ponyc: Compile-time crash related to Pony-specific optimization passes

I’m new to both Pony and to programming in general, so I apologize in advance if this is some obvious error on my part.

I was trying to experiment with ponyc to learn more about the language constructs and what expressions typecheck. In so doing I think I managed to crash the compiler. Here is the code I was using on Fedora Linux with ponyc 0.42.0:

// act -- Counter as an actor

actor Counter
  var _count : U32

  new create() =>
    _count = 0

  be inc() =>
    _count = _count + 1
  
  be display(out : OutStream) =>
    out.print(_count.string())
    _count = 0
  
primitive Math  
  fun add(x : U64, y : U64): U64 =>
    x + y
  fun subtract(x : U64, y : U64): U64 =>
    x - y

actor Main
  new create(env : Env) =>
    let c = Counter
    c.inc()
    c.display(env.out)
    for animal in ["lions"; "tigers"; "bears"].values() do
      env.out.print(animal)
    end

And here is the error text this provoked in bash:

[zack@localhost act]$ ponyc
Building builtin -> /home/zack/.local/share/ponyup/ponyc-release-0.42.0-x86_64-linux-gnu/packages/builtin
Building . -> /home/zack/projs/act
Generating
 Reachability
 Selector painting
 Data prototypes
 Data types
 Function prototypes
 Functions
 Descriptors
Optimising
/tmp/cirrus-ci-build/src/libponyc/codegen/genopt.cc:1236: makeMsgChains: Assertion `prev_msg == (*iter)->getArgOperand(3)` failed.

Backtrace:
  ponyc(ponyint_assert_fail+0x82) [0x762c12]
  ponyc(_ZN16MergeMessageSend13makeMsgChainsERKN4llvm11SmallVectorIPNS0_8CallInstELj16EEE+0x269) [0x6dff89]
  ponyc(_ZN16MergeMessageSend15runOnBasicBlockERN4llvm10BasicBlockE+0x206) [0x6df4c6]
  ponyc() [0x883207]
  ponyc(_ZN4llvm13FPPassManager13runOnFunctionERNS_8FunctionE+0x44e) [0x87e77e]
  ponyc() [0x1123cb1]
  ponyc(_ZN4llvm6legacy15PassManagerImpl3runERNS_6ModuleE+0x53a) [0x87f05a]
  ponyc(genopt+0x4c3) [0x6d9c93]
  ponyc(genexe+0x218) [0x6c46a8]
  ponyc(codegen+0xad) [0x6bc1fd]
  ponyc(main+0x187) [0x6b1b07]
  /lib64/libc.so.6(__libc_start_main+0xd5) [0x7f3829f6fb75]
  ponyc(_start+0x2e) [0x6b18be]
This is an optimised version of ponyc: the backtrace may be imprecise or incorrect.
Use a debug version to get more meaningful information.
Stack dump:
0.      Running pass 'CallGraph Pass Manager' on module 'act'.
1.      Running pass 'BasicBlock Pass Manager' on function '@Main_Dispatch'
2.      Running pass 'Group message sends in the same BasicBlock' on basic block '%Main_tag_create_oo.exit'
Aborted (core dumped)
[zack@localhost act]$

What seems to have provoked it were the three lines at the bottom with the iterator. If I comment them out – or if I comment out the three lines immediately above them – it compiles and runs normally. I confess that I don’t even know if I inadvertently wrote invalid code, but I would have expected some sort of syntax or type error rather than what looks like a dump from LLVM.

Please let me know if I should include other information.

About this issue

Original URL
State: closed
Created 3 years ago
Comments: 22 (22 by maintainers)

Commits related to this issue

Fix a compile-time crash related to Pony-specific optimizations. Ticket #3784 tracked an issue related the MergeMessageSend optimization pass, which does Pony-specific optimizations within the LLVM o... — committed to ponylang/ponyc by jemc 3 years ago
Fix a compile-time crash related to Pony-specific optimizations. Ticket #3784 tracked an issue related the MergeMessageSend optimization pass, which does Pony-specific optimizations within the LLVM o... — committed to ponylang/ponyc by jemc 3 years ago

Most upvoted comments

Last observation:

If you take this slightly different code-> It crashes.

actor A
  be a() =>
    None

actor B
  be b(str: String) =>
    None

actor Main
  new create(e: Env) =>
    let b = B
    let a = A
    a.a()

    for x in ["a"].values() do
      b.b(x)
    end

However, if you switch the order of the let a and let b it doesn’t:

actor A
  be a() =>
    None

actor B
  be b(str: String) =>
    None

actor Main
  new create(e: Env) =>
    let a = A
    let b = B
    a.a()

    for x in ["a"].values() do
      b.b(x)
    end

redvers on Jul 8, 2021