#define XXXType const char* ----> #define XXXType char* ?

[Lisandro Dalcin]

On 6/23/08, Barry Smith <bsmith at mcs.anl.gov> wrote:

> > typedef char const* VecType;
> >
>    No, because I do not want the const in the VecType!!!!!

I believe you did not get it ;-). The const is not on the VecType, but
in the buffer, 'const' is places before the asterisk !! In short,

typedef char const* VecType; (1)

is NOT the same as

typedef char* const VecType; (2)

In particular (1) should be completelly equivalent to

typedef const char* VecType;

and then is what you want. Try it yourserlf, please...

>  The entire reason for this discussion is to remove the const from VecType.
>

Granted, but having to push such a change just because a compiler
behaves extrangely is not the best thing to do IMHO. If we can just
find a way that make your compiler happy, then that would be the best
thing to do.

Anyway, if you decide to push the fix, at leat let me know if the
option (1) works with your compiler, just because I'll have to manage
this change in the compatibility layers of petsc4py supporting
previous PETSc releases...


> > >
> > > > Barry, I do not understand what's going on with your compiler. Perhaps
> > > > my GCC is too old? (even when -Wwrite-strings is being passed ??)
> > > >
> > > > I've just changed the '#define' and used the 'typedef', and PETSc
> > > > compile (configure.py ... && make) just passed without any warning...
> > > > Furthermore, 'make test' 'make testexamples' also passed just fine.
> > > >
> > > > Perhaps my brain is not working well, but I do not see why all this is
> > > > an issue as long as the base PetscObject structure says 'char*
> > > > type_name'.
> > > >
> > > > You can always build on a 'char*' (note: non-const) buffer what you
> > > > want, and pass it to VecSetType(), or perhaps just replace 'type_name'
> > > > in internal PETSc code.
> > > >
> > > > IMHO, user-level PETSc interface should be simple, even if that iff
> > > > internally PETSc has to relax a bit the rules (ie. using a 'char*'
> > > > variable instead of a 'MatType' variable to build something like the
> > > > "seqsbaij" string from its pieces "seq", "s", "b", "aij").
> > > >
> > > > Am I missing something? What do you actually want to do with
> 'type_name'?
> > > >
> > > > On 6/23/08, Barry Smith <bsmith at mcs.anl.gov> wrote:
> > > >
> > > >
> > > > >
> > > > >
> > > > > > Mmm, just a bit ugly you have to add the 'const' keyword. I
> insist:
> > > > > > What would be the problem with ... ??
> > > > > >
> > > > > > typedef const char* VecType;
> > > > > >
> > > > > >
> > > > > >
> > > > >
> > > > > Two problems.
> > > > >
> > > > > The VecType is a const which means one cannot build them on the fly
> and
> > > > > copy into them etc
> > > > >
> > > > > Second with the typedef one cannot do all the string manipulation on
> > > > >
> > > >
> > > them.
> > >
> > > >
> > > > > For example even the
> > > > > PetscStrcpy() in PetscHeaderCreate_Private() of type_name does not
> work.
> > > > >
> > > > > It would be nice to use a typedef instead of a define to build it
> but
> > > > >
> > > >
> > > it
> > >
> > > >
> > > > > looks impossible. (Try it,
> > > > > just change one of them and try to compile PETSc, the screaming is
> > > > > relentless.)
> > > > >
> > > > > Barry
> > > > >
> > > > >
> > > > > On Jun 23, 2008, at 2:38 PM, Lisandro Dalcin wrote:
> > > > >
> > > > >
> > > > >
> > > > >
> > > > > > On 6/23/08, Barry Smith <bsmith at mcs.anl.gov> wrote:
> > > > > >
> > > > > >
> > > > > >
> > > > > > >
> > > > > > > A while ago I made XXType (MatType, VecType etc) const char*
> > > > > > >
> > > > > > >
> > > > > > >
> > > > > > >
> > > > > >
> > > > > > Well, you actually did
> > > > > >
> > > > > > #define VecType const char*
> > > > > >
> > > > > > instead of
> > > > > >
> > > > > > typedef const char* VecType;
> > > > > >
> > > > > > which IMHO is the right way.
> > > > > >
> > > > > >
> > > > > >
> > > > > >
> > > > > > > I now think that was a mistake.
> > > > > > >
> > > > > > >
> > > > > > >
> > > > > >
> > > > > > Yep, the '#define' way can cause problems ;-)
> > > > > >
> > > > > >
> > > > > >
> > > > > >
> > > > > >
> > > > > > > I'd like to change them to just  char*
> > > > > > >
> > > > > > >
> > > > > > >
> > > > > >
> > > > > > But why not the 'typedef' way ??
> > > > > >
> > > > > >
> > > > > >
> > > > > >
> > > > > > > Can anyone suggest a technical reason why this is a bad idea
> before
> > > > > > >
> > > > > >
> > > > >
> > > >
> > > I
> > >
> > > >
> > > > >
> > > > > >
> > > > > > >
> > > > > > >
> > > > > >
> > > > > >
> > > > > push
> > > > >
> > > > >
> > > > > >
> > > > > >
> > > > > > > the code?
> > > > > > >
> > > > > > > Note this means if you have code like
> > > > > > >
> > > > > > > VecType t = VECMPI;
> > > > > > >
> > > > > > > you would need to change it to
> > > > > > >
> > > > > > > const VecType t = VECMPI;
> > > > > > >
> > > > > > >
> > > > > > >
> > > > > > >
> > > > > >
> > > > > >
> > > > > >
> > > > > > --
> > > > > > 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
> > > >
> > > >
> > > >
> > >
> > >
> > >
> >
> >
> > --
> > 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