-----Original Message-----
From: Niels Larsen
Sent: Friday, September 19, 2014 12:05 AM
I have not yet reported the problem and found no complaints with
Google, so maybe I missed something. Or have the Perl people
forgotten about Inline .. ?
Inline will be subject to the same behaviour as XS.
Only time I’ve been bitten by COW was doing something like this:
########################################
use strict;
use warnings;
use Inline C => Config =>
BUILD_NOISY => 1,
USING => 'ParseRegExp';
use Inline C => <<'EOC';
void change_char(char * in) {
sprintf(in, "%d", -123);
}
EOC
my $orig = 'XOXO';
my $copy = $orig;
print "$orig $copy\n";
change_char($orig);
print "$orig $copy\n";
########################################
On 5.18 and earlier, this script outputs:
XOXO XOXO
-123 XOXO
But with 5.20, when you call change_char() to alter $orig, it also alters
$copy - ie the script outputs:
XOXO XOXO
-123 -123
According to p5p, this is a misuse of the char* typemapping, which was not
intended to accommodate this type of writing, though the following (which
avoids the char* typemapping) does exactly the same thing:
void change_char(SV * in) {
sprintf(SvPV_nolen(in), "%d", -123);
}
(No doubt this is also misuse, hidden under another cloak.)
I think there are API calls one can make to avoid the problem, but I ended
up just rewriting my XS code such that whenever an XSub writes to a buffer,
it writes to a buffer that was created in XSpace (not a buffer that was
passed to it from Perl-space).
I think you'll find that any XS/Inline problems you're having with COW will
be (in the view of p5p, at least) because the XS code needs to be
rewritten - not because of some problem with COW itself.
But without seeing an actual demo of your problem, I'm only speculating.
I don't think there should *ever* be a need to make amendments to a C
library - though there may well be situations where the (XS) code that
accesses that library needs to be changed.
Cheers,
Rob
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