Re: memory "release" with $#=-1

I don't know if this test is conclusive, but from the result of the following script, it looks like the answer to your question is "no":
use strict; use warnings; my @x = 1..10; print '@x is at ', \@x, "\n"; $#x = -1; my @y = 1..5; print '@y is at ', \@y, "\n"; print '@x is at ', \@x, "\n"; __END__ @x is at ARRAY(0x8165ccc) @y is at ARRAY(0x8183ab0) @x is at ARRAY(0x8165ccc)
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Update: OK, so the script above is not conclusive, as ikegami points out (in fact, as it turns out, it leads to the wrong conclusion).

Devel::Peek is a better tool to answer this question. With the better information I must reject my earlier hypothesis: the answer is "yes" (i.e. space does get reused).

Note that memory location 0x811b400 originally occupied by $x[ 0 ], is occupied by $y[ 0 ] afterwards.

use strict;
use warnings;

use Devel::Peek;

my @x = 1..3;

print "Dump of \@x:\n";
Dump \@x;

$#x = -1;

my @y = 1;
print "\nDump of \@y:\n";
Dump \@y;
print "\nDump of \@x:\n";
Dump \@x;

__END__
Dump of @x:
SV = RV(0x8138618) at 0x811b574
  REFCNT = 1
  FLAGS = (TEMP,ROK)
  RV = 0x8128d68
  SV = PVAV(0x811c904) at 0x8128d68
    REFCNT = 2
    FLAGS = (PADBUSY,PADMY)
    IV = 0
    NV = 0
    ARRAY = 0x8154d00
    FILL = 2
    MAX = 3
    ARYLEN = 0x0
    FLAGS = (REAL)
    Elt No. 0
    SV = IV(0x81286a8) at 0x811b400
      REFCNT = 1
      FLAGS = (IOK,pIOK)
      IV = 1
    Elt No. 1
    SV = IV(0x81286ac) at 0x811b4b4
      REFCNT = 1
      FLAGS = (IOK,pIOK)
      IV = 2
    Elt No. 2
    SV = IV(0x81286a4) at 0x811b538
      REFCNT = 1
      FLAGS = (IOK,pIOK)
      IV = 3

Dump of @y:
SV = RV(0x8138618) at 0x811b4b4
  REFCNT = 1
  FLAGS = (TEMP,ROK)
  RV = 0x8144dc8
  SV = PVAV(0x811c95c) at 0x8144dc8
    REFCNT = 2
    FLAGS = (PADBUSY,PADMY)
    IV = 0
    NV = 0
    ARRAY = 0x814abd8
    FILL = 0
    MAX = 3
    ARYLEN = 0x0
    FLAGS = (REAL)
    Elt No. 0
    SV = IV(0x81286a8) at 0x811b400
      REFCNT = 1
      FLAGS = (IOK,pIOK)
      IV = 1

Dump of @x:
SV = RV(0x8138618) at 0x811b4b4
  REFCNT = 1
  FLAGS = (TEMP,ROK)
  RV = 0x8128d68
  SV = PVAV(0x811c904) at 0x8128d68
    REFCNT = 2
    FLAGS = (PADBUSY,PADMY)
    IV = 0
    NV = 0
    ARRAY = 0x8154d00
    FILL = -1
    MAX = 3
    ARYLEN = 0x811b574
    FLAGS = (REAL)
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the lowliest monk

Comment on Re: memory "release" with $#=-1 Select or Download Code

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Re^2: memory "release" with $#=-1 by ikegami (Patriarch) on Jun 28, 2005 at 15:33 UTC
Your snippet doesn't prove anything. It doesn't say anything about the elements of @x and @y, just @x and @y themselves. Perl arrays are objects of sorts with pointers to structures containing the actual elements.	[reply]