From 976d68677934ece87fc37cd0761512f5d43e0fe6 Mon Sep 17 00:00:00 2001
From: Jonas 'Sortie' Termansen <sortie@maxsi.org>
Date: Sun, 1 Mar 2020 16:00:52 +0100
Subject: [PATCH] Fix fputc(3) potentially miswriting the next byte after
 flushing.

---
 libc/stdio/fputc_unlocked.c | 9 ++-------
 1 file changed, 2 insertions(+), 7 deletions(-)

diff --git a/libc/stdio/fputc_unlocked.c b/libc/stdio/fputc_unlocked.c
index 9868cd26..8ac137c6 100644
--- a/libc/stdio/fputc_unlocked.c
+++ b/libc/stdio/fputc_unlocked.c
@@ -45,15 +45,10 @@ int fputc_unlocked(int c, FILE* fp)
 	fp->flags |= _FILE_LAST_WRITE;
 	fp->flags &= ~_FILE_STATUS_EOF;
 
-	if ( fp->amount_output_buffered == BUFSIZ )
-	{
-		if ( fflush_unlocked(fp) == EOF )
-			return EOF;
-	}
-
 	fp->buffer[fp->amount_output_buffered++] = c;
 
-	if ( fp->buffer_mode == _IOLBF && c == '\n' )
+	if ( fp->amount_output_buffered == BUFSIZ ||
+	     (fp->buffer_mode == _IOLBF && c == '\n') )
 	{
 		if ( fflush_unlocked(fp) == EOF )
 			return EOF;