[petsc-dev] Reminder: *every* symbol with extern linkage *must* be namespaced

[Jed Brown]

On Sat, Mar 17, 2012 at 10:49, Shri <abhyshr at mcs.anl.gov> wrote:

> I don't know namespacing but looks like its a C++ declaration that can be
> simulated in C either using prefixes or by using a struct.
> http://ejrh.wordpress.com/2012/01/24/namespaces-in-c/ .
> What's the prefered PETSc way of namespacing in C? Use the prefix 'Petsc'?
>

Yes, use prefixes for all symbols with extern linkage. (Whichever prefix is
appropriate for the class you are working with.)

If you have symbols that go togother, and especially if it might make sense
to have multiple instances, it makes sense to put them together in a
struct. There may still be a global instance of the struct (which must
itself be namespaced), but the members of the struct no longer need their
own namespace because they are not symbols (in the linker sense).

Any time you create a symbol with extern linkage, you are declaring that
nobody in the universe (defined by all code that might ever be linked into
an application that somehow calls PETSc) will ever choose that name for
themselves. PETSc already has (in my opinion) claimed more than its share
in user-visible namespace (e.g. Vec and Mat), but changing that is
obnoxious for users so it has been postponed indefinitely. There is no
excuse, however, for not namespacing new symbols or symbols that are not
public (intended for the user to interact with).
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