Hi,

On Windows 11, perl-5.42.0 and later, a string assignment (in XS) to an SV's PV buffer using sv_setpv can drastically reduce the value of SvLEN.

Demo: 
use strict;
use warnings;
use Devel::Peek;

use Inline C =><<'EOC';

void foo(SV * buffer) {
  char *data = "Hello there";
  sv_setpv(buffer, data);
}

EOC

my $buffer = 'z' x 60;
Dump $buffer;
foo($buffer);
Dump $buffer;

[download]
Output, running on perl-5.42.0 and perl-5.43.7: 
SV = PV(0x2352069fd80) at 0x235206db678
  REFCNT = 1
  FLAGS = (POK,IsCOW,pPOK)
  PV = 0x2352275d050 "zzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzz
+zzzzzzzzzzzz"\0
  CUR = 60
  LEN = 64
  COW_REFCNT = 1
SV = PV(0x2352069fd80) at 0x235206db678
  REFCNT = 1
  FLAGS = (POK,pPOK)
  PV = 0x2352279a8a0 "Hello there"\0
  CUR = 11
  LEN = 16

[download]
What, if anything, should I deduce from the fact that LEN has been reduced from 64 to 16.
Has the size of the PV buffer actually been reduced ?

On perl-5.40.0 and earlier, when running the same script, LEN retains its original value (which is the behaviour that I expected) : 
SV = PV(0x2076e35a3b0) at 0x2076e41b338
  REFCNT = 1
  FLAGS = (POK,pPOK)
  PV = 0x2077084ae90 "zzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzz
+zzzzzzzzzzzz"\0
  CUR = 60
  LEN = 62
SV = PV(0x2076e35a3b0) at 0x2076e41b338
  REFCNT = 1
  FLAGS = (POK,pPOK)
  PV = 0x2077084ae90 "Hello there"\0
  CUR = 11
  LEN = 62

[download]
Cheers,
Rob

In reply to [XS] sv_setpv change in behaviour with perl-5.42.0 and later by syphilis

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