in reply to perl5.10 Devel::Size behaviour changed?

I get: 
>c:\progs\perl580\bin\perl test.pl
SIZE : 268

>c:\progs\perl588\bin\perl test.pl
SIZE : 268

>c:\progs\perl5100\bin\perl test.pl
SIZE : 312

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4.4 bytes per element.

Or I loop 100 times: 

>c:\progs\perl580\bin\perl test.pl
SIZE : 2156

>c:\progs\perl588\bin\perl test.pl
SIZE : 2156

>c:\progs\perl5100\bin\perl test.pl
SIZE : 2200

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Still only 44 extra bytes. So they're tied to the array, not the elements. Adding Devel::Peek to the mix: 

>c:\progs\perl588\bin\perl test.pl
SIZE : 2156
SV = RV(0x185d34c) at 0x1820714
  REFCNT = 1
  FLAGS = (TEMP,ROK)
  RV = 0x236da4
  SV = PVAV(0x23bfcc) at 0x236da4
    REFCNT = 2
    FLAGS = (PADBUSY,PADMY)
    IV = 0
    NV = 0
    ARRAY = 0x18799ac
    FILL = 99
    MAX = 123
    ARYLEN = 0x0
    FLAGS = (REAL)

>c:\progs\perl5100\bin\perl test.pl
SIZE : 2200
SV = RV(0x1950668) at 0x195065c
  REFCNT = 1
  FLAGS = (TEMP,ROK)
  RV = 0x1829944
  SV = PVAV(0x23a120) at 0x1829944
    REFCNT = 2
    FLAGS = (PADMY,RMG)
    MAGIC = 0x1823f0c
      MG_VIRTUAL = &PL_vtbl_arylen_p
      MG_TYPE = PERL_MAGIC_arylen_p(@)
      MG_FLAGS = 0x02
        REFCOUNTED
    ARRAY = 0x183502c
    FILL = 99
    MAX = 123
    ARYLEN = 0x0
    FLAGS = (REAL)

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I wonder why the array comes with magic attached!

Update: Added Devel::Peek dump.

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Re^2: perl5.10 Devel::Size behaviour changed?
by ikegami (Patriarch) on Aug 25, 2009 at 14:10 UTC
    I couldn't leave it at that. It seems that Devel::Size actually modifies the array! 
    >perl -MDevel::Size=total_size -MDevel::Peek -e"my @a; total_size(\@a)
+ if $ARGV[0]; Dump \@a,1" 0
SV = RV(0x239ba8) at 0x239b9c
  REFCNT = 1
  FLAGS = (TEMP,ROK)
  RV = 0x1829954
  SV = PVAV(0x23aa60) at 0x1829954
    REFCNT = 2
    FLAGS = (PADMY)
    ARRAY = 0x0
    FILL = -1
    MAX = -1
    ARYLEN = 0x0
    FLAGS = (REAL)

>perl -MDevel::Size=total_size -MDevel::Peek -e"my @a; total_size(\@a)
+ if $ARGV[0]; Dump \@a,1" 1
SV = RV(0x239ba8) at 0x239b9c
  REFCNT = 1
  FLAGS = (TEMP,ROK)
  RV = 0x1829954
  SV = PVAV(0x23aa60) at 0x1829954
    REFCNT = 2
    FLAGS = (PADMY,RMG)
    MAGIC = 0x1824014
      MG_VIRTUAL = &PL_vtbl_arylen_p
      MG_TYPE = PERL_MAGIC_arylen_p(@)
      MG_FLAGS = 0x02
        REFCOUNTED
    ARRAY = 0x0
    FILL = -1
    MAX = -1
    ARYLEN = 0x0
    FLAGS = (REAL)

    [download]

    It's similar but different than using $#a: 

    >perl -MDevel::Size=total_size -MDevel::Peek -e"my @a; $#a if $ARGV[0]
+; Dump \@a,1" 0
SV = RV(0x239260) at 0x239254
  REFCNT = 1
  FLAGS = (TEMP,ROK)
  RV = 0x182991c
  SV = PVAV(0x23a168) at 0x182991c
    REFCNT = 2
    FLAGS = (PADMY)
    ARRAY = 0x0
    FILL = -1
    MAX = -1
    ARYLEN = 0x0
    FLAGS = (REAL)

>perl -MDevel::Size=total_size -MDevel::Peek -e"my @a; $#a if $ARGV[0]
+; Dump \@a,1" 1
SV = RV(0x239340) at 0x239334
  REFCNT = 1
  FLAGS = (TEMP,ROK)
  RV = 0x182991c
  SV = PVAV(0x23a168) at 0x182991c
    REFCNT = 2
    FLAGS = (PADMY,RMG)
    MAGIC = 0x1823de4
      MG_VIRTUAL = &PL_vtbl_arylen_p
      MG_TYPE = PERL_MAGIC_arylen_p(@)
      MG_FLAGS = 0x02
        REFCOUNTED
      MG_OBJ = 0x239254
      SV = PVMG(0x18fb364) at 0x239254
        REFCNT = 1
        FLAGS = (GMG,SMG)
        IV = 0
        NV = 0
        PV = 0
        MAGIC = 0x1823f0c
          MG_VIRTUAL = &PL_vtbl_arylen
          MG_TYPE = PERL_MAGIC_arylen(#)
          MG_OBJ = 0x182991c
    ARRAY = 0x0
    FILL = -1
    MAX = -1
    ARYLEN = 0x239254
    FLAGS = (REAL)

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        If it's a bug, it's not attributable to Devel::Size. Any operation that queries the size does the same thing: 

        perl -MDevel::Peek -e "my @a; Dump \@a, 1; printf qq[SIZE :%d\n], $#a;
+ Dump \@a, 1"
SV = RV(0x34e158) at 0x34e148
  REFCNT = 1
  FLAGS = (TEMP,ROK)
  RV = 0x276630
  SV = PVAV(0x34efb8) at 0x276630
    REFCNT = 2
    FLAGS = (PADMY)
    ARRAY = 0x0
    FILL = -1
    MAX = -1
    ARYLEN = 0x0
    FLAGS = (REAL)
SIZE :-1
SV = RV(0x34e290) at 0x34e280
  REFCNT = 1
  FLAGS = (TEMP,ROK)
  RV = 0x276630
  SV = PVAV(0x34efb8) at 0x276630
    REFCNT = 2
    FLAGS = (PADMY,RMG)
    MAGIC = 0x27fde8
      MG_VIRTUAL = &PL_vtbl_arylen_p
      MG_TYPE = PERL_MAGIC_arylen_p(@)
      MG_FLAGS = 0x02
        REFCOUNTED
      MG_OBJ = 0x34e148
      SV = PVMG(0x261f18) at 0x34e148
        REFCNT = 1
        FLAGS = (GMG,SMG,pIOK)
        IV = -1
        NV = 0
        PV = 0
        MAGIC = 0x27fcf8
          MG_VIRTUAL = &PL_vtbl_arylen
          MG_TYPE = PERL_MAGIC_arylen(#)
          MG_OBJ = 0x276630
    ARRAY = 0x0
    FILL = -1
    MAX = -1
    ARYLEN = 0x34e148
    FLAGS = (REAL)

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        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.
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