: Env) =>
    PonyTest(env, this)

  new make() =>
    None

  fun tag tests(test: PonyTest) =>
    test(_Test)

class iso _Test is UnitTest
  fun name(): String =>
    "test"

  fun apply(h: TestHelper) =>
    let tc = MockTaggable

    _X.send[ISize](ISize(10), tc)

Changing class MockTaggable to actor MockTaggable fixes the segfault and the test runs to completion.

Not calling tc.foo from inside the primitive also takes care of the issue:

DOESN'T CRASH:

use "ponytest"

trait tag Taggable
  be foo[In: Any val](i: In)

trait tag CFConsumer
  be bar() => None

type Consumer is CFConsumer

type TagableConsumer is (Taggable & Consumer)

actor MockTaggable is TagableConsumer
  fun tag foo[In: Any val](i: In) =>
    this

  fun tag bar() =>
    this

actor Main is TestList
  new create(env: Env) =>
    PonyTest(env, this)

  new make() =>
    None

  fun tag tests(test: PonyTest) =>
    test(_Test)

class iso _Test is UnitTest
  fun name(): String =>
    "test"

  fun apply(h: TestHelper) =>
    let tc = MockTaggable

    tc.foo[ISize](ISize(10))

[Praetonus]

In the reachability data structure in the compiler, MockTaggable isn't in the subtype list of (Taggable & Consumer) (the DS is reach_type_t.subtypes). Then, the behaviour_in_every_subtype function doesn't see MockTaggable and treats the method call as a message send. I think that's a problem with the subtype assignment during the reachability pass.

[Praetonus]

There seem to be a workaround for the problem, you can make TaggableConsumer a trait instead of a type alias.

[Praetonus]

After looking into it, unions and intersections aren't picking up their subtypes during the reachability analysis.