[Libav-user] ff_log2_tab defined multiple times in the fmpeg 1.1 libraries, bug or feature ??

Michael Niedermayer michaelni at gmx.at
Wed Feb 13 20:01:06 CET 2013


On Wed, Feb 13, 2013 at 04:36:38PM +0100, Lars Hammarstrand wrote:
> Hello, can someone please explain the reason (and how to cope with) that *
> ff_log2_tab* is defined multiple times with *#include "libavutil/log2_tab.c*"
> in the ffmpeg v1.1 libraries like libavcodec 54.91.102 and companions ??

duplicating the tables causes a small performance increase in some
linking configurations.

> This results in "duplicate symbols" while linking as listed below. To get
> ride of the problem we need to delete the duplicated entries by hand with
> "ar -d libxxx.a log2_tab.o" for all libraries but one, not a very smooth
> solution. Will this behavior change in the future or do weed need to
> automate a duplicate removal process while building the ffmpeg libraries
> for XBMC?

Ive posted a patch to ffmpeg-dev, which may fix this:
0213 19:51 To FFmpeg devel (3.0K) [FFmpeg-devel] [PATCH] buildsys: only include log2_tab per library for shared builds

please test and comments welcome

note, some linkers can also be configured to ignore duplicate symbols

Thanks for the bug report

Michael     GnuPG fingerprint: 9FF2128B147EF6730BADF133611EC787040B0FAB

Concerning the gods, I have no means of knowing whether they exist or not
or of what sort they may be, because of the obscurity of the subject, and
the brevity of human life -- Protagoras
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