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Re: [PATCH] Math::BigInt::FastCalc v0.15
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From:
Tels
Date:
May 28, 2007 05:16
Subject:
Re: [PATCH] Math::BigInt::FastCalc v0.15
Message ID:
200705281402.41683@bloodgate.com
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Moin,
On Monday 28 May 2007 09:57:27 Nicholas Clark wrote:
> On Sun, May 27, 2007 at 02:43:15PM +0000, Tels wrote:
> > Another oddity I noticed is that for magic strings (like matches coming
> > out of the regexp engine), the following failed under v5.8.8:
> >
> > SvPV(x, len); /* convert to string & store length */
> > cur = SvEND(x); /* points to \0 instead */
> >
> > This solves it:
> >
> > cur = SvPV(x, len); /* convert to string & store length */
> > cur += len;
> >
> > However, I am not sure is this a bug in Perl or just my poor
> > understanding of XS.
>
> I don't know for sure, either.
> If you add
>
> sv_dump(x);
>
> at that point, what is the dump output for one of the magic strings?
Oh, this problem can only be reproduced if I put in the code that caused
parts inside Calc to get BigInts (so it doesn't happen in the normal
FastCalc testsuite). But with that code, the follow perl snipped triggers
it:
use Math::BigFloat;
$x = Math::BigFloat->new('0.008'); $y = Math::BigFloat->new(29);
$x->bdiv(3,$y);
And this:
end = SvPV(x, len);
end += len;
cur = SvEND(x);
if (end != cur)
{
printf ("end: %p, cur: %p\n", cur, end);
sv_dump(x);
}
produces this:
# perl -Ilib -Iblib/arch t.pl
end: 0xb16ac0, cur: 0x669a32
SV = PVIV(0x9c7d20) at 0x786590
REFCNT = 1
FLAGS = (PADBUSY,PADMY,ROK,OVERLOAD)
IV = 0
RV = 0xb16ac0
PV = 0xb16ac0 ""
CUR = 0
LEN = 0
Argument "\0\0" isn't numeric in addition (+)
at /usr/lib/perl5/5.8.8/Math/BigInt/Calc.pm line 281.
end: 0xb16ac0, cur: 0x669a12
SV = PVIV(0x9c7d20) at 0x786590
REFCNT = 1
FLAGS = (PADBUSY,PADMY,ROK,OVERLOAD)
IV = 0
RV = 0xb16ac0
PV = 0xb16ac0 ""
CUR = 0
LEN = 0
Argument "\0\0" isn't numeric in numeric eq (==)
at /usr/lib/perl5/5.8.8/Math/BigInt/Calc.pm line 304.
Hm. So I should have checked for SvPOK() before accessing SvEND() I guess.
OTOH, how is my XS code supposed to handle an overloaded string, anyway?
Best wishes,
Tels
- --
Signed on Mon May 28 13:55:41 2007 with key 0x93B84C15.
View my photo gallery: http://bloodgate.com/photos
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