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Postings from May 2015
On Wed, May 27, 2015 at 09:17:21AM +0200, H.Merijn Brand wrote:
> http://www.perlmonks.org/?node_id=1127889
Which is that in 5.20.0 onwards, this:
use List::Util qw{ first };
my %hash = ( ASD => 1, ZXC => 2, QWE => 3, TYU => 4);
print first { lc $_ eq 'qwe' } keys %hash;
prints "qwe" rather than "QWE".
It bisects to this:
commit 5cd5e2d6301836ca9b0f94e9a100e697bd374cd8
Author: Father Chrysostomos <sprout@cpan.org>
AuthorDate: Wed Jan 1 05:51:36 2014 -0800
Reënable in-place lc/uc
It used to be that this code:
for("$foo") {
lc $_;
...
}
I think the logic is flawed in lc/uc/etc that does (as an optimisation)
an in-place modification of the arg and return that value, rather than
copying, when it thinks that the arg is a temporary that wont otherwise
be used again.
The arg passed to lc in the first() code block above is
SV = PV(0xa8ac28) at 0xaaa2d0
REFCNT = 1
FLAGS = (TEMP,POK,IsCOW,pPOK)
PV = 0xaa3c78 "ZXC"
CUR = 3
LEN = 0
which satisfies the 'in-place' test of
if ( ( SvPADTMP(source)
|| ( SvTEMP(source) && !SvSMAGICAL(source)
&& SvREFCNT(source) == 1 )
)
&& !SvREADONLY(source) && SvPOK(source)
&& !DO_UTF8(source)) {
So I don' think that condition is strong enough, and I'm not sure that
that there is such a safe condition.
--
Please note that ash-trays are provided for the use of smokers,
whereas the floor is provided for the use of all patrons.
-- Bill Royston
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