ParseXS: always XSprePUSH when producing an output list

The late XSprePUSH with a non-PUSHx() RETVAL was causing the
stack and accesses to ST(n) to be out of sync.

If generated RETVAL code does write directly to ST(n) (as much does),
doesn't generate a push and we're generating output list code,
adjust SP to match to keep things in sync.

Also test that the original example case that worked, continues to
work.

Fixes #19054

dist/ExtUtils-ParseXS/lib/ExtUtils/ParseXS.pm

@@ -690,10 +690,17 @@ EOF
         do_push     => undef,
       } ) for grep $self->{in_out}->{$_} =~ /OUT$/, sort keys %{ $self->{in_out} };
 
-      my $prepush_done;
+      my $c = @{ $outlist_ref };
+      if ($c) {
+        my $ext = $c;
+        ++$ext if $self->{gotRETVAL} || $wantRETVAL;
+        print "\tXSprePUSH;";
+        print "\tEXTEND(SP,$ext);\n";
+      }
       # all OUTPUT done, so now push the return value on the stack
       if ($self->{gotRETVAL} && $self->{RETVAL_code}) {
         print "\t$self->{RETVAL_code}\n";
+        print "\t++SP;\n" if $c;
       }
       elsif ($self->{gotRETVAL} || $wantRETVAL) {
         my $outputmap = $self->{typemap}->get_outputmap( ctype => $self->{ret_type} );
@@ -708,8 +715,9 @@ EOF
           );
           if (not $trgt->{with_size} and $trgt->{type} eq 'p') { # sv_setpv
             # PUSHp corresponds to sv_setpvn.  Treat sv_setpv directly
-            print "\tsv_setpv(TARG, $what); XSprePUSH; PUSHTARG;\n";
-            $prepush_done = 1;
+              print "\tsv_setpv(TARG, $what);\n";
+              print "\tXSprePUSH;\n" unless $c;
+              print "\tPUSHTARG;\n";
           }
           else {
             my $tsize = $trgt->{what_size};
@@ -718,8 +726,8 @@ EOF
               qq("$tsize"),
               {var => $var, type => $self->{ret_type}}
             );
-            print "\tXSprePUSH; PUSH$trgt->{type}($what$tsize);\n";
-            $prepush_done = 1;
+            print "\tXSprePUSH;\n" unless $c;
+            print "\tPUSH$trgt->{type}($what$tsize);\n";
           }
         }
         else {
@@ -731,14 +739,12 @@ EOF
             do_setmagic => 0,
             do_push     => undef,
           } );
+          print "\t++SP;\n" if $c;
         }
       }
 
       $xsreturn = 1 if $self->{ret_type} ne "void";
       my $num = $xsreturn;
-      my $c = @{ $outlist_ref };
-      print "\tXSprePUSH;" if $c and not $prepush_done;
-      print "\tEXTEND(SP,$c);\n" if $c;
       $xsreturn += $c;
       $self->generate_output( {
         type        => $self->{var_types}->{$_},

dist/ExtUtils-ParseXS/t/002-more.t

@@ -9,7 +9,7 @@ use ExtUtils::CBuilder;
 use attributes;
 use overload;
 
-plan tests => 30;
+plan tests => 32;
 
 my ($source_file, $obj_file, $lib_file);
 
@@ -91,6 +91,12 @@ SKIP: {
 
   is_deeply [XSMore::outlist()], [ord('a'), ord('b')], 'the OUTLIST keyword';
 
+  is_deeply [XSMore::outlist_bool("a", "b")], [ !0, "ab" ],
+             "OUTLIST with a bool RETVAL";
+
+  is_deeply [XSMore::outlist_int("c", "d")], [ 11, "cd" ],
+             "OUTLIST with an int RETVAL";
+
   # eval so compile-time sees any prototype
   is_deeply [ eval 'XSMore::outlist()' ], [ord('a'), ord('b')], 'OUTLIST prototypes';
 

dist/ExtUtils-ParseXS/t/XSMore.xs

@@ -38,6 +38,36 @@ outlist(int* a, int* b){
 	*b = 'b';
 }
 
+STATIC bool
+outlist_bool(const char *a, const char *b, char **c)
+{
+   dTHX;
+   STRLEN lena = strlen(a);
+   STRLEN lenb = strlen(b);
+   STRLEN lenc = lena + lenb;
+   Newx(*c, lenc+1, char);
+   strcpy(*c, a);
+   strcat(*c, b);
+   SAVEFREEPV(*c);
+
+   return TRUE;
+}
+
+STATIC int
+outlist_int(const char *a, const char *b, char **c)
+{
+   dTHX;
+   STRLEN lena = strlen(a);
+   STRLEN lenb = strlen(b);
+   STRLEN lenc = lena + lenb;
+   Newx(*c, lenc+1, char);
+   strcpy(*c, a);
+   strcat(*c, b);
+   SAVEFREEPV(*c);
+
+   return 11;
+}
+
 STATIC int
 len(const char* const s, int const l){
 	PERL_UNUSED_ARG(s);
@@ -201,6 +231,12 @@ CLEANUP:
 void
 outlist(OUTLIST int a, OUTLIST int b)
 
+bool
+outlist_bool(const char *a, const char *b, OUTLIST char *c)
+
+int
+outlist_int(const char *a, const char *b, OUTLIST char *c)
+
 int
 len(char* s, int length(s))