[gst-devel] interposing / dup. symbols interest ...

Stefan Kost ensonic at hora-obscura.de
Fri Dec 16 07:07:08 CET 2005

Hi michael,

I've followed your findings a bit on your blog. When I run you
objectdump line agains some of the plugin I have in my own application I
get a rather long list. Any ideas how I can/should shorten it.
The bt_song_io_detect and *_get_type functions are the only ones that
really matters.


objdump -T ~/buzztard/lib/songio/libbtbsl.so | grep -v '\*UND'

/home/ensonic/buzztard/lib/songio/libbtbsl.so:     file format elf32-i386

00001104 l    d  .init  00000000              .init
000014e0 l    d  .text  00000000              .text
00004f34 l    d  .fini  00000000              .fini
00004f50 l    d  .rodata        00000000              .rodata
00005884 l    d  .eh_frame      00000000              .eh_frame
00006888 l    d  .ctors 00000000              .ctors
00006890 l    d  .dtors 00000000              .dtors
00006898 l    d  .jcr   00000000              .jcr
000068a0 l    d  .data.rel.ro   00000000              .data.rel.ro
00006b0c l    d  .data  00000000              .data
00006b1c l    d  .bss   00000000              .bss
000068c4 g    DO *ABS*  00000000  Base        _DYNAMIC
00001104 g    DF .init  00000000  Base        _init
00006b20 g    DO .bss   00000004  Base        bt_bsl_debug
000016d0 g    DF .text  0000004c  Base        bt_song_io_buzz_get_type
00006b1c g    D  *ABS*  00000000  Base        __bss_start
00004f34 g    DF .fini  00000000  Base        _fini
00006b1c g    D  *ABS*  00000000  Base        _edata
00006b2c g    D  *ABS*  00000000  Base        _end
000015d0 g    DF .text  00000100  Base        bt_song_io_detect

michael meeks schrieb:
> On Tue, 2005-12-13 at 14:19 +0100, Benjamin Otte wrote:
>>FWIW GStreamer uses a regex to only export [_](gst|Gst|GST)_*
>>symbols, both from core and plugins. (as you can see in his list, all
>>symbols start with gst there, so it works ;)) I'd have made it stricter
>>but couldn't in 0.8 since plugins were allowed to link to plugins back
>>then. This should have been removed by David's stuff during the 0.10
>>transition so it would be a good idea to make plugins only export
>>gst_plugin_desc in 0.10. Or am I missing something?
> 	Sure - it'd be a great idea to ensure 2 things really:
> 	a) that the plugin exports as few symbols as possible
> 		objdump -T foo.so | grep -v '\*UND' | wc -l
> 	   just 1 or two external symbols is fine as you say.
> and	b) that you g_module_open the plugin with G_MODULE_BIND_LOCAL
> 	b) of course stops other symbol lookup by applications becoming slower
> by having to examine all the plugins in the global scope. [ to test that
> use '$ LD_DEBUG=symbols gst-foo'.
> 	HTH,
> 		Michael.

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