From e02089e28a2f25aa7276e7e17af9746215c161ab Mon Sep 17 00:00:00 2001
From: obarthel <obarthel@gmx.net>
Date: Sat, 24 Aug 2019 14:05:09 +0200
Subject: [PATCH] Better handling of unbuffered mode for interactive streams

If the stream is unbuffered and turns out to be an interactive stream (e.g. stderr) then output will be made to follow the rules of line buffering to yield better readability of the output. Similar code exists with fputs(), for example.
---
 library/stdio_puts.c | 34 +++++++++++++++++++++++-----------
 1 file changed, 23 insertions(+), 11 deletions(-)

diff --git a/library/stdio_puts.c b/library/stdio_puts.c
index 92d5484..3883d8d 100644
--- a/library/stdio_puts.c
+++ b/library/stdio_puts.c
@@ -1,10 +1,8 @@
 /*
- * $Id: stdio_puts.c,v 1.8 2006-01-08 12:04:25 obarthel Exp $
- *
  * :ts=4
  *
  * Portable ISO 'C' (1994) runtime library for the Amiga computer
- * Copyright (c) 2002-2015 by Olaf Barthel <obarthel (at) gmx.net>
+ * Copyright (c) 2002-2019 by Olaf Barthel <obarthel (at) gmx.net>
  * All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
@@ -46,7 +44,8 @@
 int
 puts(const char *s)
 {
-	struct iob * file = (struct iob *)stdout;
+	FILE * stream = stdout;
+	struct iob * file = (struct iob *)stream;
 	int result = EOF;
 	int buffer_mode;
 	int c;
@@ -60,7 +59,7 @@ puts(const char *s)
 	if(__check_abort_enabled)
 		__check_abort();
 
-	flockfile(stdout);
+	flockfile(stream);
 
 	#if defined(CHECK_FOR_NULL_POINTERS)
 	{
@@ -76,20 +75,33 @@ puts(const char *s)
 	assert( FLAG_IS_SET(file->iob_Flags,IOBF_IN_USE) );
 	assert( file->iob_BufferSize > 0 );
 
+	/* If buffering is disabled for an interactive stream
+	   switch to line buffering to improve the readability of
+	   the output: instead of pumping out the entire buffer
+	   break it up into individual lines. */
 	buffer_mode = (file->iob_Flags & IOBF_BUFFER_MODE);
 	if(buffer_mode == IOBF_BUFFER_MODE_NONE)
-		buffer_mode = IOBF_BUFFER_MODE_LINE;
+	{
+		struct fd * fd = __fd[file->iob_Descriptor];
 
-	if(__fputc_check(stdout) < 0)
+		__fd_lock(fd);
+
+		if(FLAG_IS_SET(fd->fd_Flags,FDF_IS_INTERACTIVE))
+			buffer_mode = IOBF_BUFFER_MODE_LINE;
+
+		__fd_unlock(fd);
+	}
+
+	if(__fputc_check(stream) < 0)
 		goto out;
 
 	while((c = (*s++)) != '\0')
 	{
-		if(__putc(c,stdout,buffer_mode) == EOF)
+		if(__putc(c,stream,buffer_mode) == EOF)
 			goto out;
 	}
 
-	if(__putc('\n',stdout,buffer_mode) == EOF)
+	if(__putc('\n',stream,buffer_mode) == EOF)
 		goto out;
 
 	result = OK;
@@ -100,7 +112,7 @@ puts(const char *s)
 	   may have buffered data around, queued to be printed right now.
 	   This is intended to improve performance as it takes more effort
 	   to write a single character to a file than to write a bunch. */
-	if(result == 0 && (file->iob_Flags & IOBF_BUFFER_MODE) == IOBF_BUFFER_MODE_NONE)
+ if(result == 0 && (file->iob_Flags & IOBF_BUFFER_MODE) == IOBF_BUFFER_MODE_NONE)
 	{
 		if(__iob_write_buffer_is_valid(file) && __flush_iob_write_buffer(file) < 0)
 		{
@@ -109,7 +121,7 @@ puts(const char *s)
 		}
 	}
 
-	funlockfile(stdout);
+	funlockfile(stream);
 
 	RETURN(result);
 	return(result);