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From: Corinna Vinschen <vinschen@redhat.com>
To: newlib@sourceware.org
Subject: Re: [PATCH] newlib: fix fseek optimization with SEEK_CUR
Date: Wed, 13 Nov 2019 10:15:00 -0000	[thread overview]
Message-ID: <20191113101528.GQ3372@calimero.vinschen.de> (raw)
In-Reply-To: <20191109162804.1905160-1-bastien.bouclet@gmail.com>

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Hi Bastien,

On Nov  9 17:28, Bastien Bouclet wrote:
> The call to fflush was invalidating the read buffer, preventing relative
> seeks to positions that would have been inside the read buffer from
> being optimized. The call to srefill would then re-read mostly the same
> data that was initially in the read buffer.

I checked this against upstream BSD versions.  OpenBSD and NetBSD
operate like our code, including the flush, while FreeBSD uses its
internal ftello and never flushed since the repository import back in
1994.

I'm pretty unsure if we can do this.  Apparently the flush op is only
necessary for streams in append mode.  If at all.

Can we be sure this works as desired on append streams as well?

Also, given that this is changing very basic code, nobody is unaffected.
Any input from other folks?


Thanks,
Corinna

-- 
Corinna Vinschen
Cygwin Maintainer
Red Hat

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  reply	other threads:[~2019-11-13 10:15 UTC|newest]

Thread overview: 5+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-11-09 16:28 Bastien Bouclet
2019-11-13 10:15 ` Corinna Vinschen [this message]
2019-11-18 10:11 ` Corinna Vinschen
2020-01-29 18:02   ` Corinna Vinschen
2019-11-13 20:36 Bastien Bouclet

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