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bug#63078: 26.1; Sentinels are sometimes unexpectedly only invoked in sc
From: |
Eli Zaretskii |
Subject: |
bug#63078: 26.1; Sentinels are sometimes unexpectedly only invoked in script mode |
Date: |
Wed, 26 Apr 2023 09:22:02 +0300 |
> From: Markus Triska <triska@metalevel.at>
> Date: Wed, 26 Apr 2023 01:15:36 +0200
>
> to reproduce this issue, please save the following C code in proc.c:
>
> #include <stdio.h>
> #include <stdlib.h>
> int main() {
> printf("hello");
> exit(0);
> }
>
> and compile it, yielding the program file "./proc":
>
> $ gcc proc.c -o proc
>
> Further, please store the following Elisp definitions in proc.el, in
> the same directory as the above program:
>
> (add-to-list 'exec-path ".")
>
> (defvar p-stopped nil)
>
> (defun my-sentinel (proc str)
> (when (string-match "^\\(?:finished\n\\|exited abnormally\\|killed\n\\)"
> str)
> (setq p-stopped t)))
>
> (defun wait-for-process-end (proc)
> (while (not p-stopped)
> (message "process status is: %s" (process-status proc))
> (accept-process-output proc 0.1 nil t)))
>
> (defun f ()
> (with-temp-buffer
> (let ((proc (start-process "p" (current-buffer) "proc")))
> (setq p-stopped nil)
> (set-process-sentinel proc 'my-sentinel)
> (wait-for-process-end proc))
> (message "process said: %s" (buffer-string))))
>
> The following invocation and result shows a case where the program
> behaves exactly as intended: It waits for the process sentinel to
> signal that no more output can arrive from the process, and shows the
> output it got while the process was producing output:
>
> $ emacs -Q --script proc.el --eval "(f)"
> process status is: exit
> process said: hello
>
> In contrast, the following invocation produces, in the echo area, the
> message "process status is: exit", and Emacs hangs unexpectedly:
>
> $ emacs -Q -l proc.el --eval "(f)"
>
> The behaviour I expect in this case is analogous to the other
> invocation: I do expect the message we see, followed by the message
> "process said: hello", as in the case above. However, this second
> message only appears if I manually interrupt Emacs with C-g.
I cannot reproduce the problem with Emacs 28.2: I get "process said:
hello" in the echo-area, as expected. Did you try with the -nw
command-line switch, and if you do, does it change anything?
It could be some timing problem: you start a program that exits almost
immediately, so there could be some race condition between the program
and your code.