Change internals of FILE: reuse the unget buffer field to access an

extended attribute data structure (pimpl idiom). Idea taken from citrus.
Much discussion with deraadt@, otto@, millert@...

This is the least disruptive way to extend FILE, since its size can't really
change without this being a flag day. So the size doesn't change.

Actual additions to the structure will come in separate steps, since this
change is nasty enough on its own.

Tests by otto@ and others, careful reading of code by otto@ and millert@.

This is definitely a major bump, and has been checked to not impact a
full ports build.

1 files changed, 42 insertions, 0 deletions

diff --git a/lib/libc/stdio/fileext.h b/lib/libc/stdio/fileext.h
new file mode 100644
index 00000000000..5619940c2bc
--- /dev/null
+++ b/lib/libc/stdio/fileext.h
@@ -0,0 +1,42 @@
+/*	$OpenBSD: fileext.h,v 1.1 2005/04/30 09:25:17 espie Exp $	*/
+/* $NetBSD: fileext.h,v 1.5 2003/07/18 21:46:41 nathanw Exp $ */
+
+/*-
+ * Copyright (c)2001 Citrus Project,
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ * 1. Redistributions of source code must retain the above copyright
+ *    notice, this list of conditions and the following disclaimer.
+ * 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.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
+ * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+ * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
+ * ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
+ * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
+ * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
+ * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
+ * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
+ * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
+ * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
+ * SUCH DAMAGE.
+ *
+ * $Citrus$
+ */
+
+/*
+ * file extension
+ */
+struct __sfileext {
+	struct	__sbuf _ub; /* ungetc buffer */
+	/* further data */
+};
+
+#define _EXT(fp) ((struct __sfileext *)((fp)->_ext._base))
+#define _UB(fp) _EXT(fp)->_ub
+#define _FILEEXT_SETUP(f, fext) /* LINTED */(f)->_ext._base = (unsigned char *)(fext)