Fix a hang where ctrl-d can hang the next call to Readline#222
Open
tpodowd wants to merge 1 commit into
Open
Conversation
When running the examples/readline-demo, you can enter the `sleep` command which causes the loop to sleep for 4 seconds before it calls Readline() again. If you press ctrl-d during the sleep, the program will hang. Normally ctrl-d is mapped to CharDelete (rune:4), however termios manpage states that when not in raw mode the following is true: > VEOF (004, EOT, Ctrl-D) End-of-file character (EOF). More > precisely: this character causes the pending tty buffer to be sent > to the waiting user program without waiting for end-of-line. If > it is the first character of the line, the read(2) in the user > program returns 0, which signifies end-of-file. Recognized > when ICANON is set, and then not passed as input. Between calls to Readline, the terminal is not in raw mode and thus read returns 0. Note that err=io.EOF is correctly unset. Previously the terminal ioloop returned the 0 on the t.outchan which is being read by the operation ioloop. Unfortunately, 0 is also used to indicate EOF and thus the operation ioloop terminates which means that nobody will read from t.outchan any more and thus input processing stops and causes the hang. The fix is simply to ignore 0 in the terminal and go on expecting characters.
This file contains hidden or bidirectional Unicode text that may be interpreted or compiled differently than what appears below. To review, open the file in an editor that reveals hidden Unicode characters.
Learn more about bidirectional Unicode characters
Sign up for free
to join this conversation on GitHub.
Already have an account?
Sign in to comment
1 participant
Add this suggestion to a batch that can be applied as a single commit.This suggestion is invalid because no changes were made to the code.Suggestions cannot be applied while the pull request is closed.Suggestions cannot be applied while viewing a subset of changes.Only one suggestion per line can be applied in a batch.Add this suggestion to a batch that can be applied as a single commit.Applying suggestions on deleted lines is not supported.You must change the existing code in this line in order to create a valid suggestion.Outdated suggestions cannot be applied.This suggestion has been applied or marked resolved.Suggestions cannot be applied from pending reviews.Suggestions cannot be applied on multi-line comments.Suggestions cannot be applied while the pull request is queued to merge.Suggestion cannot be applied right now. Please check back later.
When running the examples/readline-demo, you can enter the
sleepcommand which causes the loop to sleep for 4 seconds before it calls Readline() again. If you press ctrl-d during the sleep, the program will hang.Normally ctrl-d is mapped to CharDelete (rune:4), however termios manpage states that when not in raw mode the following is true:
Between calls to Readline, the terminal is not in raw mode and thus read returns 0. Note that err=io.EOF is correctly unset.
Previously the terminal ioloop returned the 0 on the t.outchan which is being read by the operation ioloop. Unfortunately, 0 is also used to indicate EOF and thus the operation ioloop terminates which means that nobody will read from t.outchan any more and thus input processing stops and causes the hang.
The fix is simply to ignore 0 in the terminal and go on expecting characters.