[Bug stdio/26257] New: Repeated ftello calls result in lseek system calls

[Bug stdio/26257] New: Repeated ftello calls result in lseek system calls

[fweimer at redhat dot com]

https://sourceware.org/bugzilla/show_bug.cgi?id=26257

            Bug ID: 26257
           Summary: Repeated ftello calls result in lseek system calls
           Product: glibc
           Version: unspecified
            Status: NEW
          Severity: enhancement
          Priority: P2
         Component: stdio
          Assignee: unassigned at sourceware dot org
          Reporter: fweimer at redhat dot com
  Target Milestone: ---

If fseeko is never called on a stream, all ftello calls result in lseek system
calls because ftello never updates the cached file offset.

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[Bug stdio/26257] Repeated ftello calls result in lseek system calls

[carlos at redhat dot com]

https://sourceware.org/bugzilla/show_bug.cgi?id=26257

Carlos O'Donell <carlos at redhat dot com> changed:

           What    |Removed                     |Added
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                 CC|                            |carlos at redhat dot com

--- Comment #1 from Carlos O'Donell <carlos at redhat dot com> ---
(In reply to Florian Weimer from comment #0)
> If fseeko is never called on a stream, all ftello calls result in lseek
> system calls because ftello never updates the cached file offset.

It this required because the FILE handle remains inactive? Thus there is
allowed an underlying use of the file descriptor until the activating action?

See:
https://sourceware.org/glibc/wiki/File%20offsets%20in%20a%20stdio%20stream%20and%20ftell

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[Bug stdio/26257] Repeated ftello calls result in lseek system calls

[fweimer at redhat dot com]

https://sourceware.org/bugzilla/show_bug.cgi?id=26257

Florian Weimer <fweimer at redhat dot com> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |fweimer at redhat dot com

--- Comment #2 from Florian Weimer <fweimer at redhat dot com> ---
(In reply to Carlos O'Donell from comment #1)
> (In reply to Florian Weimer from comment #0)
> > If fseeko is never called on a stream, all ftello calls result in lseek
> > system calls because ftello never updates the cached file offset.
> 
> It this required because the FILE handle remains inactive? Thus there is
> allowed an underlying use of the file descriptor until the activating action?
> 
> See:
> https://sourceware.org/glibc/wiki/
> File%20offsets%20in%20a%20stdio%20stream%20and%20ftell

I don't see a compelling justification why ftello can't update the cache if the
lseek system call succeeds.

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