PTY leak when Cling runs for an extended period

[mono0x]

When running Cling for an extended duration (approximately several days), the number of PTYs gradually increases. If the number of PTYs reaches the system limit, Cling loses search functionality, and other terminal apps cannot be opened.

Terminating Cling immediately restores the number of PTYs to normal. Then restarting Cling afterward restores full functionality.

However, this issue has only been observed on one of my two Mac machines. I have not yet identified the exact conditions under which this occurs. I will update you on this issue once I have more details.

Below is an example of the PTY count before and after terminating Cling:

❯ ls /dev/ttys* | wc -l
527

❯ ls /dev/ttys* | wc -l
19

I am using Cling 1.2.1 on macOS Sequoia 15.4.

[alin23]

Yep, got this too once, it's related to the fzf process not being able to start and the current logic restarts indefinitely creating a new PTY. Not sure why the old PTY doesn't get deallocated.

Thanks for confirming it wasn't just a fluke, I'll look into it.

[Acelya-9028]

Ahahah LOL Thank you very much!!

I was getting a lot of [forkpty: Resource temporarily unavailable][Could not create a new process and open a pseudo-tty.] errors and was wondering where this could be coming from.

# State: Cling search doesn't work
Fig@MacBookPro ~ % ls /dev/ttys* | wc -l
     527
Fig@MacBookPro ~ % sysctl kern.tty.ptmx_max
kern.tty.ptmx_max: 511

Fig@MacBookPro ~ % sudo sysctl -w kern.tty.ptmx_max=768
kern.tty.ptmx_max: 511 -> 768
# State: Cling search works now!!

# I quit Cling
Fig@MacBookPro ~ % ls /dev/ttys* | wc -l
      17

# OMG xD

[alin23]

Ahahah LOL Thank you very much!!

I was getting a lot of [forkpty: Resource temporarily unavailable][Could not create a new process and open a pseudo-tty.] errors and was wondering where this could be coming from.

State: Cling search doesn't work

Fig@MacBookPro ~ % ls /dev/ttys* | wc -l
527
Fig@MacBookPro ~ % sysctl kern.tty.ptmx_max
kern.tty.ptmx_max: 511

Fig@MacBookPro ~ % sudo sysctl -w kern.tty.ptmx_max=768
kern.tty.ptmx_max: 511 -> 768

State: Cling search works now!!

I quit Cling

Fig@MacBookPro ~ % ls /dev/ttys* | wc -l
17

OMG xD

Yeah, I still can't find the culprit though. The PTY should be deallocated by the system automatically when I close the file descriptors for stdin and stdout but maybe they get leaked in the FZF process and that's what causes it.

I'm still looking for a workaround, but it might be possible that I'll have to write my own search algorithm and avoid the fzf in PTY thingie.

[alin23]

A workaround was released in v1.2.2 by restarting the app periodically, every 12 hours, when it's in the background.

I know it's low tech, but it does fix the solution until I can find what causes this, or redo the search logic entirely without fzf.

[mono0x]

Thank you for implementing the workaround! Let me try the latest version.