Re: XS and -Duse64bitint

You could add an explicit conversion to IV, e.g.

     ...
     char * str;

     sv_setiv(integer, SvIV(integer));  //  <--- here
     str = SvPV_nolen(integer);
     ...
[download]

However, when doing that, I get (note the difference in the last two digits):

IV: 144115188075868217
IV: 144115188075868224
[download]

I suppose this is due to the insufficient precision in the NV representation... Actually, I think it's too late to deal with this within your XS routine, as the value will already have been converted to NV when the SV gets passed to foo() - unless you use integer on the Perl side (but you already figured that out :)

Comment on Re: XS and -Duse64bitint Select or Download Code

Replies are listed 'Best First'.
Re^2: XS and -Duse64bitint by syphilis (Archbishop) on Feb 13, 2007 at 23:00 UTC
I suppose this is due to the insufficient precision in the NV representation Yes, you're right - the precision has been lost. I was fooled by the fact that the following tests re $x (the IV) and $y (the NV) return "true": `$x == $y $x - 1 == $y - 1 $x + 1 == $y + 1` [download] I took that to indicate that perl knows that $y contains the value 144115188075868217, and that my problem was merely one of how to get at that value. The following tests also return "true": `$x == $y + 1 $x == $y - 1` [download] which doesn't fit too well with the hypothesis that "no precision was lost" :-) Thanks almut, for setting me straight. Cheers, Rob	[reply] [d/l] [select]

Replies are listed 'Best First'.

Re^2: XS and -Duse64bitint
by syphilis (Archbishop) on Feb 13, 2007 at 23:00 UTC

I suppose this is due to the insufficient precision in the NV representation

$x == $y
$x - 1 == $y - 1
$x + 1 == $y + 1
[download]

$x == $y + 1
$x == $y - 1
[download]

almut

[reply]
[d/l]
[select]