[Gdal-dev] Re: Adding const to OGR geometry classes?

[Frank Warmerdam]

Ben Discoe wrote:
> Hi Frank,
> 
> I have been forging ahead with the plan to make heavier use of the OGR
> geometry classes as replacements for the old, simple geometry classes the
> VTP currently uses.
> 
> This means i've been starting to use classes like OGRPolygon directly for my
> own storage and methods, rather than just as a means to use OGR as a format
> reader.
> 
> Here is one thing i've encountered.  How would you feel about adding 'const'
> as appropriate in methods that won't modify what they're passed.
> 	e.g.
> << OGRLinearRing::OGRLinearRing( OGRLinearRing * );
> 
>>>OGRLinearRing::OGRLinearRing( const OGRLinearRing * );
> 
> 
> <<    void   OGRPolygon::addRing( OGRLinearRing * );
> 
>>>   void   OGRPolygon::addRing( const OGRLinearRing * );
> 
> 
> If you have no objections, i'd be happy to make the changes and submit them
> to you.  I can play it conservatively, only using const where it's entirely
> unambiguous.

Ben,

I realize this would be a good idea for a clean C++ interface.  However, any
constness changes alter the C++ signatures and this gives me no end of
headaches from OGR uses trying to use slightly updated OGR shared libraries
with precompiled applications using OGR.  After getting burned painfully
with previous const correctness changes you suggested in OGRSpatialReference,
I have been hesitant to apply more.

Recently I have actually been encouraging applications to use the OGR C API
to reduce the tie-age to a specific GDAL/OGR build.

I am cc:ing this to the gdal-dev list to collect other opinions on whether
const correctness changes are worth the pain.  I realize it isn't clean, but
the issue is just whether you need to cast away the constness in your
application level code, right?

Best regards,

-- 
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I set the clouds in motion - turn up   | Frank Warmerdam, warmerdam at pobox.com
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and watch the world go round - Rush    | Geospatial Programmer for Rent