[GRASS-dev] [GRASS-SVN] r60054

[Glynn Clements]

Markus Metz wrote:

> > If so, I suggest changing that, however invasive it may be.
> 
> Very invasive.

Probably not. Admittedly, it would affect a lot of code, but only in
fairly trivial ways. Specifically, all of the "Map" variables would
become pointers rather than structures, calls to vector functions will
have "&Map" changed to "Map", and the open functions will return a
pointer rather than having one passed in.

Although, we could probably get away with just storing a table of
pointers. In theory, callers might move/copy the Map_info structures;
in practice, they don't.

> > I'd
> > certainly suggest holding off on any 7.0 release until that's
> > resolved.
> 
> Hmm. This sounds like synchronizing some basic concepts of the raster
> and vector libraries,

Not really; it's just fixing a design flaw in the 6.x vector API.

Apart from the issue of the vector library not having a list of open
maps, another issue is that the size (and occasionally[1] the layout)
of the Map_info structure gets baked into the modules, so anything
which changes the layout of the structure constitutes a change to the
ABI.

[1] e.g. v.info references a couple of fields directly, rather than
using the appropriate accessor functions.

Ideally, the size and layout of the Map_info structure should only be
known to the vector libraries. The public headers should declare
Map_info as an abstract structure ("incomplete type" in C parlance).

> which in turn sounds like something for GRASS 8.

FWIW, the first 6.0 beta was tagged on 2005-01-12, i.e. over 9 years
ago. Unless there's a reason to believe that 7.0->8.0 will happen
somewhat quicker than 6.0->7.0, 8.0 is too long to wait.

-- 
Glynn Clements <glynn at gclements.plus.com>