cat <(node -v) never exits after >= 12.5.0 #28530

Activity

1. JounQin

   changed the title [-]`cat <(node -v)` never exits[/-] [+]`cat <(node -v)` never exits after >= 12.5.0[/+] on Jul 4, 2019
2. bnoordhuis

   added

   confirmed-bugIssues and PRs for confirmed bugs.Issues and PRs for confirmed bugs.

   on Jul 4, 2019
3. bnoordhuis commented on Jul 4, 2019

   

   bnoordhuis

   on Jul 4, 2019

   Last edited by bnoordhuis

   Member

   More actions

   I can reproduce. It's caused by #24260 except not really - the tcsetattr() call (which libc turns into an ioctl()) simply hangs when node tries to restore the state for fd 0, stdin.

   I can't reproduce on Linux so this is with 99% certainty a bug in macOS's implementation of tcsetattr(). TBD if and how to work around that.

   edit: libc turns tcsetattr(TCSANOW) into ioctl(TIOCSETA) so this is most likely a kernel bug, not a libc bug.
4. bnoordhuis commented on Jul 4, 2019

   

   bnoordhuis

   on Jul 4, 2019

   Member

   More actions

   This minimal C test case shows the exact same behavior:

   #include <err.h>
   #include <termios.h>
   
   int
   main(void)
   {
           struct termios t;
           if (tcgetattr(0, &t))
                   err(1, "tcgetattr");
           if (tcsetattr(0, TCSANOW, &t))
                   err(1, "tcsetattr");
           return 0;
   }

   $ cc t.c
   
   $ ./a.out
   # ok
   
   $ cat <(./a.out)
   # hangs
   

   IOW, not a Node.js bug. I'll see if I can devise a workaround.
5. bnoordhuis commented on Jul 4, 2019

   

   bnoordhuis

   on Jul 4, 2019

   Member

   More actions

   Okay, I figured it out. The tcsetattr() call makes the kernel suspend node with a SIGTTOU signal.

   Apparently cat <(node -v) spawns node as a background job that doesn't own the TTY. On Linux that results in the tcsetattr() call failing with EIO (expected), on macOS it sends a SIGTTOU instead.

   A fix is on the way.

   👍React with 👍3Reacted by Gireesh Punathil, JounQin and The Zealot
6. sam-github commented on Jul 4, 2019

   

   sam-github

   on Jul 4, 2019

   Contributor

   More actions

   FWIW, I can repro on Linux, maybe because I'm using zsh not bash.
7. pull

   added a commit that references this issue on Jul 6, 2019

   src: block SIGTTOU before calling tcsetattr()

   ...

   b06ce0b
8. addaleax

   closed this as completedin b06ce0bon Jul 6, 2019
9. targos

   added a commit that references this issue on Jul 20, 2019

   src: block SIGTTOU before calling tcsetattr()

   ...

   d4113f9