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Hiya Monks,

I'm trying to grok the infamous 'B' Module.
http://search.cpan.org/perldoc?B

This documentation assumes that the reader knows a fair amount about perl's internals including such things as SVs, OPs and the internal symbol table and syntax tree of a program.

I've read through the most obvious places... http://perldoc.perl.org/DB.html
http://perldoc.perl.org/perldebug.html
http://perldoc.perl.org/perldebguts.html
/usr/libdata/perl5/i386-openbsd/5.10.1/CORE/perl.h
/usr/libdata/perl5/i386-openbsd/5.10.1/CORE/handy.h

I'd like to find info on the naming convention and/or name definitions. Basically, what do the names mean and why are they named that way?

NAME    KNOWN           WILD GUESSES
SV      is a scalar     (WTF does the 'V' stand for?)
RV      is a Reference  (well, it was until Perl 5.11.*)
PV      is a string     (WTF does 'P' stand for?)
IV      is an integer
NV      is a number
LV      is ?            ("LeftValue?" LVALUE? Local? )
GV      is ?            (General? Global?, Garbage-Collected?)
AV      is ?            (Array?)
HV      is ?            (Hash?)
CV      is ?
FM      is ?
IO      is ?

PVIV    string and integer slots
PVNV    string and number slots
PVLV    is ?            (string of left value, e.g. func name)

OP                      (Operation?)
COP
LOOP                    (Loop Operation?)
PMOP
PVOP                    (String Operation?)
SVOP                    (Scalar Operation?)
UNOP
BINOP
LOGOP                   (Logic Operation? e.g. 'and' 'or')
PADOP
LISTOP

Much to the surprise of my local prune vendor, 'BM' is Boyer-Moore, a string search algorithm, but as far as I know, it's a no longer a used type/name. Digging around for the obvious is helpful... but it's like trying to learn by osmosis.

$ perl -e 'print(ref(\pos) . "\n");'
LVALUE

$ perl -e 'use B; print(ref(B::svref_2object(\substr "foo",1)) . "\n")
+;'
B::PVLV

$ perl -MO=Terse -ce '$v=2; $v=2.3; $v="txt"; print index($v,"x",0);'
LISTOP (0x7d61afc0) leave [1]
    OP (0x7df6e560) enter
    COP (0x8b34b340) nextstate
    BINOP (0x7d61aa60) sassign
        SVOP (0x7d61a9c0) const  IV (0x85306280) 2
        UNOP (0x7d61af20) null [15]
            SVOP (0x7d61afe0) gvsv  GV (0x86712440) *v
    COP (0x8b34b380) nextstate
    BINOP (0x7d61afa0) sassign
        SVOP (0x7cd4e6c0) const  NV (0x86712460) 2.3
        UNOP (0x7d61af60) null [15]
            SVOP (0x7d61ae60) gvsv  GV (0x86712440) *v
    COP (0x7f6ffe40) nextstate
    BINOP (0x7df6edc0) sassign
        SVOP (0x7df6ee60) const  PV (0x86712510) "txt"
        UNOP (0x7df6ed00) null [15]
            SVOP (0x7df6eca0) gvsv  GV (0x86712440) *v
    COP (0x7f6fff80) nextstate
    LISTOP (0x7df6ef60) print
        OP (0x7df6ef20) pushmark
        LISTOP (0x7d61ac80) index [1]
            OP (0x7df6ed60) null [3]
            UNOP (0x7df6eee0) null [15]
                SVOP (0x7df6eda0) gvsv  GV (0x86712440) *v
            SVOP (0x7d61ad00) const  GV (0x867124b0) "x"
            SVOP (0x7df6eec0) const  IV (0x86712470) 0
-e syntax OK

$ perl -MO=Terse -ce '@a = qw(1 two 3);foreach (@a) {print "$_\n";}'
LISTOP (0x8b2d0ec0) leave [1]
    OP (0x81b42e00) enter
    COP (0x8945b100) nextstate
    BINOP (0x818e7080) aassign [2]
        UNOP (0x83c67f60) null [142]
            OP (0x83c67fe0) pushmark
            SVOP (0x83c67f80) const  PV (0x888cf470) "1"
            SVOP (0x83c67ca0) const  PV (0x888cf510) "two"
            SVOP (0x83c67fa0) const  PV (0x888cf4b0) "3"
        UNOP (0x83c67ce0) null [142]
            OP (0x8a367fa0) pushmark
            UNOP (0x83c67f40) rv2av [1]
                SVOP (0x7e65a4c0) gv  GV (0x888cf440) *a
    COP (0x88486f80) nextstate
    BINOP (0x87348f00) leaveloop
        LOOP (0x88486ec0) enteriter
            OP (0x87348f80) null [3]
            UNOP (0x873489a0) null [142]
                OP (0x87348ee0) pushmark
                UNOP (0x87348a20) rv2av [3]
                    SVOP (0x87348680) gv  GV (0x888cf440) *a
            SVOP (0x87348fc0) gv  GV (0x7f67f170) *_
        UNOP (0x87348d80) null
            LOGOP (0x87348f60) and
                OP (0x87348fa0) iter
                LISTOP (0x87348e40) lineseq
                    COP (0x8945b140) nextstate
                    LISTOP (0x87348c20) print
                        OP (0x87348d20) pushmark
                        UNOP (0x87348f40) null [67]
                            OP (0x87348e20) null [3]
                            BINOP (0x83c67c60) concat [4]
                                UNOP (0x83c679c0) null [15]
                                    SVOP (0x83c67f00) gvsv  GV (0x7f67
+f170) *_
                                SVOP (0x87348da0) const  PV (0x888cf49
+0) "\n"
                    OP (0x87348e80) unstack
-e syntax OK
[download]

If you know were the names are documented, or know that they are undocumented, please kick the knowledge downstairs to the unwashed. Thanks!

In reply to Where to find info on low level perl internals names? by Anonymous Monk

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