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1711991592
_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.
112 lines
3.5 KiB
C
112 lines
3.5 KiB
C
/* Thread package specific definitions of stream lock type. NPTL version.
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Copyright (C) 2000-2017 Free Software Foundation, Inc.
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This file is part of the GNU C Library.
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The GNU C Library is free software; you can redistribute it and/or
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modify it under the terms of the GNU Lesser General Public
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License as published by the Free Software Foundation; either
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version 2.1 of the License, or (at your option) any later version.
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The GNU C Library is distributed in the hope that it will be useful,
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but WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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Lesser General Public License for more details.
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You should have received a copy of the GNU Lesser General Public
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License along with the GNU C Library; if not, see
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<http://www.gnu.org/licenses/>. */
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#ifndef _STDIO_LOCK_H
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#define _STDIO_LOCK_H 1
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#include <libc-lock.h>
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#include <lowlevellock.h>
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/* The locking here is very inexpensive, even for inlining. */
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#define _IO_lock_inexpensive 1
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typedef struct { int lock; int cnt; void *owner; } _IO_lock_t;
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#define _IO_lock_t_defined 1
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#define _IO_lock_initializer { LLL_LOCK_INITIALIZER, 0, NULL }
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#define _IO_lock_init(_name) \
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((void) ((_name) = (_IO_lock_t) _IO_lock_initializer))
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#define _IO_lock_fini(_name) \
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((void) 0)
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#define _IO_lock_lock(_name) \
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do { \
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void *__self = THREAD_SELF; \
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if ((_name).owner != __self) \
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{ \
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lll_lock ((_name).lock, LLL_PRIVATE); \
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(_name).owner = __self; \
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} \
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++(_name).cnt; \
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} while (0)
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#define _IO_lock_trylock(_name) \
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({ \
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int __result = 0; \
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void *__self = THREAD_SELF; \
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if ((_name).owner != __self) \
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{ \
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if (lll_trylock ((_name).lock) == 0) \
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{ \
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(_name).owner = __self; \
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(_name).cnt = 1; \
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} \
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else \
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__result = EBUSY; \
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} \
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else \
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++(_name).cnt; \
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__result; \
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})
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#define _IO_lock_unlock(_name) \
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do { \
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if (--(_name).cnt == 0) \
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{ \
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(_name).owner = NULL; \
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lll_unlock ((_name).lock, LLL_PRIVATE); \
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} \
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} while (0)
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#define _IO_cleanup_region_start(_fct, _fp) \
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__libc_cleanup_region_start (((_fp)->_flags & _IO_USER_LOCK) == 0, _fct, _fp)
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#define _IO_cleanup_region_start_noarg(_fct) \
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__libc_cleanup_region_start (1, _fct, NULL)
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#define _IO_cleanup_region_end(_doit) \
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__libc_cleanup_region_end (_doit)
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#if defined _LIBC && IS_IN (libc)
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# ifdef __EXCEPTIONS
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# define _IO_acquire_lock(_fp) \
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do { \
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_IO_FILE *_IO_acquire_lock_file \
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__attribute__((cleanup (_IO_acquire_lock_fct))) \
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= (_fp); \
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_IO_flockfile (_IO_acquire_lock_file);
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# define _IO_acquire_lock_clear_flags2(_fp) \
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do { \
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_IO_FILE *_IO_acquire_lock_file \
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__attribute__((cleanup (_IO_acquire_lock_clear_flags2_fct))) \
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= (_fp); \
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_IO_flockfile (_IO_acquire_lock_file);
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# else
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# define _IO_acquire_lock(_fp) _IO_acquire_lock_needs_exceptions_enabled
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# define _IO_acquire_lock_clear_flags2(_fp) _IO_acquire_lock (_fp)
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# endif
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# define _IO_release_lock(_fp) ; } while (0)
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#endif
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#endif /* stdio-lock.h */
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