[GRASS5] r.neighbors: works with reclass maps?

[Glynn Clements]

Markus Neteler wrote:

> thanks for looking into this! Do you see a chance to work
> around?

Sure; I just need to determine how G__.work_buf, G__.mask_buf etc are
managed, and add another one.

> I have seen some malloc tests in other "configures"
> such as GDAL etc. Perhaps they have a functional autoconf
> implementation?

The issue is with alloca(). alloca() suffers from lots of
platform-specific quirks, due the fact that it has to be implemented
by the compiler.

Getting autoconf to detect its presence or absence (and implementing a
workaround if absent) is simple. It's the usage which is messy (see
the documentation of AC_FUNC_ALLOCA in the autoconf Info file for
details).

This is unfortunate, as alloca() is very useful for short-lived
variable-sized buffers. Whereas alloca() may take only a single CPU
clock cycle, malloc() and free() can take an arbitrary amount of time. 
An additional malloc/free per call to G_get_raster_row() could result
in a significant performance hit.

-- 
Glynn Clements <glynn.clements at virgin.net>