glucose and xgl progress

[Gabor Gombas]

On Wed, Sep 19, 2007 at 10:20:49AM +0000, José Fonseca wrote:

> However, when loaded, references to __glXFreeContext *inside* 
> libglxgext.so are linked to the external __glXFreeContext in libGL.so:

If you have multiple definitions for a symbol it is completely random
which a given reference will resolve to.

Now, the two underscores are a good hint that these are internal symbols
and they should not be exported at all or if they have to, one of them
must be renamed.

> libtool's -export-dynamic flag is not being used. Using libtool's -module 
> flag doesn't change anything.

Does this symbol have to be exported? If no, you should use libtool's
--export-symbol feature to explicitely declare which symbols should be
visible and which should not. In fact, it is always wise to use
--export-symbol when creating shared libraries to prevent ABI breakage
by accidentally exporting private symbols.

If __glXFreeContext should be exported, then it should be decided which
library owns this symbol, and the other must be modified not to export
it.

If it is the case that libGL.so exports __glXFreeContext but
libglxgext.so wants to locally override it, and for some reason you
absolutely cannot rename it, then you must use gcc's
__visibility__((__protected__)) attribute when declaring __glXFreeContext
in libglgxext.so, but that is not portable to non-ELF platforms and
other compilers and also has run-time performance costs IIRC.

Gabor

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     MTA SZTAKI Computer and Automation Research Institute
                Hungarian Academy of Sciences
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