ANSITerm makes the compiler crash

[pandaman64]

I'm trying to implement a twitter client with Pony, and I want to take in user inputs to tweet it.
So I was trying ANSITerm to read a line from the keyboard, but the compiler crashed during code generation when I introduced it.

Here is the minimal code of the crash:
https://github.com/pandaman64/pony-twitter/blob/c0076ef0e507c895b6abf87a60d3425dbf3758c5/src.pony

Expected result: it compiles
Actual result: the compiler crashes during code generation

If you comment out the last line, the compiler will not crash.
Note that try..end before Readline is necessary to reproduce the bug. If you remove them, the program successfully compiles.

ponyc -v shows

0.15.0-6b066b0 [debug]
compiled with: llvm 3.9.1 -- cc (Ubuntu 5.4.0-6ubuntu1~16.04.4) 5.4.0 20160609

and my ponyc runs on Ubuntu 16.04.2 LTS on Windows (I'm using Bash on Ubuntu on Windows).
The crash also happens when I ran ponyc of this version:

0.15.0-321b7c6 [debug]
compiled with: llvm 3.8.0 -- cc (Ubuntu 5.4.0-6ubuntu1~16.04.4) 5.4.0 20160609

on Ubuntu 16.04.1 LTS on VMWare.

Thanks,

[pandaman64]

Here is the compiler log:
https://pastebin.com/ksNwyfQA

[SeanTAllen]

@pandaman64 I can't reproduce the crash with your minimal example. You appear to have provided the version I gave to you that fixes the problem. Can you verify that is the case?

[SeanTAllen]

Ok, this crashes for me locally on OSX. @pandaman64 what platform are you using? What LLVM?

[SeanTAllen]

This is odd...

use "net/http"
use "term"
use "promises"

class Notify
    fun ref apply(line: String, prompt: Promise[String]) =>
        prompt(line)
    fun ref tab(line: String): Seq[String] box => Array[String]

class SessionHandler
                fun tag apply(session: HTTPSession tag): HTTPHandler =>
                    object ref is HTTPHandler end
actor Main
    new create(env: Env) =>
        try
            let client = HTTPClient(env.root as AmbientAuth, None)
            let url = URL.build("")?
            let handler = SessionHandler
            let request = Payload.request("", url)
            client(consume request, consume handler)?
        end

        let readline = Readline(Notify, env.out)
        let terminal = ANSITerm(consume readline, env.input)

commenting out either

let terminal = ANSITerm(consume readline, env.input)

or

client(consume request, consume handler)?

makes it compile for me

[SeanTAllen]

backtrace:

* thread #1: tid = 0x71b66, 0x00007fff99300f06 libsystem_kernel.dylib`__pthread_kill + 10, queue = 'com.apple.main-thread', stop reason = signal SIGABRT
    frame #0: 0x00007fff99300f06 libsystem_kernel.dylib`__pthread_kill + 10
libsystem_kernel.dylib`__pthread_kill:
->  0x7fff99300f06 <+10>: jae    0x7fff99300f10            ; <+20>
    0x7fff99300f08 <+12>: movq   %rax, %rdi
    0x7fff99300f0b <+15>: jmp    0x7fff992fb7cd            ; cerror_nocancel
    0x7fff99300f10 <+20>: retq
(lldb) bt
* thread #1: tid = 0x71b66, 0x00007fff99300f06 libsystem_kernel.dylib`__pthread_kill + 10, queue = 'com.apple.main-thread', stop reason = signal SIGABRT
  * frame #0: 0x00007fff99300f06 libsystem_kernel.dylib`__pthread_kill + 10
    frame #1: 0x00007fff93c4a4ec libsystem_pthread.dylib`pthread_kill + 90
    frame #2: 0x00007fff98c166df libsystem_c.dylib`abort + 129
    frame #3: 0x00000001000fb2a3 ponyc`ponyint_assert_fail(expr="t != NULL", file="src/libponyc/codegen/genbox.c", line=16, func="gen_box") + 403 at ponyassert.c:60
    frame #4: 0x000000010003cfa6 ponyc`gen_box(c=0x00007fff5fbff250, type=0x000000011c27e7c0, value=0x000000011e11c950) + 134 at genbox.c:16
    frame #5: 0x000000010004af5d ponyc`gen_assign_cast(c=0x00007fff5fbff250, l_type=0x000000010c009840, r_value=0x000000011e11c950, type=0x000000011c27e7c0) + 381 at genexpr.c:285
    frame #6: 0x000000010004c38e ponyc`genfun_forward(c=0x00007fff5fbff250, t=0x000000011c274800, n=0x000000011bcab280, m=0x0000000117e50080) + 622 at genfun.c:684
    frame #7: 0x000000010004bfbf ponyc`genfun_method_bodies(c=0x00007fff5fbff250, t=0x000000011c274800) + 191 at genfun.c:844
    frame #8: 0x000000010007a573 ponyc`gentypes(c=0x00007fff5fbff250) + 979 at gentype.c:862
    frame #9: 0x0000000100049fe8 ponyc`genexe(c=0x00007fff5fbff250, program=0x000000010b7bfd40) + 504 at genexe.c:408
    frame #10: 0x0000000100039a32 ponyc`codegen(program=0x000000010b7bfd40, opt=0x00007fff5fbff758) + 274 at codegen.c:1028
    frame #11: 0x00000001000a8773 ponyc`generate_passes(program=0x000000010b7bfd40, options=0x00007fff5fbff758) + 51 at pass.c:301
    frame #12: 0x0000000100002701 ponyc`compile_package(path=".", opt=0x00007fff5fbff758, print_program_ast=false, print_package_ast=false) + 161 at main.c:249
    frame #13: 0x00000001000024c0 ponyc`main(argc=1, argv=0x00007fff5fbff808) + 1120 at main.c:374
    frame #14: 0x00007fff93ae45ad libdyld.dylib`start + 1
    frame #15: 0x00007fff93ae45ad libdyld.dylib`start + 1

[pandaman64]

I'm using llvm 3.9 provided by apt.
Yeah, that's weird that we need lines before readline, and even replacing client(consume request, consume handler)? with env.out.print("") makes it compile!

[jemc]

Pinging @Praetonus, as this involves gen_box, and he has spent a lot of time there recently.

@SeanTAllen the odd behaviour you're noting is likely because the crash happens after the reach pass, so it has some dependence on which types or methods are reachable - commenting out one or the other line is making some relevant types become unreachable by the program.

[Praetonus]

I've found the problem. It's trivial, I'll make a PR ASAP.

[SeanTAllen]

@pandaman64 this should be fixed on master.

[pandaman64]

It compiles! Thanks!