in reply to PV limits on 64-bit perls?

scalars don't have a length. Do you mean the string contained within a scalar? I think 64-bit lengths on builds with 64-bit IVs. However, I recently heard many builtins (index? substr?) use 32-bit indexes.

Update: Found this: 

/* Size_t:
 *    This symbol holds the type used to declare length parameters
 *    for string functions.  It is usually size_t, but may be
 *    unsigned long, int, etc.  It may be necessary to include
 *    <sys/types.h> to get any typedef'ed information.
 */
#define Size_t size_t     /* length paramater for string functions */

#define MEM_SIZE Size_t

typedef MEM_SIZE STRLEN;

    STRLEN      xpv_cur;        /* length of svu_pv as a C string */
    STRLEN      xpv_len         /* allocated size */

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I have no idea what that means, but it appears to be configurable somehow since Size_t is defined in a file called "uconfig.h".

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Re^2: PV limits on 64-bit perls?
by BrowserUk (Patriarch) on Sep 23, 2009 at 02:43 UTC
    scalars don't have a length. Do you mean the string contained within a scalar?

    That's why I said "PV" in the title.

    However, I recently heard many builtins (index? substr?) use 32-bit indexes.

    That would (almost) explain what I'm seeing. I'm returning an SV with the PV set to point at an 8GB lump of memory mapped file. I'm setting CUR and LEN myself, and length duly reflects the numbers I set. But if I try to substr that scalar with an offset > 2**31, it bellyaches about "substr outside of string". Which perhaps suggests that they are doing some signed 32-bit math with what should be unsigned 64-bit values.

    I guess I'll have to map the file as N x 2GB lumps so that they'll play nice with substr et al.

    Looks like there are still some edges to be knocked off the 64-bit ports.

    Examine what is said, not who speaks -- Silence betokens consent -- Love the truth but pardon error.
    "Science is about questioning the status quo. Questioning authority".
    In the absence of evidence, opinion is indistinguishable from prejudice.
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      But if I try to substr that scalar with an offset > 2**31, it bellyaches about "substr outside of string"

      Heh ... on the x64 build of ActivePerl (perl-5.10.1, build 1006): 
      C:\>perl -we "print substr 'hello', (2 ** 32)+$_, 1 for 0..4"
hello

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      Cheers,
      Rob
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[d/l]

        You 'ad me goin' there for a sec :) A very neat demo of the problem!

        Examine what is said, not who speaks -- Silence betokens consent -- Love the truth but pardon error.
        "Science is about questioning the status quo. Questioning authority".
        In the absence of evidence, opinion is indistinguishable from prejudice.
[reply]

      In bleed, I see I32 in pp_substr: 

      I32 pos;
I32 rem;
I32 fail;

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      It doesn't take much imagination to figure out how those vars are surely used. Right off the bat, one of the args is placed in pos: 

      pos = POPi;

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[d/l]
[select]

        That'd do it. Thanks for your research. That reference and syphilis' testcase make a pretty good bug report I think.

        Examine what is said, not who speaks -- Silence betokens consent -- Love the truth but pardon error.
        "Science is about questioning the status quo. Questioning authority".
        In the absence of evidence, opinion is indistinguishable from prejudice.
[reply]

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