2007.05.04 13:13 "Re: [Tiff] TIFFSetField and float values", by Toby Thain
On 4-May-07, at 10:02 AM, Joris wrote:
Oh, my, I've found the reason. Digging into the source code I realized that TIFFSetField
gets the parameter from va_arg as double:
(From tif_dir.c,v 1.72 2006/03/15 12:49:35, line 234:)
td->td_xresolution = (float) va_arg(ap, double);
When I pass argument of type double, the tag saves the value properly. Looks like an error in documentation (TIFFSetField.3tiff.html)?
I would agree... but I suspect other compilers may behave differently. I suspect that passing a float, as per documentation, would work for most, but passing a double will work for all.
In standard C, floats are always promoted to double in function arguments.
> I've also tried changing the code you quote from tif_dir.c to va_arg > (ap,float), but that doesn't work on our Borland compilers at all
(and likely it will not work on most other compilers either, I think). So I'm about to propose to change the documention to specify a double parameter as part of the next update.
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