added the ability to inspect the stack from the debugger

samples/func.noja

@@ -1,6 +1,6 @@
 
 fun k(k)
-	return k();
+	return k(k);
 
 k(k);
 

src/debug.c

@@ -267,7 +267,8 @@ _Bool Debug_Callback(Runtime *runtime, void *userp)
 						"step .............. Run an instruction\n"
 						"quit .............. Stop execution\n"
 						"continue .......... Run until a breakpoint or the end of the code is reached\n"
-						"breakpoint ........ Add a breakpoint\n");
+						"breakpoint ........ Add a breakpoint\n"
+						"stack ............. Show the contents of the stack\n");
 						}
 					else if(!strcmp(argv[1], "help"))
 						{
@@ -339,6 +340,17 @@ _Bool Debug_Callback(Runtime *runtime, void *userp)
 								"             | a line number, a character offset or an instruction index.\n"
 								"\n");
 						}
+					else if(!strcmp(argv[1], "stack"))
+						{
+							fprintf(stderr, 
+								"\n"
+								"     Command | stack\n"
+								"             | \n"
+								"       Usage | > stack\n"
+								"             | \n"
+								" Description | Show the contents of the stack.\n"
+								"\n");
+						}
 					else
 						{
 							fprintf(stdout, "Unknown command \"%s\".\n", argv[1]);
@@ -436,6 +448,35 @@ _Bool Debug_Callback(Runtime *runtime, void *userp)
 				{
 					return 1;
 				}
+			else if(!strcmp(argv[0], "stack"))
+				{
+					Stack *stack = Runtime_GetStack(runtime);
+					assert(stack != NULL);
+
+					Error error;
+					Error_Init(&error);
+
+					if(Stack_Size(stack) == 0)
+						fprintf(stderr, "The stack is empty.\n");
+
+					for(int i = 0; i < (int) Stack_Size(stack); i += 1)
+						{
+							Object *obj = Stack_Top(stack, -i);
+							assert(obj != NULL);
+
+							fprintf(stderr, "  %d | ", i);
+							Object_Print(obj, stderr, &error);
+
+							if(error.occurred)
+								{
+									Error_Free(&error);
+									Error_Init(&error);
+									fprintf(stderr, "(unprintable)");
+								}
+
+							fprintf(stderr, "\n");
+						}
+				}
 			else if(!strcmp(argv[0], "quit"))
 				{
 					return 0;

src/runtime/runtime.c

@@ -4,7 +4,7 @@
 #include "runtime.h"
 
 #define MAX_FRAME_STACK 16
-#define MAX_FRAMES 1024
+#define MAX_FRAMES 16
 
 typedef struct Frame Frame;
 
@@ -25,6 +25,11 @@ struct xRuntime {
 	Heap  *heap;
 };
 
+Stack *Runtime_GetStack(Runtime *runtime)
+{
+	return Stack_Copy(runtime->stack, 1);
+}
+
 Heap *Runtime_GetHeap(Runtime *runtime)
 {
 	return runtime->heap;

src/runtime/runtime.h

@@ -2,6 +2,7 @@
 #define RUNTIME_H
 #include <stdio.h> // meh.. just for the definition of FILE.
 #include "../utils/error.h"
+#include "../utils/stack.h"
 #include "../objects/objects.h"
 #include "../common/executable.h"
 
@@ -11,6 +12,7 @@ void 		Runtime_Free(Runtime *runtime);
 _Bool 		Runtime_Pop(Runtime *runtime, Error *error, unsigned int n);
 _Bool 		Runtime_Push(Runtime *runtime, Error *error, Object *obj);
 Heap*		Runtime_GetHeap(Runtime *runtime);
+Stack*		Runtime_GetStack(Runtime *runtime);
 Object*		Runtime_GetBuiltins(Runtime *runtime, Error *error);
 int 		Runtime_GetCurrentIndex(Runtime *runtime);
 Executable *Runtime_GetCurrentExecutable(Runtime *runtime);

src/utils/stack.c

@@ -1,12 +1,20 @@
+#include <stdint.h>
 #include <stdlib.h>
 #include "stack.h"
 #include "defs.h"
 
 struct xStack {
-	unsigned int size, used;
-	void *body[];
+	unsigned int size, 
+				 used;
+	int 		 refs;
+	void 		*body[];
 };
 
+_Bool Stack_IsReadOnlyCopy(Stack *s)
+{
+	return (uintptr_t) s & (uintptr_t) 1;
+}
+
 void *Stack_New(int size)
 {
 	if(size < 0)
@@ -17,15 +25,26 @@ void *Stack_New(int size)
 	if(s == NULL)
 		return NULL;
 
+	assert((intptr_t) s % 8 == 0);
+
 	s->size = size;
 	s->used = 0;
+	s->refs = 1;
 	return s;
 }
 
+static Stack *unmark(Stack *s)
+{
+	return (Stack*) ((intptr_t) s & ~ (intptr_t) 1);
+}
+
 void *Stack_Top(Stack *s, int n)
 {
 	assert(n <= 0);
 
+	// Remove readonly bit.
+	s = unmark(s);
+
 	if(s->used == 0)
 		return NULL;
 
@@ -37,6 +56,9 @@ void *Stack_Top(Stack *s, int n)
 
 _Bool Stack_Pop(Stack *s, unsigned int n)
 {
+	if(Stack_IsReadOnlyCopy(s))
+		return 0;
+
 	if(s->used < n)
 		return 0;
 
@@ -49,6 +71,9 @@ _Bool Stack_Push(Stack *s, void *item)
 	assert(s != NULL);
 	assert(item != NULL);
 
+	if(Stack_IsReadOnlyCopy(s))
+		return 0;
+
 	if(s->used == s->size)
 		return 0;
 
@@ -57,17 +82,51 @@ _Bool Stack_Push(Stack *s, void *item)
 	return 1;
 }
 
+Stack *Stack_Copy(Stack *s, _Bool readonly)
+{
+	if(Stack_IsReadOnlyCopy(s))
+		{
+			// Reference is readonly,
+			// so the copy must be
+			// readonly.
+			readonly = 1;
+
+			// Remove readonly bit.
+			s = unmark(s);
+		}
+
+	s->refs += 1;
+	
+	if(readonly)
+		return (Stack*) ((uintptr_t) s | (intptr_t) 1);
+	else
+		return s;
+}
+
 void Stack_Free(Stack *s)
 {
-	free(s);
+	// Remove readonly bit.
+	s = unmark(s);
+
+	s->refs -= 1;
+	assert(s->refs >= 0);
+
+	if(s->refs == 0)
+		free(s);
 }
 
 unsigned int Stack_Size(Stack *s)
 {
+	// Remove readonly bit.
+	s = unmark(s);
+
 	return s->used;
 }
 
 unsigned int Stack_Capacity(Stack *s)
 {
+	// Remove readonly bit.
+	s = unmark(s);
+
 	return s->size;
 }

src/utils/stack.h

@@ -7,5 +7,7 @@ _Bool 		 Stack_Pop(Stack *s, unsigned int n);
 _Bool 		 Stack_Push(Stack *s, void *item);
 void 		 Stack_Free(Stack *s);
 unsigned int Stack_Size(Stack *s);
+Stack 		*Stack_Copy(Stack *s, _Bool readonly);
 unsigned int Stack_Capacity(Stack *s);
+_Bool		 Stack_IsReadOnlyCopy(Stack *s);
 #endif