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_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.
46 lines
1.2 KiB
C
46 lines
1.2 KiB
C
#if !defined _ISOMAC && defined _IO_MTSAFE_IO
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# include <stdio-lock.h>
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#endif
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#include <libio/libio.h>
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#ifndef _ISOMAC
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#ifndef _LIBC_LIBIO_H
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#define _LIBC_LIBIO_H
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libc_hidden_proto (__overflow)
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libc_hidden_proto (__underflow)
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libc_hidden_proto (__uflow)
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libc_hidden_proto (__woverflow)
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libc_hidden_proto (__wunderflow)
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libc_hidden_proto (__wuflow)
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libc_hidden_proto (_IO_free_backup_area)
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libc_hidden_proto (_IO_free_wbackup_area)
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libc_hidden_proto (_IO_padn)
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libc_hidden_proto (_IO_putc)
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libc_hidden_proto (_IO_sgetn)
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libc_hidden_proto (_IO_vfprintf)
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libc_hidden_proto (_IO_vfscanf)
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#ifdef _IO_MTSAFE_IO
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# undef _IO_peekc
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# undef _IO_flockfile
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# undef _IO_funlockfile
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# undef _IO_ftrylockfile
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# define _IO_peekc(_fp) _IO_peekc_locked (_fp)
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# if _IO_lock_inexpensive
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# define _IO_flockfile(_fp) \
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if (((_fp)->_flags & _IO_USER_LOCK) == 0) _IO_lock_lock (*(_fp)->_lock)
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# define _IO_funlockfile(_fp) \
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if (((_fp)->_flags & _IO_USER_LOCK) == 0) _IO_lock_unlock (*(_fp)->_lock)
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# else
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# define _IO_flockfile(_fp) \
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if (((_fp)->_flags & _IO_USER_LOCK) == 0) _IO_flockfile (_fp)
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# define _IO_funlockfile(_fp) \
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if (((_fp)->_flags & _IO_USER_LOCK) == 0) _IO_funlockfile (_fp)
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# endif
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#endif /* _IO_MTSAFE_IO */
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#endif
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#endif
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