[Libreoffice] gbuild of external libraries and question about apparently special case like zlib, jpeg etc.

[Stephan Bergmann]

On Sep 4, 2011, at 11:47 PM, Norbert Thiebaud wrote:
> Now, the question is: is there any scenario where one would build the
> internal library but only use the internal library for some module and
> the system library for others?
> iow, why does the current code use a separate name for the internal
> library, like libzlib or libjpeglib ? is this really (still) needed ?
> 
> in the same vein, why is there zlib/zlib.h and external/zlib/zlib.h ?

At least with OOo, there sometimes popped up problems when OOo brought along its version of some external library, wanted to load it as a dependency of some other OOo library, but OOo also (indirectly) loaded another version of that external library from the system, through some other chain of dependency.  At least on Linux, that would result in only one of the two versions of the external library being loaded, and the other dependee failing more or less badly.

To remedy that, OOo sometimes included external libraries as static archives, sometimes renamed external libraries to non-clashing names and also used symbol versioning to make sure the dependees picked the right ones, respectively.

I do not remember where exactly which solution was used (this also changed over time), but it would probably explain some of the weirdness you see when you look at how those external modules are actually built.

-Stephan