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author | Eli Zaretskii <eliz@gnu.org> | 2019-04-20 10:21:02 +0300 |
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committer | Eli Zaretskii <eliz@gnu.org> | 2019-04-20 10:21:02 +0300 |
commit | f90a3360d8c724d61ff89a2e788542a4ff6cb352 (patch) | |
tree | 434345009b0eef9981ca91c9abd5e416b98946d8 | |
parent | 037970f1af6c87767501ac6d46c50abe9d3f44e0 (diff) | |
download | emacs-f90a3360d8c724d61ff89a2e788542a4ff6cb352.tar.gz |
Backport doc improvement in ELisp manual
* doc/lispref/processes.texi (Accepting Output): Backport:
document how do avoid race conditions while waiting for all of
the process's output to arrive.
-rw-r--r-- | doc/lispref/processes.texi | 20 |
1 files changed, 20 insertions, 0 deletions
diff --git a/doc/lispref/processes.texi b/doc/lispref/processes.texi index d2ab518e5eb..7331eb63762 100644 --- a/doc/lispref/processes.texi +++ b/doc/lispref/processes.texi @@ -1834,6 +1834,26 @@ corresponding connection contains buffered data. The function returns arrived. @end defun +If a connection from a process contains buffered data, +@code{accept-process-output} can return non-@code{nil} even after the +process has exited. Therefore, although the following loop: + +@example +;; This loop contains a bug. +(while (process-live-p process) + (accept-process-output process)) +@end example + +@noindent +will often read all output from @var{process}, it has a race condition +and can miss some output if @code{process-live-p} returns @code{nil} +while the connection still contains data. Better is to write the loop +like this: + +@example +(while (accept-process-output process)) +@end example + @node Processes and Threads @subsection Processes and Threads @cindex processes, threads |