From: Aurelien Jarno <aurelien@aurel32.net>
To: Adhemerval Zanella Netto <adhemerval.zanella@linaro.org>
Cc: Florian Weimer <fweimer@redhat.com>, libc-alpha@sourceware.org
Subject: Re: [PATCH] io: Fix record locking contants for powerpc64 with __USE_FILE_OFFSET64
Date: Tue, 29 Aug 2023 18:30:17 +0200 [thread overview]
Message-ID: <ZO4dGXTOMgEUq0nE@aurel32.net> (raw)
In-Reply-To: <a2369767-f606-d7a1-11e1-065a0a4c0dfa@linaro.org>
On 2023-08-29 10:20, Adhemerval Zanella Netto wrote:
>
>
> On 29/08/23 04:59, Florian Weimer via Libc-alpha wrote:
> > * Aurelien Jarno:
> >
> >> diff --git a/sysdeps/unix/sysv/linux/powerpc/bits/fcntl.h b/sysdeps/unix/sysv/linux/powerpc/bits/fcntl.h
> >> index f7615a447e..d8a291a331 100644
> >> --- a/sysdeps/unix/sysv/linux/powerpc/bits/fcntl.h
> >> +++ b/sysdeps/unix/sysv/linux/powerpc/bits/fcntl.h
> >> @@ -33,7 +33,7 @@
> >> # define __O_LARGEFILE 0200000
> >> #endif
> >>
> >> -#if __WORDSIZE == 64
> >> +#if __WORDSIZE == 64 && !defined __USE_FILE_OFFSET64
> >> # define F_GETLK 5
> >> # define F_SETLK 6
> >> # define F_SETLKW 7
> >
> > I find this puzzling. Why would __USE_FILE_OFFSET64 have an effect if
> > __WORDSIZE is 64?
>
> This is a historical artifact from powerpc64. Instead of following other 64-bit
> architectures and define F_GETLK the same whether _FILE_OFFSET_BITS is defined,
> the port used powerpc definitiosn that required different values to support LFS.
>
> This patch is not wrong, but at same time not really required. The powercp64
> fcntl will handle F_GETLK/F_SETLK/F_SETLKW with the historical values with
> the FCNTL_ADJUST_CMD macro, so old binaries will continue to work as expected.
It does break some binaries, for instance File-FcntlLock [1] with the
following scenario:
- perl is built against glibc 2.37
- system is upgraded to glibc 2.38
- File-FcntlLock is built against glibc 2.38: it does not work as the
value of F_GETLK has changed from 12 to 5 [2].
In short these constants are not exclusively used by the glibc. They
might be referenced in some libraries, and changing their values break
things.
[1] https://metacpan.org/dist/File-FcntlLock
[2] https://metacpan.org/release/JTT/File-FcntlLock-0.22/source/FcntlLock.xs#L74
--
Aurelien Jarno GPG: 4096R/1DDD8C9B
aurelien@aurel32.net http://aurel32.net
next prev parent reply other threads:[~2023-08-29 16:30 UTC|newest]
Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-08-28 21:37 Aurelien Jarno
2023-08-29 7:59 ` Florian Weimer
2023-08-29 13:20 ` Adhemerval Zanella Netto
2023-08-29 16:30 ` Aurelien Jarno [this message]
2023-08-29 17:06 ` Adhemerval Zanella Netto
2023-08-30 9:19 ` Andreas Schwab
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