From: "Jun T." <takimoto-j@kba.biglobe.ne.jp>
To: zsh-workers@zsh.org
Subject: accessing zpty after child has finished (Mac OS X)
Date: Tue, 17 Dec 2013 01:33:00 +0900 [thread overview]
Message-ID: <C87F9A07-1C5B-46BA-B2F7-DB07880651A7@kba.biglobe.ne.jp> (raw)
On Mac OS X, 'make check' succeeds normally, but zpty still has
some problems:
mac$ zpty x date
(date finishes immediately)
mac$ zpty -r x # (1): no output
mac$ zpty
(20359) x: date # should be (finished)
mac$ zpty -w x foo
(2): zsh goes into an infinite loop (100% cpu usage).
Suppose the child on the slave side of the pty has already finished,
and we try to read from the master by 'ret = read(master, buf, 1)'.
On Linux, what we get is either
the data written to the slave but not yet read from the master,
or ret = -1 (with errno set to EIO) if no such data remains.
On Mac OS X, the data not yet read by the master is lost,
and read() always returns 0 (not -1).
The infinite loop (2) is in ptywritestr(); the for loop starting at
line 676 of zpty.c never breaks and loops forever, because checkptycmd()
(called at line 689) doesn't set cmd->fin. The following patch solves
this problem, and I hope it does no harm on other OS.
I feel the data loss (1) is OK at least for now.
The only way I can think of to avoid the data loss is to open the
slave in the parent and keep the file descriptor open in the parent.
But I believe it causes trouble on other OS.
diff --git a/Src/Modules/zpty.c b/Src/Modules/zpty.c
index fca0cc1..b0c339b 100644
--- a/Src/Modules/zpty.c
+++ b/Src/Modules/zpty.c
@@ -510,7 +510,7 @@ checkptycmd(Ptycmd cmd)
if (cmd->read != -1 || cmd->fin)
return;
- if ((r = read(cmd->fd, &c, 1)) < 0) {
+ if ((r = read(cmd->fd, &c, 1)) <= 0) {
if (kill(cmd->pid, 0) < 0) {
cmd->fin = 1;
zclose(cmd->fd);
next reply other threads:[~2013-12-16 16:33 UTC|newest]
Thread overview: 2+ messages / expand[flat|nested] mbox.gz Atom feed top
2013-12-16 16:33 Jun T. [this message]
2013-12-16 18:15 ` Bart Schaefer
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