[fpc-devel] size of extended

[Jonas Maebe]

On 31 Oct 2009, at 01:14, peter green wrote:

> 1: is there a table anywhere of the size of extended on different  
> platforms?

No.

> 2: the mentions of m68k (which was dropped a while back afaict) and  
> very little else in the manual makes me suspect the manual in  
> general may be rather outdated.

The section on floating point precision might be. Extrapolating from  
that to the entire manual is a bit of a stretch. m68k support also  
hasn't been dropped as in "we won't ever support that anymore" (as  
opposed to e.g. go32v1 support), and at least one person occasionally  
works on fixing the m68k support in the compiler again. Removing all  
references now and possibly adding them again later does not seem like  
a useful exercise.

> 3: afaict x64 appears to have true extended yet the text strongly  
> implies that x86 is the only architecture that does.

x86_64 supports 80 bit extended on some OSes, see http://bugs.freepascal.org/view.php?id=14874

In general, it's a bad idea to depend on extended being of any  
particular size. Simply assume that sizeof(extended) >= sizeof 
(double). If you need more than double precision, use a specialised  
library (unless you are only interested in i386 support).


Jonas