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Revision 668 - Directory Listing
Modified Sat Mar 25 13:27:27 2006 UTC (13 years, 3 months ago) by robwdcock
+ finally figured out why the tests failed when the python extension libs were
  no longer sym links. The original setup for python extension modules was to
  have sym links in the esys/* directories named, for example escriptcpp.so.
  These would link to the actual libraries libescriptcpp.so. The lib*.so would
  link to each other. When you replaced the symlink with a copy of the lib*.so
  but renamed without the lib you would then get problems. In particular,
  py_tests would suddenly start failing.

  The problem appears (I've not been able to find documentary evidence to this
  case) to be that when, for example, you import bruce, brucecpp.so imports
  lib/libescriptcpp.so (which intialises escript python bits), bruce then
  imports escriptcpp.so (which also initialised escript python bits).

  Whether that is exactly correct or not is of interest but the important bit
  is you appear to get two versions. After thinking about this for a bit and
  reviewing a bunch of other examples of working python modules I noticed a
  pattern. NONE of the other examples ever included more than the python
  wrapper code in the python extension library. Instead they just link to
  the pure C++ library. This would avoid the duplicate load.

  So, I've refactored the code. If you consider escript the pattern in now:
  lib/libescript.so - which has all of escript EXCEPT the python escriptcpp.cpp
  esys/escript/escriptcpp.so - which has ONLY the escriptcpp.cpp and links to
                               lib/libescript.so
  
  Run the tests and low and behold they all pass again.

  Q: Why doesn't this problem occur with sym links?
  A: My guess is that python and the dynamic linker take a look at the actual
     absolute python of libraries to determine if its a "different" library.
     I did fine some discussions that seem to suggest this.

  Q: Why can't you just set LD_LIBRARY_PATH==PYTHONPATH and stick all the
     libs in that directory?
  A: I (in fact we, Peter Hornby was there) tried. With the renaming of the
     python module so it doesn't have a lib prefix you get problems with
     getting the shared libraries to be looked up in LD_LIBRARY_PATH. Do
     the opposite and use lib on the python modules and you have problems
     with windows which doesn't prepend the lib. Various combination
     in between were also tried but you end up in a catch 22 situation so far
     as I could tell

  Please if you know more about the ins and outs of python and shared
  libraries let me know if this isn't true. I'd really like to know if my
  guesses are correct. In any event, the fix is more consistent with the
  patterns I've seen

  Phew! this was a long log message, glad it is on a branch!




Revision 667 - Directory Listing
Modified Fri Mar 24 13:25:00 2006 UTC (13 years, 3 months ago) by robwdcock
+ OUCH ARGHH
+ Okay the wizzy linkHack doesn't work. Not sure why but py_tests fail
when the shared library is on the link line directly (without a -l)

+ Unfortunately we can't figure out how to use -l without it prepending
a lib prefix. Hence all the shareable objects in python now need to be
called libblah.so (and lib will need to be prepended on windows!!!!).
This is not the python way and its very annoying. Why do we have this
problem? Because the C++ shared libraries link with each other.



Revision 666 - Directory Listing
Modified Fri Mar 24 11:29:40 2006 UTC (13 years, 3 months ago) by robwdcock
+ Fix up python esys area:
  + libraries are named without lib prefix on posix platforms (python standard)
  + libraries are now installed into the pyinstall area (python standard)
  + symlinks removed, no longer required
  + LD_LIBRARY_PATH is now optional for PYTHON programs (still required for c++)
+ lib PREFIX removal NOTES:
  + removing the lib prefix is non-standard for the linker. As such we've created a
    custom function sharedLinkHack to specify the .so on the link command line
    (as opposed to using -l<archive> which will prepend the lib). This has a
    a small slight of hand for scons which was being to "helpful". Scons
    verifies that when creating a shared libray all objects specified are
    created shareable (e.g. ensure objects are compiler with -fPIC). Since
    we are linking a .so out of the blue we had to wrap it up in a File note
    and flag it as shared.
    Easily done, once you know how. Thankfully this is all wrapped
    up in a simple function (sharedLinkHack) that looks like ordinary scons so
    you will never know!
    



Revision 622 - Directory Listing
Modified Wed Mar 22 14:00:08 2006 UTC (13 years, 3 months ago) by robwdcock
Creating a private branch so I can test and verify cross-platform build

Revision 279 - Directory Listing
Modified Wed Nov 30 05:23:09 2005 UTC (13 years, 7 months ago) by jgs
Original Path: trunk/esys
links to esys shared libraries


Revision 278 - Directory Listing
Modified Wed Nov 30 05:22:00 2005 UTC (13 years, 7 months ago) by jgs
Original Path: trunk/esys
__init__.py file for the esys python modules


Revision 155 - Directory Listing
Modified Wed Nov 9 02:02:19 2005 UTC (13 years, 8 months ago) by jgs
Original Path: trunk/esys
Copied from: trunk/esys2/esys revision 154
move all directories from trunk/esys2 into trunk and remove esys2


Revision 149 - Directory Listing
Modified Thu Sep 1 03:31:39 2005 UTC (13 years, 10 months ago) by jgs
Original Path: trunk/esys2/esys
Merge of development branch dev-02 back to main trunk on 2005-09-01


Revision 130 - Directory Listing
Modified Fri Jul 22 05:20:58 2005 UTC (13 years, 11 months ago) by jgs
Original Path: trunk/esys2/esys
restructured python install directory


Revision 102 - Directory Listing
Added Wed Dec 15 07:08:39 2004 UTC (14 years, 7 months ago) by jgs
Original Path: trunk/esys2/esys
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