From 02cc288edbc47a3b21b88b83f15990cc5a36ed23 Mon Sep 17 00:00:00 2001
From: Damien George <damien.p.george@gmail.com>
Date: Fri, 8 Mar 2019 15:48:20 +1100
Subject: [PATCH] py: Add independent config for debugging sentinel object
 values.

The new compile-time option is MICROPY_DEBUG_MP_OBJ_SENTINELS, disabled by
default.  This is to allow finer control of whether this debugging feature
is enabled or not (because, for example, this setting must be the same for
mpy-cross and the MicroPython main code when using native code generation).
---
 py/emitnative.c |  8 ++++----
 py/mpconfig.h   |  5 +++++
 py/obj.h        | 10 +++++-----
 3 files changed, 14 insertions(+), 9 deletions(-)

diff --git a/py/emitnative.c b/py/emitnative.c
index c8a1a33d6..0c756f9a5 100644
--- a/py/emitnative.c
+++ b/py/emitnative.c
@@ -2094,12 +2094,12 @@ STATIC void emit_native_for_iter(emit_t *emit, mp_uint_t label) {
     emit_get_stack_pointer_to_reg_for_pop(emit, REG_ARG_1, MP_OBJ_ITER_BUF_NSLOTS);
     adjust_stack(emit, MP_OBJ_ITER_BUF_NSLOTS);
     emit_call(emit, MP_F_NATIVE_ITERNEXT);
-    #ifdef NDEBUG
-    MP_STATIC_ASSERT(MP_OBJ_STOP_ITERATION == 0);
-    ASM_JUMP_IF_REG_ZERO(emit->as, REG_RET, label, false);
-    #else
+    #if MICROPY_DEBUG_MP_OBJ_SENTINELS
     ASM_MOV_REG_IMM(emit->as, REG_TEMP1, (mp_uint_t)MP_OBJ_STOP_ITERATION);
     ASM_JUMP_IF_REG_EQ(emit->as, REG_RET, REG_TEMP1, label);
+    #else
+    MP_STATIC_ASSERT(MP_OBJ_STOP_ITERATION == 0);
+    ASM_JUMP_IF_REG_ZERO(emit->as, REG_RET, label, false);
     #endif
     emit_post_push_reg(emit, VTYPE_PYOBJ, REG_RET);
 }
diff --git a/py/mpconfig.h b/py/mpconfig.h
index c4b62dd84..893ac7dc7 100644
--- a/py/mpconfig.h
+++ b/py/mpconfig.h
@@ -414,6 +414,11 @@
 #define MICROPY_DEBUG_VERBOSE (0)
 #endif
 
+// Whether to enable debugging versions of MP_OBJ_NULL/STOP_ITERATION/SENTINEL
+#ifndef MICROPY_DEBUG_MP_OBJ_SENTINELS
+#define MICROPY_DEBUG_MP_OBJ_SENTINELS (0)
+#endif
+
 // Whether to enable a simple VM stack overflow check
 #ifndef MICROPY_DEBUG_VM_STACK_OVERFLOW
 #define MICROPY_DEBUG_VM_STACK_OVERFLOW (0)
diff --git a/py/obj.h b/py/obj.h
index e8575dbd1..4d42c43de 100644
--- a/py/obj.h
+++ b/py/obj.h
@@ -65,14 +65,14 @@ typedef struct _mp_obj_base_t mp_obj_base_t;
 // For debugging purposes they are all different.  For non-debug mode, we alias
 // as many as we can to MP_OBJ_NULL because it's cheaper to load/compare 0.
 
-#ifdef NDEBUG
-#define MP_OBJ_NULL             (MP_OBJ_FROM_PTR((void*)0))
-#define MP_OBJ_STOP_ITERATION   (MP_OBJ_FROM_PTR((void*)0))
-#define MP_OBJ_SENTINEL         (MP_OBJ_FROM_PTR((void*)4))
-#else
+#if MICROPY_DEBUG_MP_OBJ_SENTINELS
 #define MP_OBJ_NULL             (MP_OBJ_FROM_PTR((void*)0))
 #define MP_OBJ_STOP_ITERATION   (MP_OBJ_FROM_PTR((void*)4))
 #define MP_OBJ_SENTINEL         (MP_OBJ_FROM_PTR((void*)8))
+#else
+#define MP_OBJ_NULL             (MP_OBJ_FROM_PTR((void*)0))
+#define MP_OBJ_STOP_ITERATION   (MP_OBJ_FROM_PTR((void*)0))
+#define MP_OBJ_SENTINEL         (MP_OBJ_FROM_PTR((void*)4))
 #endif
 
 // These macros/inline functions operate on objects and depend on the