Exception#backtrace? raises an IndexError on macOS

[marksiemers]

I have not yet been able to successfully reduce the code. The relevant code is:

      begin
        message = @ex.inspect_with_backtrace
      rescue ex : IndexError
        # ERROR: Any of these will cause another IndexError (at least on macOS)
        # ex.inspect_with_backtrace # or @ex.inspect_with_backtrace
        # ex.backtrace? # or @ex.backtrace?
        message = @ex.message
      end

To reproduce, using macOS, you can follow these steps:

1. git clone git@github.com:amberframework/amber.git
2. git fetch && git checkout ms/fix-internal_server_error-error
3. Uncomment the line at src/amber/controller/error.cr:35 (or line 36): https://github.com/amberframework/amber/pull/625/files#diff-fefe72c37ea251ccaec8417bffb49e8cR35
4. Run crystal spec spec/amber/router/pipe/error_spec.cr:15

With the line commented out, the tests pass:

$ crystal spec spec/amber/router/pipe/error_spec.cr:15
.....

Finished in 128.61 milliseconds
5 examples, 0 failures, 0 errors, 0 pending

With the line uncommented, we get the Index out of bounds error.

$ crystal spec spec/amber/router/pipe/error_spec.cr:15
....E

Failures:

  1) Amber::Pipe::Error returns status code 500 for all other exceptions

       Index out of bounds

$ crystal -v
Crystal 0.24.1 (2018-01-27)
LLVM: 5.0.1
Default target: x86_64-apple-macosx

$ sw_vers
ProductName:	Mac OS X
ProductVersion:	10.13.3
BuildVersion:	17D47

From what I've looked at in the crystal code base, it may have to do with CallStack. There is a difference in darwin vs linux in that file:

crystal/src/callstack.cr

Line 8 in 3515968

{% if flag?(:darwin) %}

What led me there is:
https://github.com/crystal-lang/crystal/blob/v0.24.1/src/exception.cr#L35

And then here:

crystal/src/callstack.cr

Line 157 in 3515968

private def decode_backtrace

[ysbaddaden]

Does it still happen with crystal master? I fixed a very similar issue recently.

[marksiemers]

I'm checking now. Is this the relevant commit: 048f77e

[asterite]

Probably duplicate of #5224

[marksiemers]

I'm running into an unrelated issue when trying to test against master, may just need to update some dependencies (pg).

It is a JSON::Type error - that was updated to JSON::Any, correct?

[marksiemers]

This is fixed in master.

Sorry it took me a while to get setup - there are a handful of breaking changes that affect crystal-pg and amber that I had to work through.