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Postings from December 2011
On Sun, Nov 27, 2011 at 02:53:47PM -0800, Father Chrysostomos wrote:
> #define SVf_FAKE 0x01000000 /* 0: glob or lexical is just a copy
> 1: SV head arena wasn't malloc()ed
> 2: in conjunction with SVf_READONLY
> marks a shared hash key scalar
> (SvLEN == 0) or a copy on write
> string (SvLEN != 0) [SvIsCOW(sv)]
> 3: For PVCV, whether CvUNIQUE(cv)
> refers to an eval or once only
> [CvEVAL(cv), CvSPECIAL(cv)]
> 4: On a pad name SV, that slot in the
> frame AV is a REFCNT'ed reference
> to a lexical from "outside". */
> #define SVphv_REHASH SVf_FAKE /* 5: On a PVHV, hash values are being
> recalculated */
>
> Item 0 above says ‘glob or lexical is just a copy’. What type of
> lexical would that be? Is it the same as item #4?
I strongly suspect it is.
> Are pad name SVs
> flagged somehow so they can be identified as such in isolation (e.g., in
> sv_setsv, etc.)? Is it feasible to use SvFAKE without SvREADONLY to
> indicate that SvPVX is actually the key field of a HEK, but not a shared
> one?
No, I don't think pad name SVs are detectable as such, only by virtue
of being linked from name pads. But I think it's highly restricted
in where they appear, and with a bit of code auditing you could probably
make sure sure they never appear in sv_setsv etc (I would suspect
debugging code would be the thing needing most tweaking).
--
The Enterprise's efficient long-range scanners detect a temporal vortex
distortion in good time, allowing it to be safely avoided via a minor
course correction.
-- Things That Never Happen in "Star Trek" #21
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