Remove _IO_MTSAFE_IO from public headers.

_IO_MTSAFE_IO controls whether stdio is *built* with support for
multithreading.  In the distant past it might also have worked as a
feature selection macro, allowing library *users* to select
thread-safe or lock-free stdio at application build time, I haven't
done the archaeology.  Nowadays, defining _IO_MTSAFE_IO while using
the installed headers, or in _ISOMAC mode, will cause libio.h to throw
syntax errors.

This patch removes _IO_MTSAFE_IO from the public headers
(specifically, from libio/libio.h).  The most important thing it
controlled in there was whether libio.h defines _IO_lock_t itself or
expects stdio-lock.h to have done it, and we do still need a
inter-header communication macro for that, because stdio-lock.h can
only define _IO_lock_t as a typedef.  I've invented
_IO_lock_t_defined, which is defined by both versions of stdio-lock.h.

_IO_MTSAFE_IO also controlled the definitions of a handful of macros
that _might_ count as part of the public libio.h interface.  They are
now unconditionally given their non-_IO_MTSAFE_IO definition in
libio/libio.h, and include/libio.h redefines them with the
_IO_MTSAFE_IO definition.  This should minimize the odds of breaking
old software that actually uses those macros.

I suspect that this entire mechanism is vestigial, and that glibc
won't build anymore if you *don't* define _IO_MTSAFE_IO, but that's
another patchset.  The bulk of libio.h is internal-use-only stuff that
no longer makes sense to expose (libstdc++ gave up on making a FILE
the same object as a C++ filebuf *decades* ago) but that, too, is
another patchset.

	* libio/libio.h: Condition dummy definition of _IO_lock_t on
	_IO_lock_t_defined, not _IO_MTSAFE_IO. Unconditionally use the
	non-_IO_MTSAFE_IO definitions for _IO_peekc, _IO_flockfile,
	_IO_funlockfile, and _IO_ftrylockfile.  Only define
	_IO_cleanup_region_start and _IO_cleanup_region_end if not
	already defined.
	* include/libio.h: If _IO_MTSAFE_IO is defined, redefine
        _IO_peekc, _IO_flockfile, _IO_funlockfile, and _IO_ftrylockfile
        appropriately.
	* sysdeps/generic/stdio-lock.h, sysdeps/nptl/stdio-lock.h:
	Define _IO_lock_t_defined after defining _IO_lock_t.

1 files changed, 13 insertions, 18 deletions

diff --git a/libio/libio.h b/libio/libio.h
index 2241c1471d..518ffd8e44 100644
--- a/libio/libio.h
+++ b/libio/libio.h
@@ -143,10 +143,9 @@
 
 struct _IO_jump_t;  struct _IO_FILE;
 
-/* Handle lock.  */
-#ifdef _IO_MTSAFE_IO
-/* _IO_lock_t defined in internal headers during the glibc build.  */
-#else
+/* During the build of glibc itself, _IO_lock_t will already have been
+   defined by internal headers.  */
+#ifndef _IO_lock_t_defined
 typedef void _IO_lock_t;
 #endif
 
@@ -441,20 +440,16 @@ extern void _IO_flockfile (_IO_FILE *) __THROW;
 extern void _IO_funlockfile (_IO_FILE *) __THROW;
 extern int _IO_ftrylockfile (_IO_FILE *) __THROW;
 
-#ifdef _IO_MTSAFE_IO
-# define _IO_peekc(_fp) _IO_peekc_locked (_fp)
-# define _IO_flockfile(_fp) \
-  if (((_fp)->_flags & _IO_USER_LOCK) == 0) _IO_flockfile (_fp)
-# define _IO_funlockfile(_fp) \
-  if (((_fp)->_flags & _IO_USER_LOCK) == 0) _IO_funlockfile (_fp)
-#else
-# define _IO_peekc(_fp) _IO_peekc_unlocked (_fp)
-# define _IO_flockfile(_fp) /**/
-# define _IO_funlockfile(_fp) /**/
-# define _IO_ftrylockfile(_fp) /**/
-# define _IO_cleanup_region_start(_fct, _fp) /**/
-# define _IO_cleanup_region_end(_Doit) /**/
-#endif /* !_IO_MTSAFE_IO */
+#define _IO_peekc(_fp) _IO_peekc_unlocked (_fp)
+#define _IO_flockfile(_fp) /**/
+#define _IO_funlockfile(_fp) /**/
+#define _IO_ftrylockfile(_fp) /**/
+#ifndef _IO_cleanup_region_start
+#define _IO_cleanup_region_start(_fct, _fp) /**/
+#endif
+#ifndef _IO_cleanup_region_end
+#define _IO_cleanup_region_end(_Doit) /**/
+#endif
 
 extern int _IO_vfscanf (_IO_FILE * __restrict, const char * __restrict,
 			_IO_va_list, int *__restrict);