py: Extend native type-sig to use 4 bits, so uint is separate to ptr.

Before this patch, the native types for uint and ptr/ptr8/ptr16/ptr32
all overlapped and it was possible to make a mistake in casting.  Now,
these types are all separate and any coding mistakes will be raised
as runtime errors.

py/emitnative.c

@@ -510,19 +510,19 @@ typedef enum {
     STACK_IMM,
 } stack_info_kind_t;
 
-// these enums must be distinct and the bottom 2 bits
+// these enums must be distinct and the bottom 4 bits
 // must correspond to the correct MP_NATIVE_TYPE_xxx value
 typedef enum {
     VTYPE_PYOBJ = 0x00 | MP_NATIVE_TYPE_OBJ,
     VTYPE_BOOL = 0x00 | MP_NATIVE_TYPE_BOOL,
     VTYPE_INT = 0x00 | MP_NATIVE_TYPE_INT,
     VTYPE_UINT = 0x00 | MP_NATIVE_TYPE_UINT,
+    VTYPE_PTR = 0x00 | MP_NATIVE_TYPE_PTR,
+    VTYPE_PTR8 = 0x00 | MP_NATIVE_TYPE_PTR8,
+    VTYPE_PTR16 = 0x00 | MP_NATIVE_TYPE_PTR16,
+    VTYPE_PTR32 = 0x00 | MP_NATIVE_TYPE_PTR32,
 
-    VTYPE_PTR = 0x10 | MP_NATIVE_TYPE_UINT, // pointer to word sized entity
-    VTYPE_PTR8 = 0x20 | MP_NATIVE_TYPE_UINT,
-    VTYPE_PTR16 = 0x30 | MP_NATIVE_TYPE_UINT,
-    VTYPE_PTR32 = 0x40 | MP_NATIVE_TYPE_UINT,
-    VTYPE_PTR_NONE = 0x50 | MP_NATIVE_TYPE_UINT,
+    VTYPE_PTR_NONE = 0x50 | MP_NATIVE_TYPE_PTR,
 
     VTYPE_UNBOUND = 0x60 | MP_NATIVE_TYPE_OBJ,
     VTYPE_BUILTIN_CAST = 0x70 | MP_NATIVE_TYPE_OBJ,
@@ -882,10 +882,10 @@ STATIC void emit_native_end_pass(emit_t *emit) {
         mp_uint_t f_len = ASM_GET_CODE_SIZE(emit->as);
 
         // compute type signature
-        // note that the lower 2 bits of a vtype are tho correct MP_NATIVE_TYPE_xxx
-        mp_uint_t type_sig = emit->return_vtype & 3;
+        // note that the lower 4 bits of a vtype are tho correct MP_NATIVE_TYPE_xxx
+        mp_uint_t type_sig = emit->return_vtype & 0xf;
         for (mp_uint_t i = 0; i < emit->scope->num_pos_args; i++) {
-            type_sig |= (emit->local_vtype[i] & 3) << (i * 2 + 2);
+            type_sig |= (emit->local_vtype[i] & 0xf) << (i * 4 + 4);
         }
 
         mp_emit_glue_assign_native(emit->scope->raw_code,
@@ -2382,7 +2382,7 @@ STATIC void emit_native_call_function(emit_t *emit, mp_uint_t n_positional, mp_u
                 vtype_kind_t vtype;
                 emit_pre_pop_reg(emit, &vtype, REG_ARG_1);
                 emit_pre_pop_discard(emit);
-                emit_call_with_imm_arg(emit, MP_F_CONVERT_OBJ_TO_NATIVE, MP_NATIVE_TYPE_UINT, REG_ARG_2); // arg2 = type
+                emit_call_with_imm_arg(emit, MP_F_CONVERT_OBJ_TO_NATIVE, vtype_cast, REG_ARG_2); // arg2 = type
                 emit_post_push_reg(emit, vtype_cast, REG_RET);
                 break;
             }

py/nativeglue.c

@@ -45,20 +45,17 @@
 // convert a Micro Python object to a valid native value based on type
 mp_uint_t mp_convert_obj_to_native(mp_obj_t obj, mp_uint_t type) {
     DEBUG_printf("mp_convert_obj_to_native(%p, " UINT_FMT ")\n", obj, type);
-    switch (type & 3) {
+    switch (type & 0xf) {
         case MP_NATIVE_TYPE_OBJ: return (mp_uint_t)obj;
         case MP_NATIVE_TYPE_BOOL:
-        case MP_NATIVE_TYPE_INT: return mp_obj_get_int_truncated(obj);
-        case MP_NATIVE_TYPE_UINT: {
+        case MP_NATIVE_TYPE_INT:
+        case MP_NATIVE_TYPE_UINT: return mp_obj_get_int_truncated(obj);
+        default: { // a pointer
             mp_buffer_info_t bufinfo;
-            if (mp_get_buffer(obj, &bufinfo, MP_BUFFER_RW)) {
+            mp_get_buffer_raise(obj, &bufinfo, MP_BUFFER_RW);
             return (mp_uint_t)bufinfo.buf;
-            } else {
-                return mp_obj_get_int_truncated(obj);
         }
     }
-        default: assert(0); return 0;
-    }
 }
 
