REPL: piped input causes infinite loop

[michaelficarra]

cat myInputFile | location/to/bin/rebl

The above causes the REPL to go into an infinite loop as it exits except when the input file contains an actual "end of transmission" character (ascii code 4). I believe it has something to do with trying to exit while Readline::readline is waiting for input. I've tried to fix it a number of ways so far and failed.

• Tried writing an end of transmission or newline character to $stdin so that Readline::readline could read it off, but it fails because $stdin is opened as read-only. Can't reopen $stdin as read-write.
• Tried finding the child process that Readline::readline is using because killing that successfully exits the REPL. No luck, there's no cross-platform way to find child processes.
• Looked into creating a writeable proxy IO object that Readline::readline will read from so we can forward $stdin and also write to it, but there's no declarative or event-driven way to forward $stdin to the proxy IO object.

[jhellerstein]

Any insight as to whether there's something unusual in REBL here? This sounds like a generic issue with Readline::readline to be worked around/with. If that's so, perhaps we can isolate a little 5-line example program that illustrates/isolates the problem?

[michaelficarra]

It certainly could be a generic Readline::readline issue. I can easily reproduce #151 using Readline::readline in irb, but after trying for 15 minutes or so, I can't reproduce this issue in irb. I don't think REBL is doing anything particularly out of the ordinary here, though. I tried adding logging output in the vicinity of the loop construct and didn't see any output, but I don't think that's a trustworthy result since the program is already in a partially-exited state (which may no longer be able to output to stdout) when it goes into its infinite loop.