[GRASS-dev] graph function input limitations

[Glynn Clements]

Paulo van Breugel wrote:

> > To be honest, I'm not sure that it's worth increasing this value in
> > the standard version. 5000 arguments in a function call is rather
> > extreme, and probably a hint that alternative approaches should be
> > considered.
> 
> What are the possible disadvantages of increasing this limit?

1. We have to decide upon a limit. If ~5000 arguments isn't enough, is
10,000? 100,000? A million?

2. If someone actually uses 5000 arguments, forcing them to seek help
might be considered a good thing.

> But you are right, there aren't probably many user cases where more
> then 5000 arguments are used. And as my case illustrates, there
> might be better alternatives. In any case, would it be possible to
> change the error message when the limit is surpassed from the
> generic 'memory exhausted', to something along the lines of "maximum
> number of function arguments exceeded"?

Changing it would require a non-portable hack. The actual string is
part of the parser skeleton, which is beyond our control. For bison,
it's passed to the YY_() macro used for localisation. We could
re-implement that macro, but that would affect other localised
messages. And may cause problems for other versions of yacc.

> And possibly, this limitation could be mentioned in the help file?

The current limit is implementation-dependent, i.e. if GRASS was built
using a different version of yacc, the limit might be different. Also
YYMAXDEPTH isn't specified by POSIX, so setting it wouldn't make the
limit not implementation-dependent.

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