From: Joseph Myers <joseph@codesourcery.com>
To: Zack Weinberg <zackw@panix.com>
Cc: <libc-alpha@sourceware.org>, <adhemerval.zanella@linaro.org>,
<Wilco.Dijkstra@arm.com>, <fweimer@redhat.com>,
<carlos@redhat.com>, <schwab@suse.de>
Subject: Re: [PATCH 01/10] Remove _IO_MTSAFE_IO from public headers.
Date: Tue, 09 May 2017 21:11:00 -0000 [thread overview]
Message-ID: <alpine.DEB.2.20.1705092110550.28688@digraph.polyomino.org.uk> (raw)
In-Reply-To: <20170509154103.11973-2-zackw@panix.com>
On Tue, 9 May 2017, Zack Weinberg wrote:
> _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.
OK.
--
Joseph S. Myers
joseph@codesourcery.com
next prev parent reply other threads:[~2017-05-09 21:11 UTC|newest]
Thread overview: 51+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-05-09 15:41 [PATCH 00/10] All of my not-yet-reviewed patches Zack Weinberg
2017-05-09 15:41 ` [PATCH 09/10] Remove bits/string2.h Zack Weinberg
2017-05-09 15:41 ` [PATCH 01/10] Remove _IO_MTSAFE_IO from public headers Zack Weinberg
2017-05-09 21:11 ` Joseph Myers [this message]
2017-05-09 15:41 ` [PATCH 08/10] Don't install libio.h or _G_config.h Zack Weinberg
2017-05-09 15:41 ` [PATCH 04/10] Convert signal.h from __need macros to bits/types/ headers Zack Weinberg
2017-05-09 21:36 ` Joseph Myers
2017-05-17 17:41 ` Joseph Myers
2017-05-20 21:03 ` Zack Weinberg
2017-05-09 15:41 ` [PATCH 07/10] Remove __need_IOV_MAX and __need_FOPEN_MAX Zack Weinberg
2017-05-09 15:41 ` [PATCH 02/10] Suppress internal declarations for most of the testsuite Zack Weinberg
2017-05-09 21:28 ` Joseph Myers
2017-05-10 11:56 ` Zack Weinberg
2017-05-12 15:40 ` H.J. Lu
2017-05-12 16:16 ` Zack Weinberg
2017-05-12 16:26 ` H.J. Lu
2017-05-15 14:18 ` [PATCH] Move tst-mutex*8* to tests-internal Tulio Magno Quites Machado Filho
2017-05-20 13:06 ` Zack Weinberg
2017-05-22 14:21 ` Stefan Liebler
2017-05-25 17:55 ` Tulio Magno Quites Machado Filho
2017-05-09 15:41 ` [PATCH 03/10] The bits/types/*.h treatment for stdio and wchar Zack Weinberg
2017-05-09 21:34 ` Joseph Myers
2017-05-10 11:52 ` Zack Weinberg
2017-05-20 21:05 ` Zack Weinberg
2017-05-22 14:56 ` Joseph Myers
2017-05-09 15:56 ` [PATCH 10/10] Remove bits/string.h Zack Weinberg
2017-05-09 15:56 ` [PATCH 05/10] Remove __need macros from errno.h (__need_Emath, __need_error_t) Zack Weinberg
2017-05-09 21:38 ` Joseph Myers
2017-05-10 7:31 ` Florian Weimer
2017-05-10 11:49 ` Joseph Myers
2017-05-10 12:03 ` Florian Weimer
2017-05-11 12:15 ` Zack Weinberg
2017-05-11 14:30 ` Joseph Myers
2017-05-11 14:46 ` Zack Weinberg
2017-05-11 14:53 ` Florian Weimer
2017-05-11 14:48 ` Florian Weimer
2017-05-11 15:26 ` Joseph Myers
2017-05-11 15:42 ` Andreas Schwab
2017-05-11 16:10 ` Joseph Myers
2017-05-11 17:20 ` Andreas Schwab
2017-05-11 16:19 ` Florian Weimer
2017-05-11 17:25 ` Andreas Schwab
2017-05-12 6:23 ` Florian Weimer
2017-05-15 8:11 ` Andreas Schwab
2017-05-15 8:13 ` Florian Weimer
2017-05-15 8:24 ` Andreas Schwab
2017-05-15 9:08 ` Florian Weimer
2017-05-09 15:56 ` [PATCH 06/10] Remove __need_list_t and __need_res_state Zack Weinberg
2017-05-10 7:37 ` Florian Weimer
2017-05-20 19:37 ` Zack Weinberg
2017-05-11 0:12 ` [PATCH 00/10] All of my not-yet-reviewed patches Joseph Myers
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