 #endif
@@ -68,12 +65,14 @@ mp_uint_t mp_convert_obj_to_native(mp_obj_t obj, mp_uint_t type) {
 // convert a native value to a Micro Python object based on type
 mp_obj_t mp_convert_native_to_obj(mp_uint_t val, mp_uint_t type) {
     DEBUG_printf("mp_convert_native_to_obj(" UINT_FMT ", " UINT_FMT ")\n", val, type);
-    switch (type & 3) {
+    switch (type & 0xf) {
         case MP_NATIVE_TYPE_OBJ: return (mp_obj_t)val;
         case MP_NATIVE_TYPE_BOOL: return mp_obj_new_bool(val);
         case MP_NATIVE_TYPE_INT: return mp_obj_new_int(val);
         case MP_NATIVE_TYPE_UINT: return mp_obj_new_int_from_uint(val);
-        default: assert(0); return mp_const_none;
+        default: // a pointer
+            // we return just the value of the pointer as an integer
+            return mp_obj_new_int_from_uint(val);
     }
 }
 

py/objfun.c

@@ -404,17 +404,17 @@ STATIC mp_obj_t fun_viper_call(mp_obj_t self_in, size_t n_args, size_t n_kw, con
     if (n_args == 0) {
         ret = ((viper_fun_0_t)fun)();
     } else if (n_args == 1) {
-        ret = ((viper_fun_1_t)fun)(mp_convert_obj_to_native(args[0], self->type_sig >> 2));
+        ret = ((viper_fun_1_t)fun)(mp_convert_obj_to_native(args[0], self->type_sig >> 4));
     } else if (n_args == 2) {
-        ret = ((viper_fun_2_t)fun)(mp_convert_obj_to_native(args[0], self->type_sig >> 2), mp_convert_obj_to_native(args[1], self->type_sig >> 4));
+        ret = ((viper_fun_2_t)fun)(mp_convert_obj_to_native(args[0], self->type_sig >> 4), mp_convert_obj_to_native(args[1], self->type_sig >> 8));
     } else if (n_args == 3) {
-        ret = ((viper_fun_3_t)fun)(mp_convert_obj_to_native(args[0], self->type_sig >> 2), mp_convert_obj_to_native(args[1], self->type_sig >> 4), mp_convert_obj_to_native(args[2], self->type_sig >> 6));
+        ret = ((viper_fun_3_t)fun)(mp_convert_obj_to_native(args[0], self->type_sig >> 4), mp_convert_obj_to_native(args[1], self->type_sig >> 8), mp_convert_obj_to_native(args[2], self->type_sig >> 12));
     } else if (n_args == 4) {
         ret = ((viper_fun_4_t)fun)(
-            mp_convert_obj_to_native(args[0], self->type_sig >> 2),
-            mp_convert_obj_to_native(args[1], self->type_sig >> 4),
-            mp_convert_obj_to_native(args[2], self->type_sig >> 6),
-            mp_convert_obj_to_native(args[3], self->type_sig >> 8)
+            mp_convert_obj_to_native(args[0], self->type_sig >> 4),
+            mp_convert_obj_to_native(args[1], self->type_sig >> 8),
+            mp_convert_obj_to_native(args[2], self->type_sig >> 12),
+            mp_convert_obj_to_native(args[3], self->type_sig >> 16)
         );
     } else {
         // TODO 5 or more arguments not supported for viper call

py/runtime0.h

@@ -37,6 +37,10 @@
 #define MP_NATIVE_TYPE_BOOL (0x01)
 #define MP_NATIVE_TYPE_INT  (0x02)
 #define MP_NATIVE_TYPE_UINT (0x03)
+#define MP_NATIVE_TYPE_PTR  (0x04)
+#define MP_NATIVE_TYPE_PTR8 (0x05)
+#define MP_NATIVE_TYPE_PTR16 (0x06)
+#define MP_NATIVE_TYPE_PTR32 (0x07)
 
 typedef enum {
     MP_UNARY_OP_BOOL, // __bool__