new thoughts on dynamic libraries support

[Barry Smith]

On Oct 20, 2008, at 1:49 PM, Lisandro Dalcin wrote:

> After thinking hard how to follow Barry's concerns about "not add new
> stuff", perhaps we could do things as to make 'private' the
> PetscDLOpen/PetscDLClose low-level wrappers to platform's DLL API's.
> But this would requiere some small changes to the way
> PetscDLLibraryOpen() currently works.
>
> For PetscDLLibraryOpen() to success, the dynamic library currently
> have two requisites:
>
> 1) The library must me named libNAME[.???] , i.e. the filename must
> begin with 'lib' prefix, but the extension (eg: .so / .dll / whatever)
> is optional !!. If the filename does not start with 'lib', then
> PetscDLLibraryOpen() fails!!.

    It is fine to make the lib optional.
>
>
> 2) The dynamic library must export a function
> PetscDLLibraryRegister_NAME. If the symbol is not exported, then
> PetscDLLibraryOpen() fails!!

    This is also ok, but in a PetscInfo() warning if it does not have  
such a
symbol.

>  BTW, Because of this constraint,
> PFSTRING implementation is currently broken.
>
> If Barry agree to make (1) and (2) optional (perhaps making
> appropriate PetscInfo calls), then I would accept to make my new
> PetscDLOpen/PetscDLClose stuff truly private to the src/sys/dll
> directory.
>
> If (1) and (2) are not made optional, then the PetscDLLibraryXXX() API
> is not general enough. It would not be possible to dlopen almost any
> library unrelated to PETSc. But PetscDLLibraryXXX() has some other
> nice features, like automatic file retrieval, and automatic
> register-in-linked-list of oppened libraries, that it would be great
> to make this higher-level API usable in more general cases.
>
>
>
>
> -- 
> 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
>