--- Libc/Libc-583/stdio/FreeBSD/makebuf.c
+++ Libc/Libc-1534.40.2/stdio/FreeBSD/makebuf.c
@@ -1,4 +1,6 @@
 /*-
+ * SPDX-License-Identifier: BSD-3-Clause
+ *
  * Copyright (c) 1990, 1993
  *	The Regents of the University of California.  All rights reserved.
  *
@@ -13,11 +15,7 @@
  * 2. Redistributions in binary form must reproduce the above copyright
  *    notice, this list of conditions and the following disclaimer in the
  *    documentation and/or other materials provided with the distribution.
- * 3. All advertising materials mentioning features or use of this software
- *    must display the following acknowledgement:
- *	This product includes software developed by the University of
- *	California, Berkeley and its contributors.
- * 4. Neither the name of the University nor the names of its contributors
+ * 3. Neither the name of the University nor the names of its contributors
  *    may be used to endorse or promote products derived from this software
  *    without specific prior written permission.
  *
@@ -38,7 +36,7 @@
 static char sccsid[] = "@(#)makebuf.c	8.1 (Berkeley) 6/4/93";
 #endif /* LIBC_SCCS and not lint */
 #include <sys/cdefs.h>
-__FBSDID("$FreeBSD: src/lib/libc/stdio/makebuf.c,v 1.4 2002/03/22 21:53:04 obrien Exp $");
+__FBSDID("$FreeBSD$");
 
 #include "namespace.h"
 #include <sys/types.h>
@@ -46,8 +44,119 @@
 #include <unistd.h>
 #include <stdio.h>
 #include <stdlib.h>
+#include "un-namespace.h"
+
+#include "libc_private.h"
 #include "local.h"
-#include "un-namespace.h"
+#include <xlocale/_stdio.h>
+#include <xlocale/_stdlib.h>
+#include <os/once_private.h>
+
+#ifdef FEATURE_SMALL_STDIOBUF
+# define MAXBUFSIZE	(1 << 12)
+#else
+# define MAXBUFSIZE	(1 << 16)
+#endif
+
+#define TTYBUFSIZE	4096
+#define MAXEVPSIZE 16
+
+static char __fallback_evp[MAXEVPSIZE];
+static char __stdout_evp[MAXEVPSIZE];
+
+static void
+__loadevp(const char* key, char destination[MAXEVPSIZE])
+{
+	char* evp = getenv(key);
+	if (evp != NULL) {
+		strlcpy(destination, evp, MAXEVPSIZE);
+	} else {
+		destination[0] = '\0';
+	}
+}
+
+static void
+__evpinit(void* __unused unused)
+{
+	__loadevp("STDBUF", __fallback_evp);
+	__loadevp("STDBUF1", __stdout_evp);
+}
+
+static char*
+__getevp(int fd)
+{
+	static os_once_t predicate;
+	os_once(&predicate, NULL, __evpinit);
+
+	if (fd == STDOUT_FILENO && __stdout_evp[0] != '\0') {
+		return __stdout_evp;
+	} else if (__fallback_evp[0] != '\0') {
+		return __fallback_evp;
+	} else {
+		return NULL;
+	}
+
+}
+
+/*
+ * Internal routine to determine environment override buffering for a file.
+ *
+ * Sections of the below taken from NetBSD's version of this file under the same license.
+ */
+static int
+__senvbuf(FILE *fp, size_t *bufsize, int *couldbetty)
+{
+	char* evp;
+	char* end;
+	int flags;
+	long size;
+
+	flags = 0; // Default to fully buffered
+
+	if ((evp = __getevp(fp->_file)) == NULL) {
+		return flags;
+	}
+
+	// Look at the first character only to determine buffering mode
+	switch (*evp) {
+		case 'u':
+		case 'U':
+			flags |= __SNBF;
+			break;
+		case 'l':
+		case 'L':
+			flags |= __SLBF;
+			break;
+		case 'f':
+		case 'F':
+			// Default flags is fully buffered
+			break;
+		default:
+			// Unexpected buffering mode, use default fully buffered
+			return flags;
+	}
+	// User specified envrionment defaults have higher priority than tty defaults
+	*couldbetty = 0;
+
+	// Advance the envrionment variable pointer, so we can attempt to parse the number
+	evp++;
+	if (!isdigit(*evp)) {
+		return flags; // No number found, this protects us from negative size values
+	}
+
+	size = strtol_l(evp, &end, 10, LC_C_LOCALE);
+	if (*end != '\0') {
+		return flags;
+	}
+
+	if (size <= 0) {
+		return __SNBF; // Override with unbuffered if the buffer size is 0
+	}
+
+	// We had a non zero buffer, cap it and return the flags;
+	*bufsize = size > MAXBUFSIZE ? MAXBUFSIZE : size;
+	return flags;
+}
 
 /*
  * Allocate a file buffer, or switch to unbuffered I/O.
@@ -57,8 +166,7 @@
  * optimisation) right after the _fstat() that finds the buffer size.
  */
 void
-__smakebuf(fp)
-	FILE *fp;
+__smakebuf(FILE *fp)
 {
 	void *p;
 	int flags;
@@ -71,6 +179,23 @@
 		return;
 	}
 	flags = __swhatbuf(fp, &size, &couldbetty);
+	if (fp->_file >= 0) {
+		flags |= __senvbuf(fp, &size, &couldbetty);
+
+		if (flags & __SNBF) {
+			fp->_flags |= __SNBF;
+			fp->_bf._base = fp->_p = fp->_nbuf;
+			fp->_bf._size = 1;
+			return;
+		}
+	}
+
+	if (couldbetty && isatty(fp->_file)) {
+		flags |= __SLBF;
+		/* st_blksize for ttys is 128K, so make it more reasonable */
+		if (size > TTYBUFSIZE)
+			fp->_blksize = size = TTYBUFSIZE;
+	}
 	if ((p = malloc(size)) == NULL) {
 		fp->_flags |= __SNBF;
 		fp->_bf._base = fp->_p = fp->_nbuf;
@@ -81,8 +206,6 @@
 	flags |= __SMBF;
 	fp->_bf._base = fp->_p = p;
 	fp->_bf._size = size;
-	if (couldbetty && isatty(fp->_file))
-		flags |= __SLBF;
 	fp->_flags |= flags;
 }
 
@@ -90,10 +213,7 @@
  * Internal routine to determine `proper' buffering for a file.
  */
 int
-__swhatbuf(fp, bufsize, couldbetty)
-	FILE *fp;
-	size_t *bufsize;
-	int *couldbetty;
+__swhatbuf(FILE *fp, size_t *bufsize, int *couldbetty)
 {
 	struct stat st;
 
@@ -115,8 +235,7 @@
 	 * __sseek is mainly paranoia.)  It is safe to set _blksize
 	 * unconditionally; it will only be used if __SOPT is also set.
 	 */
-	*bufsize = st.st_blksize;
-	fp->_blksize = st.st_blksize;
+	fp->_blksize = *bufsize = st.st_blksize > MAXBUFSIZE ? MAXBUFSIZE : st.st_blksize;
 	return ((st.st_mode & S_IFMT) == S_IFREG && fp->_seek == __sseek ?
 	    __SOPT : __SNPT);
 }