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July 2005
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2005.07.21 14:09 "Re: question of understanding / D7 and Var-Types", by Frank Warmerdam
On 7/20/05, Joris <joris.at.lebbeke@skynet.be> wrote: > Matthias his problem got solved when we remembered > > http://www.asmail.be/msg0055048683.html > > ...we would appreciate more insight. Joris, This is a pecularity of C. When floating point (single) values are passed to a function that lacks a prototype (or uses varargs "..." as in this case) they are automatically promoted to double. So internally libtiff has to pull a double off the stack instead of a float even though it considers the field to be float. Because it considers the field to be a float, when you request the value you have to pass a float*, not a double*. Developers in C don't see this issue since the compiler converts the type automatically. Best regards, -- ---------------------------------------+-------------------------------------- I set the clouds in motion - turn up | Frank Warmerdam, warmerdam@pobox.com light and sound - activate the windows | http://pobox.com/~warmerdam and watch the world go round - Rush | Geospatial Programmer for Rent