debugger: add finish command

Add finish (fin) command which resumes execution until returning from
the current function.

include/debugger.h

@@ -64,6 +64,7 @@ bool dbg_set_function_breakpoint(const char *_name, void(*cb)(struct breakpoint*
 bool dbg_set_address_breakpoint(uint32_t address, void(*cb)(struct breakpoint*), void *data);
 bool dbg_set_step_over_breakpoint(void);
 bool dbg_set_step_into_breakpoint(void);
+bool dbg_set_finish_breakpoint(void);
 void dbg_print_frame(unsigned no);
 void dbg_print_stack_trace(void);
 void dbg_print_stack(void);

src/debug.c

@@ -341,6 +341,9 @@ static int32_t dbg_next_address(bool into, int *call_index)
 
 bool dbg_set_step_over_breakpoint(void)
 {
+	if (instr_ptr <= 0)
+		return false;
+
 	int call_index;
 	int32_t address = dbg_next_address(false, &call_index);
 	if (address < 0)
@@ -351,6 +354,9 @@ bool dbg_set_step_over_breakpoint(void)
 
 bool dbg_set_step_into_breakpoint(void)
 {
+	if (instr_ptr <= 0)
+		return false;
+
 	int call_index;
 	int32_t address = dbg_next_address(true, &call_index);
 	if (address < 0)
@@ -359,6 +365,19 @@ bool dbg_set_step_into_breakpoint(void)
 	return true;
 }
 
+bool dbg_set_finish_breakpoint(void)
+{
+	if (call_stack_ptr < 2)
+		return false;
+
+	int32_t address = call_stack[call_stack_ptr-1].return_address;
+	// XXX: VM_RETURN
+	if (address < 0)
+		return false;
+	dbg_set_step_breakpoint(address, call_stack_ptr - 1);
+	return true;
+}
+
 static void _dbg_handle_breakpoint(void *data)
 {
 	struct breakpoint *bp = data;
@@ -549,6 +568,9 @@ struct string *dbg_value_to_string(struct ain_type *type, union vm_value value,
 // Rewind to DASM_REWIND instructions before the current instruction pointer.
 static bool dbg_init_dasm(struct dasm *dasm)
 {
+	if (call_stack_ptr < 1)
+		goto error;
+
 	unsigned addr_i = 0;
 	size_t addr[DASM_REWIND] = {0};
 	int fno = call_stack[call_stack_ptr-1].fno;
@@ -759,6 +781,11 @@ static bool dasm_print_finished(struct dasm *dasm, int dasm_i)
 
 void dbg_print_vm_state(void)
 {
+	if (call_stack_ptr < 1) {
+		DBG_ERROR("VM not running");
+		return;
+	}
+
 	puts("");
 	puts("     Stack           Disassembly");
 	puts("-----------------    -----------");

src/debugger_cmd.c

@@ -183,19 +183,31 @@ static void dbg_cmd_scene(unsigned nr_args, char **args)
 
 static void dbg_cmd_next(unsigned nr_args, char **args)
 {
-	if (!dbg_set_step_over_breakpoint())
+	if (!dbg_set_step_over_breakpoint()) {
 		DBG_ERROR("Can't step over this instruction");
-	else
-		stepping = true;
+		return;
+	}
+	stepping = true;
 	dbg_continue();
 }
 
 static void dbg_cmd_step(unsigned nr_args, char **args)
 {
-	if (!dbg_set_step_into_breakpoint())
+	if (!dbg_set_step_into_breakpoint()) {
 		DBG_ERROR("Can't step into this instruction");
-	else
-		stepping = true;
+		return;
+	}
+	stepping = true;
+	dbg_continue();
+}
+
+static void dbg_cmd_finish(unsigned nr_args, char **args)
+{
+	if (!dbg_set_finish_breakpoint()) {
+		DBG_ERROR("Can't set finish breakpoint from this location");
+		return;
+	}
+	stepping = true;
 	dbg_continue();
 }
 
@@ -216,6 +228,7 @@ static struct dbg_cmd dbg_default_commands[] = {
 	{ "backtrace",  "bt",  "- Display stack trace",                  0, 0, dbg_cmd_backtrace },
 	{ "breakpoint", "bp",  "<function-or-address> - Set breakpoint", 1, 1, dbg_cmd_breakpoint },
 	{ "continue",   "c",   "- Resume execution",                     0, 0, dbg_cmd_continue },
+	{ "finish",     "fin", "- Step back to the caller function",     0, 0, dbg_cmd_finish },
 	{ "frame",      "f",   "<frame-number> - Set the current frame", 1, 1, dbg_cmd_frame },
 	{ "locals",     "l",   "[frame-number] - Print local variables", 0, 1, dbg_cmd_locals },
 	{ "log",        NULL,  "<function-name> - Log function calls",   1, 1, dbg_cmd_log },