[petsc-dev] Symbol visibility

[Barry Smith]

On Dec 6, 2010, at 11:53 AM, Jed Brown wrote:

> I'm not convinced that removing the PETSCXXX_DLLEXPORT stuff was a good thing.  Besides the obvious issues on Windows, it removes the ability to do proper export control.  This is discussed at length in section 2.2:
> 
> http://www.akkadia.org/drepper/dsohowto.pdf#page=17
> 
> but the tangible benefit is that distro packagers would be happier because it allows more robust handling of dependencies.  I realize that it was unused, but the "export" label has real meaning (even if only as documentation at this point) in a library context.  Most internal functions can (and should) be static, but there are a few that need more than file scope, but still shouldn't be exported.
> 
> I understand that it's one more thing, and perhaps the simplicity is worth it, but I wanted to point out that with those macros, we could have used (gcc/clang/intel) -fvisibility=hidden and defined the macro to __attribute__((visibility("default"))).
> 
> Jed

  Worse comes to worse I put it back (but better next time :-).

  Actually I think handling these "things" with CPP is not the way to go, in fact, I'd like to see, if possible, almost no use of CPP in PETSc source. Reason: PETSc source code currently is the combination of two relatively simple but very different, languages CPP and C. Doing source to source manipulations on this beast is a nightmare because one cannot even parse CPP plus C. If we eliminate the CPP then it becomes only C which we parse and manipulate relatively easily, this opens up enormous opportunities for a whole new approach to code development we do not have currently and cannot have with a CPP plus C code base. Of course, I could be totally on the wrong track but I won't know without investigation.

  Honestly I am sick of having this big code base where making changes means editing flat files and manually changing source code, I thinking that model really needs to change. I don't really know how to change the model but I really want to see if change and if that involves going down some wrong roads that is ok with me, better than not trying things.

  Barry