From 630e01a70312d8e6ad47aeba370228fc05c789a9 Mon Sep 17 00:00:00 2001 From: Lars Ingebrigtsen Date: Tue, 25 Jun 2019 00:46:02 +0200 Subject: [PATCH] Make message_to_stderr do one single fwrite * src/xdisp.c (message_to_stderr): When running as a batch process, the output from `message' goes to stderr, and has a newline appended. Rewrite the code so that only one fwrite is performed to enable messages that are shorter than PIPE_BUF (usually 4096 on modern operating systems) are written out as one chunk, as this will ensure that the messages are not interleaved with messages from other processes that are writing at the same time. This does not affect other stderr outputs, just the ones from `message'. --- src/xdisp.c | 16 ++++++++++++++-- 1 file changed, 14 insertions(+), 2 deletions(-) diff --git a/src/xdisp.c b/src/xdisp.c index 5d70440f1cb..25e8932945e 100644 --- a/src/xdisp.c +++ b/src/xdisp.c @@ -10705,10 +10705,22 @@ message_to_stderr (Lisp_Object m) else s = m; - fwrite (SDATA (s), SBYTES (s), 1, stderr); + /* We want to write this out with a single fwrite call so that + output doesn't interleave with other processes writing to + stderr at the same time. */ + { + int length = min (INT_MAX, SBYTES (s) + 1); + char *string = xmalloc (length); + + memcpy (string, SSDATA (s), length - 1); + string[length - 1] = '\n'; + fwrite (string, 1, length, stderr); + xfree (string); + } } - if (!cursor_in_echo_area) + else if (!cursor_in_echo_area) fputc ('\n', stderr); + fflush (stderr); } -- 2.30.2