fix type of Perl_magic_getarylen

This function is used as part of PL_magic_vtables, so its type must be
'int (pTHX_ SV *, MAGIC *)' exactly (no const). With the right type, we
no longer need an ad-hoc cast in mg_vtables.h, which means we no longer
need the 'const' code in regen/mg_vtable.pl, which was a special case
used by this one function only.

Should fix ASan complaints about functions being called with incorrect
types.

Author: mauke

embed.fnc

@@ -1909,7 +1909,7 @@ p	|int	|magic_freeutf8 |NN SV *sv				\
 p	|int	|magic_get	|NN SV *sv				\
 				|NN MAGIC *mg
 p	|int	|magic_getarylen|NN SV *sv				\
-				|NN const MAGIC *mg
+				|NN MAGIC *mg
 p	|int	|magic_getdebugvar					\
 				|NN SV *sv				\
 				|NN MAGIC *mg

mg.c

@@ -2364,7 +2364,7 @@ Perl_magic_setdbline(pTHX_ SV *sv, MAGIC *mg)
 }
 
 int
-Perl_magic_getarylen(pTHX_ SV *sv, const MAGIC *mg)
+Perl_magic_getarylen(pTHX_ SV *sv, MAGIC *mg)
 {
     AV * const obj = MUTABLE_AV(mg->mg_obj);
 

mg_vtable.h

@@ -245,11 +245,6 @@ BEGIN
 #       prefix the vtable with the specified entry (e.g. '#ifdef FOO')
 #       and suffix it with '#else { 0, 0, 0, 0, 0, 0, 0, 0 } #endif'
 #
-#    const
-#       special-case cast a 'get' function whose signature expects
-#       a pointer to constant magic, so that it can be added to a vtable
-#       which expects pointers to functions without the 'const'.
-#
 #    get
 #    set
 #    len
@@ -277,7 +272,7 @@ BEGIN
      'dbline' => {set => 'setdbline'},
      'isa' => {set => 'setisa', clear => 'clearisa'},
      'isaelem' => {set => 'setisa'},
-     'arylen' => {get => 'getarylen', set => 'setarylen', const => 1},
+     'arylen' => {get => 'getarylen', set => 'setarylen'},
      'arylen_p' => {clear => 'cleararylen_p', free => 'freearylen_p'},
      'mglob'    => {set   => 'setmglob',
                     free  => 'freemglob' },
@@ -528,7 +523,6 @@ BEGIN
         $data->{$_} ? "Perl_magic_$data->{$_}" : 0;
     } qw(get set len clear free copy dup local);
 
-    $funcs[0] = "(int (*)(pTHX_ SV *, MAGIC *))" . $funcs[0] if $data->{const};
     my $funcs = join ", ", @funcs;
 
     # Because we can't have a , after the last {...}