master 7faea4a15e: When closing an Eshell process target, send EOF three times

[Lars Ingebrigtsen]

branch: master
commit 7faea4a15ead8307f59b055cfecba0928a9110c8
Author: Jim Porter <jporterbugs@gmail.com>
Commit: Lars Ingebrigtsen <larsi@gnus.org>

    When closing an Eshell process target, send EOF three times
    
    * lisp/eshell/esh-io.el (eshell-close-target): Send EOF 3 times.
    
    * test/lisp/eshell/em-extpipe-tests.el (em-extpipe-tests--deftest):
    Re-enable these tests on EMBA.
    
    This patch is adapted by one from Ken Brown, who uncovered the reason
    for this bug (bug#56025).
---
 lisp/eshell/esh-io.el                | 16 ++++++++++++++--
 test/lisp/eshell/em-extpipe-tests.el |  1 -
 2 files changed, 14 insertions(+), 3 deletions(-)

diff --git a/lisp/eshell/esh-io.el b/lisp/eshell/esh-io.el
index 3644c1a18b..c035890ddf 100644
--- a/lisp/eshell/esh-io.el
+++ b/lisp/eshell/esh-io.el
@@ -276,8 +276,20 @@ STATUS should be non-nil on successful termination of the 
output."
    ;; If we're redirecting to a process (via a pipe, or process
    ;; redirection), send it EOF so that it knows we're finished.
    ((eshell-processp target)
-    (if (eq (process-status target) 'run)
-       (process-send-eof target)))
+    ;; According to POSIX.1-2017, section 11.1.9, sending EOF causes
+    ;; all bytes waiting to be read to be sent to the process
+    ;; immediately.  Thus, if there are any bytes waiting, we need to
+    ;; send EOF twice: once to flush the buffer, and a second time to
+    ;; cause the next read() to return a size of 0, indicating
+    ;; end-of-file to the reading process.  However, some platforms
+    ;; (e.g. Solaris) actually require sending a *third* EOF.  Since
+    ;; sending extra EOFs while the process is running shouldn't break
+    ;; anything, we'll just send the maximum we'd ever need.  See
+    ;; bug#56025 for further details.
+    (let ((i 0))
+      (while (and (<= (cl-incf i) 3)
+                  (eq (process-status target) 'run))
+        (process-send-eof target))))
 
    ;; A plain function redirection needs no additional arguments
    ;; passed.
diff --git a/test/lisp/eshell/em-extpipe-tests.el 
b/test/lisp/eshell/em-extpipe-tests.el
index 3b84d763ac..29f5dc0551 100644
--- a/test/lisp/eshell/em-extpipe-tests.el
+++ b/test/lisp/eshell/em-extpipe-tests.el
@@ -71,7 +71,6 @@
        (skip-unless shell-file-name)
        (skip-unless shell-command-switch)
        (skip-unless (executable-find shell-file-name))
-       (skip-unless (not (getenv "EMACS_EMBA_CI")))
        (let ((input ,input))
          (with-temp-eshell ,@body)))))