[PATCH 6/6] Remove completely unused libio flag bits.

[Zack Weinberg <zackw at panix dot com>]

These macros are used literally nowhere in the source tree, and all
of them appear to relate to the C++ functionality of the original
libio that never got taken into glibc in the first place.  I also
reformatted the first set of flags to make it really obvious which
bits are not used (there's one bit that never gets set by current
code but might get set by old code).

This is as far as I propose to go in this patchset.  The next most
pressing changes are to eliminate _IO_MTSAFE_IO and to start removing
support for deprecated-but-exported _IO_ symbols, and both of those I
believe Florian has already been working on, so I'll leave them to
him.

	* libio/libio.h (_IOS_ATEND, _IOS_APPEND, _IOS_TRUNC)
	(_IOS_NOCREATE, _IOS_NOREPLACE, _IOS_BIN, _OLD_STDIO_MAGIC)
	(_IO_SKIPWS, _IO_LEFT, _IO_RIGHT, _IO_INTERNAL, _IO_DEC)
	(_IO_OCT, _IO_HEX, _IO_SHOWBASE, _IO_SHOWPOINT, _IO_UPPERCASE)
	(_IO_SHOWPOS, _IO_SCIENTIFIC, _IO_FIXED, _IO_UNITBUF, _IO_STDIO)
	(_IO_DONT_CLOSE, _IO_BOOLALPHA): Remove, unused.
	(_IO_BAD_SEEN): Comment out but leave as documentation.
	Reformat bit flags for _flags field to make occupancy clearer.
	Update commentary.
	* libio/bits/types/struct_FILE.h (_IO_EOF_SEEN, _IO_ERR_SEEN):
	Keep definitions consistent with those in libio/libio.h.
---
 libio/bits/types/struct_FILE.h |  4 +--
 libio/libio.h                  | 77 ++++++++++++++----------------------------
 2 files changed, 27 insertions(+), 54 deletions(-)

diff --git a/libio/bits/types/struct_FILE.h b/libio/bits/types/struct_FILE.h
index a120c762685..359f9494534 100644
--- a/libio/bits/types/struct_FILE.h
+++ b/libio/bits/types/struct_FILE.h
@@ -108,10 +108,10 @@ struct _IO_FILE_complete
    ? __overflow (_fp, (unsigned char) (_ch))				\
    : (unsigned char) (*(_fp)->_IO_write_ptr++ = (_ch)))
 
-#define _IO_EOF_SEEN 0x10
+#define _IO_EOF_SEEN 0x0010
 #define __feof_unlocked_body(_fp) (((_fp)->_flags & _IO_EOF_SEEN) != 0)
 
-#define _IO_ERR_SEEN 0x20
+#define _IO_ERR_SEEN 0x0020
 #define __ferror_unlocked_body(_fp) (((_fp)->_flags & _IO_ERR_SEEN) != 0)
 
 #define _IO_USER_LOCK 0x8000
diff --git a/libio/libio.h b/libio/libio.h
index 1371161e025..b25e583a794 100644
--- a/libio/libio.h
+++ b/libio/libio.h
@@ -60,42 +60,34 @@ typedef union
 
