Hunt the func

BrowserUk has asked for the wisdom of the Perl Monks concerning the following question:

Given these compile options:

  Compile-time options: MULTIPLICITY PERL_DONT_CREATE_GVSV
                        PERL_IMPLICIT_CONTEXT PERL_IMPLICIT_SYS
                        PERL_MALLOC_WRAP PL_OP_SLAB_ALLOC USE_64_BIT_I
+NT
                        USE_ITHREADS USE_LARGE_FILES USE_PERLIO
  Built under MSWin32
[download]

Can anyone tell me what function is being called here:

## perlio.c(592) v5.10.1
         return (*tab->Dup)(aTHX_ PerlIO_allocate(aTHX), f, param, fla
+gs);
[download]

And also, how did you track it down?

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Re: Hunt the func by ikegami (Patriarch) on Mar 16, 2010 at 23:29 UTC
`tab` is a pointer to a `PerlIO_funcs` struct, a method lookup table. (Search for `PERLIO_FUNCS_DECL`, the core ones being in `perlio.c`.) Each PerlIO layer has one. You can get the handle's layers using `PerlIO::get_layers($fh)`. `>perl -le"print for PerlIO::get_layers(STDIN)" unix crlf` [download]	[reply] [d/l] [select]