64-bit stack: call_sv mark and return value handling

call_sv() used I32 for a saved mark and the return value.

The XS::APItest call_sv() wrapper used an I32 index to reposition
the argument list supplied to call_sv().

I haven't created additional tests for call_argv(), call_pv() nor
call_method(), these simply pass the return value on, I don't think
it worth the extra tests.

embed.fnc

@@ -752,7 +752,7 @@ CTdpx	|U8 *	|bytes_from_utf8_loc					\
 				|NULLOK const U8 **first_unconverted
 Adpx	|U8 *	|bytes_to_utf8	|NN const U8 *s 			\
 				|NN STRLEN *lenp
-AOdp	|I32	|call_argv	|NN const char *sub_name		\
+AOdp	|SSize_t|call_argv	|NN const char *sub_name		\
 				|I32 flags				\
 				|NN char **argv
 
@@ -765,13 +765,13 @@ Adp	|const PERL_CONTEXT *|caller_cx 				\
 				|NULLOK const PERL_CONTEXT **dbcxp
 Cp	|void	|call_list	|I32 oldscope				\
 				|NN AV *paramList
-AOdp	|I32	|call_method	|NN const char *methname		\
+AOdp	|SSize_t|call_method	|NN const char *methname		\
 				|I32 flags
 CTadop	|Malloc_t|calloc	|MEM_SIZE elements			\
 				|MEM_SIZE size
-AOdp	|I32	|call_pv	|NN const char *sub_name		\
+AOdp	|SSize_t|call_pv	|NN const char *sub_name		\
 				|I32 flags
-AOdp	|I32	|call_sv	|NN SV *sv				\
+AOdp	|SSize_t|call_sv	|NN SV *sv				\
 				|volatile I32 flags
 : Used in several source files
 Rp	|bool	|cando		|Mode_t mode				\

ext/XS-APItest/APItest.xs

@@ -2760,7 +2760,7 @@ call_sv(sv, flags, ...)
     SV* sv
     I32 flags
     PREINIT:
-        I32 i;
+        SSize_t i;
     PPCODE:
         for (i=0; i<items-2; i++)
             ST(i) = ST(i+2); /* pop first two args */

perl.c

@@ -2971,7 +2971,7 @@ Approximate Perl equivalent: C<&{"$sub_name"}(@$argv)>.
 =cut
 */
 
-I32
+SSize_t
 Perl_call_argv(pTHX_ const char *sub_name, I32 flags, char **argv)
 
                         /* See G_* flags in cop.h */
@@ -3005,7 +3005,7 @@ Performs a callback to the specified Perl sub.  See L<perlcall>.
 =cut
 */
 
-I32
+SSize_t
 Perl_call_pv(pTHX_ const char *sub_name, I32 flags)
                         /* name of the subroutine */
                         /* See G_* flags in cop.h */
@@ -3024,7 +3024,7 @@ be on the stack.  See L<perlcall>.
 =cut
 */
 
-I32
+SSize_t
 Perl_call_method(pTHX_ const char *methname, I32 flags)
                         /* name of the subroutine */
                         /* See G_* flags in cop.h */
@@ -3068,14 +3068,14 @@ See L<perlcall>.
 =cut
 */
 
-I32
+SSize_t
 Perl_call_sv(pTHX_ SV *sv, volatile I32 flags)
                         /* See G_* flags in cop.h */
 {
     LOGOP myop;		/* fake syntax tree node */
     METHOP method_op;
-    I32 oldmark;
-    volatile I32 retval = 0;
+    SSize_t oldmark;
+    volatile SSize_t retval = 0;
     bool oldcatch = CATCH_GET;
     int ret;
     OP* const oldop = PL_op;

t/bigmem/stack.t

@@ -18,6 +18,8 @@ $Config{ptrsize} >= 8
 my @x;
 $x[0x8000_0000] = "Hello";
 
+my $arg_count;
+
 my @tests =
   (
       [ mark => sub
@@ -181,6 +183,20 @@ my @tests =
               }
           }
       ],
+      [
+          call_sv_args => sub {
+              undef $arg_count;
+              my $ret_count = XS::APItest::call_sv(\&arg_count, G_LIST, x());
+              is($ret_count, 0, "call_sv with 2G args - arg_count() returns nothing");
+              is($arg_count, scalar @x, "check call_sv argument handling - argument count");
+          },
+      ],
+      [
+          call_sv_mark => sub {
+              my $ret_count = ( x(), XS::APItest::call_sv(\&list, G_LIST) )[-1];
+              is($ret_count, 2, "call_sv with deep stack - returned value count");
+          },
+      ],
      );
 
 # these tests are slow, let someone debug them one at a time
@@ -228,6 +244,11 @@ sub list {
     return shift() ? (1, 2) : (2, 1);
 }
 
+sub arg_count {
+    $arg_count = @_;
+    ();
+}
+
 package ScalarTie;
 
 sub TIESCALAR {