 #include <shlib-compat.h>
 
-/* open modes */
+/* _IO_seekoff modes */
 #define _IOS_INPUT	1
 #define _IOS_OUTPUT	2
-#define _IOS_ATEND	4
-#define _IOS_APPEND	8
-#define _IOS_TRUNC	16
-#define _IOS_NOCREATE	32
-#define _IOS_NOREPLACE	64
-#define _IOS_BIN	128
-
-/* Magic numbers and bits for the _flags field.
-   The magic numbers use the high-order bits of _flags;
-   the remaining bits are available for variable flags.
-   Note: The magic numbers must all be negative if stdio
-   emulation is desired. */
-
-#define _IO_MAGIC 0xFBAD0000 /* Magic number */
-#define _OLD_STDIO_MAGIC 0xFABC0000 /* Emulate old stdio. */
-#define _IO_MAGIC_MASK 0xFFFF0000
-#define _IO_USER_BUF 1 /* User owns buffer; don't delete it on close. */
-#define _IO_UNBUFFERED 2
-#define _IO_NO_READS 4 /* Reading not allowed */
-#define _IO_NO_WRITES 8 /* Writing not allowd */
-#define _IO_EOF_SEEN 0x10
-#define _IO_ERR_SEEN 0x20
-#define _IO_DELETE_DONT_CLOSE 0x40 /* Don't call close(_fileno) on cleanup. */
-#define _IO_LINKED 0x80 /* Set if linked (using _chain) to streambuf::_list_all.*/
-#define _IO_IN_BACKUP 0x100
-#define _IO_LINE_BUF 0x200
-#define _IO_TIED_PUT_GET 0x400 /* Set if put and get pointer logicly tied. */
-#define _IO_CURRENTLY_PUTTING 0x800
-#define _IO_IS_APPENDING 0x1000
-#define _IO_IS_FILEBUF 0x2000
-#define _IO_BAD_SEEN 0x4000
-#define _IO_USER_LOCK 0x8000
 
+/* Magic number and bits for the _flags field.  The magic number is
+   mostly vestigial, but preserved for compatibility.  It occupies the
+   high 16 bits of _flags; the low 16 bits are actual flag bits.  */
+
+#define _IO_MAGIC         0xFBAD0000 /* Magic number */
+#define _IO_MAGIC_MASK    0xFFFF0000
+#define _IO_USER_BUF          0x0001 /* Don't deallocate buffer on close. */
+#define _IO_UNBUFFERED        0x0002
+#define _IO_NO_READS          0x0004 /* Reading not allowed.  */
+#define _IO_NO_WRITES         0x0008 /* Writing not allowed.  */
+#define _IO_EOF_SEEN          0x0010
+#define _IO_ERR_SEEN          0x0020
+#define _IO_DELETE_DONT_CLOSE 0x0040 /* Don't call close(_fileno) on close.  */
+#define _IO_LINKED            0x0080 /* In the list of all open files.  */
+#define _IO_IN_BACKUP         0x0100
+#define _IO_LINE_BUF          0x0200
+#define _IO_TIED_PUT_GET      0x0400 /* Put and get pointer move in unison.  */
+#define _IO_CURRENTLY_PUTTING 0x0800
+#define _IO_IS_APPENDING      0x1000
+#define _IO_IS_FILEBUF        0x2000
+/*#define _IO_BAD_SEEN        0x4000  No longer used, reserved for compat.  */
+#define _IO_USER_LOCK         0x8000
+
+/* Bits for the _flags2 field.  */
 #define _IO_FLAGS2_MMAP 1
 #define _IO_FLAGS2_NOTCANCEL 2
 #define _IO_FLAGS2_FORTIFY 4
@@ -105,25 +97,6 @@ typedef union
 #define _IO_FLAGS2_CLOEXEC 64
 #define _IO_FLAGS2_NEED_LOCK 128
 
-/* These are "formatting flags" matching the iostream fmtflags enum values. */
-#define _IO_SKIPWS 01
-#define _IO_LEFT 02
-#define _IO_RIGHT 04
-#define _IO_INTERNAL 010
-#define _IO_DEC 020
-#define _IO_OCT 040
-#define _IO_HEX 0100
-#define _IO_SHOWBASE 0200
-#define _IO_SHOWPOINT 0400
-#define _IO_UPPERCASE 01000
-#define _IO_SHOWPOS 02000
-#define _IO_SCIENTIFIC 04000
-#define _IO_FIXED 010000
-#define _IO_UNITBUF 020000
-#define _IO_STDIO 040000
-#define _IO_DONT_CLOSE 0100000
-#define _IO_BOOLALPHA 0200000
-
 /* _IO_pos_BAD is an off64_t value indicating error, unknown, or EOF. */
 #define _IO_pos_BAD ((off64_t) -1)
 
-- 
2.16.1