[postgis-devel] lwgeom parser robustness and niceness

[strk]

On Mon, Jun 07, 2004 at 09:03:40AM -0400, Carl Anderson wrote:
> strk wrote:
> >I've been testing lwgeom stuff.
> >I've found it fault on every 'unexpected' format.
> >
> >All these queries kill the backend:
> >
> >        -- EMPTY geoms
> >        SELECT 'POINT()'::lwgeom;
> >        SELECT 'MULTIPOINT()'::lwgeom;
> >        SELECT 'LINESTRING()'::lwgeom;
> >        SELECT 'MULTILINESTRING()'::lwgeom;
> >        SELECT 'POLYGON()'::lwgeom;
> >        SELECT 'MULTIPOLYGON()'::lwgeom;
> >        SELECT 'GEOMETRYCOLLECTION()'::lwgeom;
> >
> >        -- NON geoms (a check for first letter is performed)
> >        SELECT 'P()'::lwgeom
> >        SELECT 'L()'::lwgeom
> >        SELECT 'M()'::lwgeom
> >        SELECT 'G()'::lwgeom
> >
> >        -- INVALID geoms
> >        SELECT 'POINT(0 0 0 0 0)'::lwgeom;
> >        SELECT 'LINESTRING(0 0)'::lwgeom;
> >        SELECT 'POLYGON((0 0, 1 1))'::lwgeom;
> >        SELECT 'POLYGON(0 0)'::lwgeom;
> >        ... try your own ...
> >
> >        -- MIXED dimension geoms
> >        SELECT 'MULTIPOINT(0 0 0, 0 0)'::lwgeom;
> >        SELECT 'LINESTRING(0 0 0 0, 0 0 0)'::lwgeom;
> >        ... try your own ...
> >
> >Also, I don't like this error message:
> >
> >	SELECT 'point(0 0)'::lwgeom;
> >	ERROR:  couldnt determine if input lwgeom is WKB or WKT
> >
> >I think 1) it's clearly a WKT and 2) we could accept lower or mixed case
> >lwgeoms, wouldn't it be acceptable in speed ?
> >
> >--strk;
> 
> If you edit the bison/lex files to include rules that cover the above 
> cases the abends stop.  Not that this is the corrent fix just evidence 
> that it is in bison/flex
> 
> such as in wktparse.y
> from
> a_point: point_2d | point_3d | point_4d;
> 
> to include a rule for POINT()
> a_point: empty | point_2d | point_3d | point_4d;
> 
> 
> 
> I am not very good with bison/flex but
> I suspect that the parser code is emitting a warning that is tripping
> Postgres.  I have poked at the passed in error function But I think I 
> would need to RTFM first.

I suspect unallocated memory access actually... 

Ralph, could you produce a simple test app parsing WKT from stdin
and dumping WKT to stdout ?

> 
> 
> btw
> moving Makefile to
> 
> 	$(YACC) -vd -b wktparse -p lwg_parse_yy wktparse.y
> 
> causes it to produce wktparse..tab.c and wktparse.tab.h directly

Before adding switches $(YACC) compatibilities should be checked.
I belive postgresql guys to be aware of this, and they rename
the output...

--strk;

> 
> 
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