Use a better buffer size in emacs_perror

* src/sysdep.c (emacs_perror): Since the buffer is for avoiding
interleaving, size it via PIPE_BUF not BUFSIZ.
* src/sysstdio.h (PIPE_BUF): Provide a default.

2 files changed, 7 insertions, 2 deletions

diff --git a/src/sysdep.c b/src/sysdep.c
index 4c3d546962c..9301405943b 100644
--- a/src/sysdep.c
+++ b/src/sysdep.c
@@ -2711,10 +2711,10 @@ emacs_perror (char const *message)
                          ? initial_argv[0] : "emacs");
   /* Write it out all at once, if it's short; this is less likely to
      be interleaved with other output.  */
-  char buf[BUFSIZ];
+  char buf[min (PIPE_BUF, MAX_ALLOCA)];
   int nbytes = snprintf (buf, sizeof buf, "%s: %s: %s\n",
                          command, message, error_string);
-  if (0 <= nbytes && nbytes < BUFSIZ)
+  if (0 <= nbytes && nbytes < sizeof buf)
     emacs_write (STDERR_FILENO, buf, nbytes);
   else
     {
diff --git a/src/sysstdio.h b/src/sysstdio.h
index 5303e8a15b2..637f5fdfa6d 100644
--- a/src/sysstdio.h
+++ b/src/sysstdio.h
@@ -21,6 +21,7 @@ along with GNU Emacs.  If not, see <https://www.gnu.org/licenses/>.  */
 #define EMACS_SYSSTDIO_H
 
 #include <fcntl.h>
+#include <limits.h>
 #include <stdio.h>
 #include "unlocked-io.h"
 
@@ -38,4 +39,8 @@ extern void close_output_streams (void);
 # define FOPEN_TEXT ""
 #endif
 
+#ifndef PIPE_BUF
+ #define PIPE_BUF MAX_ALLOCA
+#endif
+
 #endif /* EMACS_SYSSTDIO_H */