new thoughts on dynamic libraries support

[Lisandro Dalcin]

On Mon, Oct 20, 2008 at 10:15 PM, Barry Smith <bsmith at mcs.anl.gov> wrote:
>
>  When I added the PetscDLLibraryRegister_petscxxxx() approach
> I never fixed the pfstring to use that model.
>
>  This is all easily fixed I think, in fact adding the
> PetscDLLibraryRegister_petscxxxx()
> will likely make it better than what it was.

Yes, that would solve part of the issues, but... If we implement it in
terms of my low-level PetscDLOpen API using a PETSC_LD_LOCAL flag,
plus some careful use of mkdtemp, it could work really well, at least
on posix-like environments (I guess this does not work on Windows,
right?).

Can you see why having those PetscDLOpen/Close wrappers somewhat
exposed to other PETSc sources could be convenient? Perhaps you would
accept adding such new API to include/private/dlimpl.h ( other name
for the header? ).




>
>   Barry
>
> On Oct 20, 2008, at 5:16 PM, Lisandro Dalcin wrote:
>
>> No, Barry, I was not clear enough.
>>
>> AFAIK, PFSTRING is broken at the time you want to actually create a PF
>> of type PFSTRING. This PF type is implemented by compiling on-the-fly
>> a new dynamic library called 'libpescdlib.so' (using a template file
>> src/vec/pf/impls/string/cstringbase.c and calling 'make' via popen
>> somewhere inside $TMP dir).
>>
>> The current implementation approach has three problems:
>>
>> 1) It only works if PETSc compiled --with-dynamic. But this could work
>> even if PETSc is compiled with static libs, though that would require
>> some extra cares (users executables should be built with appropriate
>> flags for exporting symblols, like passing to the linker the flags
>> '-Xlinker -export-dynamic' when building executables).
>>
>> 2) If you look at src/vec/pf/impls/string/cstringbase.c, there is no
>> function 'PetscDLLibraryRegister_petscdlib' exported. Then the call to
>> PetscDLLibrarySym() in  FStringCreateFunction() will fail.
>>
>> 3) Even if the above issues are fixed, PETSc opens dynamic libraries
>> with RTLD_GLOBAL flags and then caches them in DLLibrariesLoaded list.
>> Then I'm not sure if this will let you create more than ONE PFSTRING.
>> If extra care is taken by using a mktemp-like routine, we still could
>> have issues with the RTLD_GLOBAL (though I'm not sure).
>>
>> As you see, the PFSTRING implementation is somewhat broken, and this
>> was never noticed because there are no tests for PFSTRING.
>>
>> BTW, You are completely right! Libraries (and specially dynamic) are
>> really overwhelming ;-)
>>
>>
>> On Mon, Oct 20, 2008 at 6:34 PM, Barry Smith <bsmith at mcs.anl.gov> wrote:
>>>
>>> On Oct 20, 2008, at 1:49 PM, Lisandro Dalcin wrote:
>>>>
>>>> PetscDLLibraryRegister_NAME. If the symbol is not exported, then
>>>> PetscDLLibraryOpen() fails!!  BTW, Because of this constraint,
>>>> PFSTRING implementation is currently broken.
>>>>
>>>
>>>  I don't understand why this would be. The PF stuff is in the Vec
>>> library.
>>>
>>> PetscErrorCode PETSCVEC_DLLEXPORT PetscDLLibraryRegister_petscvec(const
>>> char
>>> path[])
>>> {
>>> PetscErrorCode ierr;
>>>
>>> ierr = PetscInitializeNoArguments(); if (ierr) return 1;
>>>
>>> PetscFunctionBegin;
>>> /*
>>>    If we got here then PETSc was properly loaded
>>> */
>>> ierr = ISInitializePackage(path);CHKERRQ(ierr);
>>> ierr = VecInitializePackage(path);CHKERRQ(ierr);
>>> ierr = PFInitializePackage(path);CHKERRQ(ierr);
>>> PetscFunctionReturn(0);
>>> }
>>>
>>> The PF is suppose to work in the same way as the IS, I'm guessing the IS
>>> works properly?
>>>
>>> Thanks
>>>
>>>  Barry
>>>
>>>>
>>>
>>>
>>
>>
>>
>> --
>> Lisandro Dalcín
>> ---------------
>> Centro Internacional de Métodos Computacionales en Ingeniería (CIMEC)
>> Instituto de Desarrollo Tecnológico para la Industria Química (INTEC)
>> Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET)
>> PTLC - Güemes 3450, (3000) Santa Fe, Argentina
>> Tel/Fax: +54-(0)342-451.1594
>>
>
>



-- 
Lisandro Dalcín
---------------
Centro Internacional de Métodos Computacionales en Ingeniería (CIMEC)
Instituto de Desarrollo Tecnológico para la Industria Química (INTEC)
Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET)
PTLC - Güemes 3450, (3000) Santa Fe, Argentina
Tel/Fax: +54-(0)342-451.1594