Re: single-threaded optimizations

[Bruno Haible]

> > * We establish a new macro GNULIB_MBTOWC_SINGLE which means "assume that 
> > at most one thread invokes mbtowc-like functions". The mbtowc 
> > replacement uses this instead of using USE_UNLOCKED_IO. Tar can #define 
> > this new macro.
> 
> I like this idea. The packages can then define or not define each such
> macro individually.

Implemented through the following series of patches.


2021-03-07  Bruno Haible  <bruno@clisp.org>

        Rename GNULIB_WCHAR_SINGLE to GNULIB_WCHAR_SINGLE_LOCALE.
        * lib/lc-charset-dispatch.c: Test GNULIB_WCHAR_SINGLE_LOCALE instead of
        GNULIB_WCHAR_SINGLE.
        * lib/wcwidth.c: Likewise.
        * tests/test-wcwidth.c: Likewise.
        * doc/multithread.texi: Document GNULIB_WCHAR_SINGLE_LOCALE instead of
        GNULIB_WCHAR_SINGLE.
        * NEWS: Document the change.

2021-03-06  Bruno Haible  <bruno@clisp.org>

        mbrtowc: Allow locking optimization independently of 'unlocked-io'.
        * lib/mbtowc-lock.h: Test GNULIB_MBRTOWC_SINGLE_THREAD instead of
        USE_UNLOCKED_IO.
        * doc/multithread.texi: Document GNULIB_MBRTOWC_SINGLE_THREAD.

2021-03-06  Bruno Haible  <bruno@clisp.org>

        regex: Allow locking optimization independently of 'unlocked-io'.
        * lib/regex_internal.h: Test GNULIB_REGEX_SINGLE_THREAD instead of
        USE_UNLOCKED_IO.
        * doc/multithread.texi: Document GNULIB_REGEX_SINGLE_THREAD.

2021-03-06  Bruno Haible  <bruno@clisp.org>

        exclude: Allow stdio optimization independently of 'unlocked-io'.
        * lib/exclude.c: Test GNULIB_EXCLUDE_SINGLE_THREAD instead of
        USE_UNLOCKED_IO.
        * modules/exclude (Depends-on): Add unlocked-io-internal.
        * doc/multithread.texi: Document GNULIB_EXCLUDE_SINGLE_THREAD.

2021-03-06  Bruno Haible  <bruno@clisp.org>

        readutmp: Optimize stdio accesses.
        * lib/readutmp.c: Include unlocked-io.h unconditionally.
        * modules/readutmp (Depends-on): Add unlocked-io-internal.

2021-03-06  Bruno Haible  <bruno@clisp.org>

        mountlist: Optimize stdio accesses.
        * lib/mountlist.c: Include unlocked-io.h unconditionally.
        * modules/mountlist (Depends-on): Add unlocked-io-internal.

2021-03-06  Bruno Haible  <bruno@clisp.org>

        getusershell: Optimize stdio accesses when possible.
        * lib/getusershell.c: Test GNULIB_GETUSERSHELL_SINGLE_THREAD instead of
        USE_UNLOCKED_IO.
        * modules/getusershell (Depends-on): Add unlocked-io-internal.
        * doc/multithread.texi: Document GNULIB_GETUSERSHELL_SINGLE_THREAD.

2021-03-06  Bruno Haible  <bruno@clisp.org>

        unlocked-io-internal: New module.
        * m4/unlocked-io.m4 (gl_FUNC_GLIBC_UNLOCKED_IO): Don't define
        USE_UNLOCKED_IO here.
        * modules/unlocked-io-internal: New file, based on modules/unlocked-io.
        * modules/unlocked-io (Description): Clarify.
        (Files, Depends-on): Just use the unlocked-io-internal module.
        (configure.ac): Define GNULIB_STDIO_SINGLE_THREAD and USE_UNLOCKED_IO
        here.
        * doc/multithread.texi: Clarify when the 'unlocked-io' module can be
        used.

2021-03-06  Bruno Haible  <bruno@clisp.org>

        posixtm: Remove unused includes.
        * lib/posixtm.c: Don't include <stdio.h>, <sys/types.h>, unlocked-io.h.

0001-posixtm-Remove-unused-includes.patch
Description: Text Data

0002-unlocked-io-internal-New-module.patch
Description: Text Data

0003-getusershell-Optimize-stdio-accesses-when-possible.patch
Description: Text Data

0004-mountlist-Optimize-stdio-accesses.patch
Description: Text Data

0005-readutmp-Optimize-stdio-accesses.patch
Description: Text Data

0006-exclude-Allow-stdio-optimization-independently-of-un.patch
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0007-regex-Allow-locking-optimization-independently-of-un.patch
Description: Text Data

0008-mbrtowc-Allow-locking-optimization-independently-of-.patch
Description: Text Data

0009-Rename-GNULIB_WCHAR_SINGLE-to-GNULIB_WCHAR_SINGLE_LO.patch
Description: Text Data