bug#66186: "make lisp/eshell/esh-proc-tests" fails intermittently since 7e50861ca7ed3f620fe62ac6572f6e88b3600ece

[Jim Porter <jporterbugs@gmail.com>]

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On 9/24/2023 9:52 PM, Eli Zaretskii wrote:
>> Date: Sun, 24 Sep 2023 16:02:03 -0700
>> From: Jim Porter <jporterbugs@gmail.com>
>>
>> However, I don't understand why this would cause an abort though;
>> normally, 'process-send-string' should just signal an Elisp error (which
>> Eshell then catches and does the right thing with it). Maybe there's a
>> bug somewhere in process.c where it's not correctly handling the (real)
>> SIGPIPE signal and converting it to an Elisp signal?
> 
> In batch mode, SIGPIPE is not ignored by Emacs, see init_signals.
> This was changed 11 years ago, see commit 4d7e6e51dd.

Thanks, I didn't realize that.

> Perhaps Eshell should check that the process is still alive before
> calling process-send-string?

Ok, how about this? Jens, could you try this patch out to see if it 
fixes things for you?

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From e9d961f0b1debed82fc004d6631ffe6adff7c19f Mon Sep 17 00:00:00 2001
From: Jim Porter <jporterbugs@gmail.com>
Date: Sun, 24 Sep 2023 22:30:34 -0700
Subject: [PATCH] Check for process liveness before calling
 'process-send-string' in Eshell

In other words, seek permission instead of asking for forgiveness
(bug#66186).

* lisp/eshell/esh-io.el (eshell-output-object-to-target): Check
'process-live-p' first.
---
 lisp/eshell/esh-io.el | 11 +++--------
 1 file changed, 3 insertions(+), 8 deletions(-)

diff --git a/lisp/eshell/esh-io.el b/lisp/eshell/esh-io.el
index cd0cee6e21d..668ff13b825 100644
--- a/lisp/eshell/esh-io.el
+++ b/lisp/eshell/esh-io.el
@@ -644,15 +644,10 @@ eshell-output-object-to-target
   "Output OBJECT to the process TARGET."
   (unless (stringp object)
     (setq object (eshell-stringify object)))
-  (condition-case err
+  (if (process-live-p target)
       (process-send-string target object)
-    (error
-     ;; If `process-send-string' raises an error and the process has
-     ;; finished, treat it as a broken pipe.  Otherwise, just
-     ;; re-throw the signal.
-     (if (process-live-p target)
-         (signal (car err) (cdr err))
-       (signal 'eshell-pipe-broken (list target)))))
+    ;; If the process is already dead, treat that as a broken pipe.
+    (signal 'eshell-pipe-broken (list target)))
   object)
 
 (cl-defmethod eshell-output-object-to-target (object
-- 
2.25.1