[Bug libc/5807] strlen() not effective

[Bug libc/5807] strlen() not effective

[roland at gnu dot org]

http://sourceware.org/bugzilla/show_bug.cgi?id=5807

Roland McGrath <roland at gnu dot org> changed:

           What    |Removed                     |Added
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         AssignedTo|roland at redhat dot com    |drepper.fsp at gmail dot
                   |                            |com

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[Bug libc/5807] strlen() not effective

[fweimer at redhat dot com]

https://sourceware.org/bugzilla/show_bug.cgi?id=5807

Florian Weimer <fweimer at redhat dot com> changed:

           What    |Removed                     |Added
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              Flags|                            |security-

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[Bug libc/5807] strlen() not effective

[drepper at redhat dot com]

------- Additional Comments From drepper at redhat dot com  2009-03-15 08:50 -------
I changed the code.  Although noboy seems to use it.

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             Status|ASSIGNED                    |RESOLVED
         Resolution|                            |FIXED


http://sourceware.org/bugzilla/show_bug.cgi?id=5807

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[Bug libc/5807] strlen() not effective

[stas dot yakovlev at gmail dot com]

------- Additional Comments From stas dot yakovlev at gmail dot com  2008-04-23 15:48 -------
Carlos,

Thanks for reply.

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[Bug libc/5807] strlen() not effective

[carlos at codesourcery dot com]

------- Additional Comments From carlos at codesourcery dot com  2008-04-22 13:03 -------
Stas,

The changes are more than trivial, you would need a copyright assignment for
glibc on file with the FSF.

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[Bug libc/5807] strlen() not effective

[stas dot yakovlev at gmail dot com]

------- Additional Comments From stas dot yakovlev at gmail dot com  2008-04-17 19:55 -------
Created an attachment (id=2703)
 --> (http://sourceware.org/bugzilla/attachment.cgi?id=2703&action=view)
Alan Mycroft's hack for strlen()

Hi All.

I know that you only accept patches if
contributor signs an assignment.

But do you accept small bug fix without an
assignment, like that I attached to the bug ?

This is a fix for strlen() only
(I can do it for all other functions if you can accept
patches like this). It deletes old comments,
and adds Alan Mycroft's hack.

Stas.


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[Bug libc/5807] strlen() not effective

[carlos at codesourcery dot com]

------- Additional Comments From carlos at codesourcery dot com  2008-03-02 15:12 -------
Note: All the string/* operations should use the corrected algorithm, and the
old comments should be removed.

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[Bug libc/5807] strlen() not effective

[carlos at codesourcery dot com]

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OtherBugsDependingO|                            |5806
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[Bug libc/5807] strlen() not effective

[carlos at codesourcery dot com]

------- Additional Comments From carlos at codesourcery dot com  2008-03-02 03:29 -------
The math is wrong. 

It looks glibc has a broken version of Alan Mycroft's HAKMEMC postings.
See: http://www.cl.cam.ac.uk/~am21/progtricks.html

The solution is "((x - 0x01010101) & ~x & 0x80808080)", but the "& ~x" is
missing from the glibc version.

The "#if 0" was added Tue Jan 21 03:39:54 1992 UTC (16 years, 1 month ago) by
roland, and the patch looked like this:
http://sources.redhat.com/cgi-bin/cvsweb.cgi/libc/sysdeps/generic/Attic/strlen.c.diff?r1=1.1&r2=1.2&cvsroot=glibc

I can reproduce this on cvs head. The generic strlen function is horribly
inefficient.

Roland can you comment on this? 

What's the legal status of using that algorithm?

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           What    |Removed                     |Added
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         AssignedTo|drepper at redhat dot com   |roland at redhat dot com
             Status|NEW                         |ASSIGNED


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