Inconsistency between NULL CPointer behavior jvm vs moar

[p6rt]

Migrated from rt.perl.org#124214 (status was 'resolved')

Searchable as RT124214$

[p6rt]

From @skids

Pointer-based classes are behaving differently on moar and jvm​:

(03/30/2015 10​:49​:07 PM) skids​: r​: use NativeCall; sub strstr(Str $n, Str $c) returns OpaquePointer is native { } ; my $d = strstr("c","aaa"); $d.say; $d.defined.say;
(10​:49​:08 PM) camelia​: rakudo-moar 01e174​: OUTPUT«(Pointer)␤False␤»
(10​:49​:16 PM) skids​: j​: use NativeCall; sub strstr(Str $n, Str $c) returns OpaquePointer is native { } ; my $d = strstr("c","aaa"); $d.say; $d.defined.say;
(10​:49​:24 PM) camelia​: rakudo-jvm 01e174​: OUTPUT«Pointer<NULL>␤True␤»
(11​:04​:32 PM) skids​: j​: use NativeCall; class f is repr('CPointer') { }; sub strstr(Str $n, Str $c) returns f is native { } ; my $d = strstr("c","aaa"); $d.say; $d.defined.say;
(11​:04​:37 PM) camelia​: rakudo-jvm 6186f0​: OUTPUT«f.new␤True␤»
(11​:05​:29 PM) skids​: m​: use NativeCall; class f is repr('CPointer') { }; sub strstr(Str $n, Str $c) returns f is native { } ; my $d = strstr("c","aaa"); $d.say; $d.defined.say;
(11​:05​:30 PM) camelia​: rakudo-moar 6186f0​: OUTPUT«(f)␤False␤»

This has broken previously-working assumptions about CPointer-based classes on JVM.

Since CPointer type objects passed to native functions cause a NULL pointer
to be passed, it would be consistent for the reverse to work as well,
and that would be consistent with the C/Perl failure case return value idioms.

If there is also a use case for a pointer class that is .defined when NULL, there
should be a way to distinguish between them and the idiomatic behavior.

This patch gets you halfway to tests, once the correct behavior is decided.
(Also fixes a minor typo)

Inline Patch

diff --git a/t/04-nativecall/04-pointers.c b/t/04-nativecall/04-pointers.c
index 0b617c6..230515a 100644
--- a/t/04-nativecall/04-pointers.c
+++ b/t/04-nativecall/04-pointers.c
@@ -18,3 +18,13 @@ DLLEXPORT int CompareSomePointer(void *ptr)
     int x = strcmp("Got passed back the pointer I returned", ptr) == 0;
     return x;
 }
+
+DLLEXPORT void * ReturnNullPointer()
+{
+    return NULL;
+}
+
+DLLEXPORT void * ReturnNullOpaquePointer()
+{
+    return NULL;
+}
diff --git a/t/04-nativecall/04-pointers.t b/t/04-nativecall/04-pointers.t
index 0bdad20..1b1b59c 100644
--- a/t/04-nativecall/04-pointers.t
+++ b/t/04-nativecall/04-pointers.t
@@ -10,6 +10,9 @@ compile_test_lib('04-pointers');
 
 sub ReturnSomePointer()         returns Pointer is native("./04-pointers") { * }
 sub CompareSomePointer(Pointer) returns int32   is native("./04-pointers") { * }
+sub ReturnNullPointer() returns Pointer   is native("./04-pointers") { * }
+sub ReturnNullOpaquePointer() returns OpaquePointer is native("./04-pointers") { * }
+
 
 my $x     = ReturnSomePointer();
 my int $a = 4321;
@@ -23,4 +26,9 @@ is Pointer.new.gist,       'Pointer<NULL>',   'Pointer.new gistifies to "Pointer
 is Pointer.new(0).gist,    'Pointer<NULL>',   'Pointer.new(0) gistifies to "Pointer<NULL>"';
 is Pointer.new(1234).gist, 'Pointer<0x4d2>',  'Pointer.new(1234) gistifies to "Pointer<0x4d2>"';
 is Pointer.new($a).gist,   'Pointer<0x10e1>', 'Pointer.new accepts a native int too';
-is Pointer.gist,           '(Pointer)',       'The Pointer type object gistifies ot "Pointer"';
+is Pointer.gist,           '(Pointer)',       'The Pointer type object gistifies to "Pointer"';
+
+ReturnNullPointer.say;
+ReturnNullOpaquePointer.say;
+ReturnNullPointer.defined.say;
+ReturnNullOpaquePointer.defined.say;

[p6rt]

From @FROGGS

The jvm got aligned to moar in​: Raku/nqp@0ccec451ed

[p6rt]

@FROGGS - Status changed from 'new' to 'resolved'

[p6rt]

From @FROGGS

Tests​: rakudo/rakudo@76ba0a26e3