Re^3: odd line in windows

The typemap automatically creates a reference to it and returns the reference. It's refcount is off by one, though.

use strict;
use warnings;

use Devel::Peek qw( Dump );

use Inline C => <<'__EOI__';

AV* f() {
   return newAV();
}

__EOI__

Dump(f());
[download]

>perl -MInline=FORCE,NOISY,NOCLEAN a.pl
...
SV = IV(0x7bbf18) at 0x7bbf1c
  REFCNT = 1
  FLAGS = (TEMP,ROK)
  RV = 0x7bc05c
  SV = PVAV(0x7bcec8) at 0x7bc05c
    REFCNT = 2         <--- XXX
    FLAGS = ()
    ARRAY = 0x0
    FILL = -1
    MAX = -1
    ARYLEN = 0x0
    FLAGS = (REAL)
[download]

Making it mortal doesn't help. So unless I'm missing something, this can only be used if you actually hold a reference to the array you return.

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Re^4: odd line in windows by syphilis (Archbishop) on Sep 08, 2011 at 10:58 UTC
So unless I'm missing something, this can only be used if you actually hold a reference to the array you return No way to alter that particular reference count before returning the newly created AV ? Cheers, Rob	[reply]
Re^5: odd line in windows by BrowserUk (Patriarch) on Sep 08, 2011 at 11:12 UTC
According to the example in the Inline C Cookbook, the correct way to return an AV* is: `newRV_noinc( (SV*)array = newAV() )` [download] Which kind of makes sense given the info ikegami posted above. 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] [d/l]
Re^6: odd line in windows by syphilis (Archbishop) on Sep 08, 2011 at 11:29 UTC
Which kind of makes sense given the info ikegami posted above Yes, it does make sense - yet it's not what I naively expected. I expected that you'd just return the AV* ... but if that can bugger up the refcount, and there's no way of twiddling it, then one certainly needs to be careful whenever one declares a function as returning AV. Still, it was probably a silly question on my part. If there was* a way to twiddle that refcount in a returning AV*, then I would think ikegami would have mentioned it. Cheers, Rob	[reply]
Re^7: odd line in windows by BrowserUk (Patriarch) on Sep 08, 2011 at 11:58 UTC
Re^8: odd line in windows by syphilis (Archbishop) on Sep 08, 2011 at 13:24 UTC
Some notes below your chosen depth have not been shown here
Re^8: odd line in windows (names, XS) by tye (Sage) on Sep 08, 2011 at 16:51 UTC
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Re^8: odd line in windows by ikegami (Patriarch) on Sep 08, 2011 at 20:00 UTC
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Re^6: odd line in windows by ikegami (Patriarch) on Sep 08, 2011 at 21:22 UTC
`MUTABLE_SV(av)` is better `(SV*)av` because it won't cast away `const`.	[reply] [d/l] [select]
Re^5: odd line in windows (WONTFIX) by ikegami (Patriarch) on Sep 09, 2011 at 03:20 UTC
I filed a ticket and was told that this is documented in perlxs. This is quite useful as it usually improves readability. While this works fine for an `SV `, it's unfortunately not as easy to have `AV ` or `HV ` as a return value. You should* be able to write: `AV * array() CODE: RETVAL = newAV(); /* do something with RETVAL / OUTPUT: RETVAL` [download] But due to an unfixable bug (fixing it would break lots of existing CPAN modules) in the typemap file, the reference count of the `AV ` is not properly decremented. Thus, the above XSUB would leak memory whenever it is being called. The same problem exists for `HV *`.	[reply] [d/l] [select]
Re^5: odd line in windows by ikegami (Patriarch) on Sep 08, 2011 at 19:53 UTC
No. Decrementing its refcount before returning it would free it. One would normally make it a mortal, but I tried that and it didn't work.	[reply]