From: Paul Eggert <eggert@cs.ucla.edu>
Date: Thu, 11 Mar 2021 18:35:04 +0000 (-0800)
Subject: On MS-Windows, fflush stderr after newline
X-Git-Tag: emacs-28.0.90~3317
X-Git-Url: http://git.eshelyaron.com/gitweb/?a=commitdiff_plain;h=b8bf62b60a63e4af4be0cfdd7b4e0d4b424af45c;p=emacs.git

On MS-Windows, fflush stderr after newline

Problem reported by Ioannis Kappas (Bug#46388).
* src/sysdep.c (errputc) [WINDOWSNT]: Flush stderr after newline.
---

diff --git a/src/sysdep.c b/src/sysdep.c
index 24d8832b2f3..d940acc4e05 100644
--- a/src/sysdep.c
+++ b/src/sysdep.c
@@ -2670,6 +2670,13 @@ void
 errputc (int c)
 {
   fputc_unlocked (c, errstream ());
+
+#ifdef WINDOWSNT
+  /* Flush stderr after outputting a newline since stderr is fully
+     buffered when redirected to a pipe, contrary to POSIX.  */
+  if (c == '\n')
+    fflush_unlocked (stderr);
+#endif
 }
 
 void