Perl ABC- Perl ›
- Language implementation ›
- here
embedvar.h
embedvar.h is a header for abstracting interpreter variable and global variable.
Interpreter variable abstraction
The logic of the interpretation variable abstraction is as follows.
# if defined(MULTIPLICITY) / * cases 2 and 3 above */ # if defined(PERL_IMPLICIT_CONTEXT) # define vTHX aTHX # else # define vTHX PERL_GET_INTERP # endif # define PL_AboveLatin1 (vTHX->IAboveLatin1) # define PL_Argv (vTHX->IArgv) # define PL_Cmd (vTHX->ICmd) # define PL_DBcontrol (vTHX->IDBcontrol) # endif
First, when "MULTIPLICITY" is defined, it means that multiple interpreters can be used. In such cases, you need to access the variable for each interpreter.
Next, "PERL_IMPLICIT_CONTEXT" means that the interpreter is passed as the first argument of a function that starts with "Perl_", in the sense that an implicit context assumes it.
In general, if "MULTIPLICITY" is defined, consider that "PERL_IMPLICIT_CONTEXT" is defined.
"ATHX" is defined as follows:
/*perl.h */ # ifdef PERL_IMPLICIT_CONTEXT # define aTHX my_perl # end
my_perl is a global variable and represents an interpreter.
/* perlmain.c */static PerlInterpreter * my_perl;
Next, if "PERL_IMPLICIT_CONTEXT" is not defined, "PERL_GET_INTERP" is defined as follows and is the current interpreter. This is a global variable.
/*perl.h */ # define PERL_GET_INTERP (PL_curinterp)
/* perlvar.h */PERLVARI (G, curinterp, PerlInterpreter *, NULL) / * currently running interpreter * (initial parent interpreter under under * useithreads) */</pre> If "PERL_IMPLICT_CONTEXT" is defined, "vTHX" will be expanded as "my_perl", otherwise it will be expanded as "Gcurinterp". .. And the access to the interpreted variable is defined as follows. <pre> # define PL_AboveLatin1 (vTHX->IAboveLatin1)
Global variable abstraction
Next is the code for the abstraction of global variable. If "PERL_GLOBAL_STRUCT" is defined, the entire global variable exists as a single structure, otherwise it exists as a regular global variable. In both of these cases, you can access the variable with "PL_appctx".
# if defined(PERL_GLOBAL_STRUCT) # define PL_appctx (my_vars->Gappctx) # define PL_Gappctx (my_vars->Gappctx) # endif
/* perlmain.c */struct perl_vars * my_vars = init_global_struct ();