Implement REPL.

py/compile.c

@@ -44,11 +44,14 @@ typedef struct _compiler_t {
     qstr qstr___doc__;
     qstr qstr_assertion_error;
     qstr qstr_micropython;
+    qstr qstr_byte_code;
     qstr qstr_native;
     qstr qstr_viper;
     qstr qstr_asm_thumb;
 
+    bool is_repl;
     pass_kind_t pass;
+    bool had_error; // try to keep compiler clean from nlr
 
     int next_label;
 
@@ -196,7 +199,7 @@ static int comp_next_label(compiler_t *comp) {
 }
 
 static scope_t *scope_new_and_link(compiler_t *comp, scope_kind_t kind, py_parse_node_t pn, uint emit_options) {
-    scope_t *scope = scope_new(kind, pn, rt_get_new_unique_code_id(), emit_options);
+    scope_t *scope = scope_new(kind, pn, rt_get_unique_code_id(kind == SCOPE_MODULE), emit_options);
     scope->parent = comp->scope_cur;
     scope->next = NULL;
     if (comp->scope_head == NULL) {
@@ -855,7 +858,8 @@ static bool compile_built_in_decorator(compiler_t *comp, int name_len, py_parse_
     }
 
     qstr attr = PY_PARSE_NODE_LEAF_ARG(name_nodes[1]);
-    if (0) {
+    if (attr == comp->qstr_byte_code) {
+        *emit_options = EMIT_OPT_BYTE_CODE;
 #if MICROPY_EMIT_NATIVE
     } else if (attr == comp->qstr_native) {
         *emit_options = EMIT_OPT_NATIVE_PYTHON;
@@ -1046,7 +1050,13 @@ void compile_continue_stmt(compiler_t *comp, py_parse_node_struct_t *pns) {
 }
 
 void compile_return_stmt(compiler_t *comp, py_parse_node_struct_t *pns) {
+    if (comp->scope_cur->kind != SCOPE_FUNCTION) {
+        printf("SyntaxError: 'return' outside function\n");
+        comp->had_error = true;
+        return;
+    }
     if (PY_PARSE_NODE_IS_NULL(pns->nodes[0])) {
+        // no argument to 'return', so return None
         EMIT(load_const_tok, PY_TOKEN_KW_NONE);
     } else if (PY_PARSE_NODE_IS_STRUCT_KIND(pns->nodes[0], PN_test_if_expr)) {
         // special case when returning an if-expression; to match CPython optimisation
@@ -1566,11 +1576,21 @@ void compile_with_stmt(compiler_t *comp, py_parse_node_struct_t *pns) {
 
 void compile_expr_stmt(compiler_t *comp, py_parse_node_struct_t *pns) {
     if (PY_PARSE_NODE_IS_NULL(pns->nodes[1])) {
-        if (PY_PARSE_NODE_IS_LEAF(pns->nodes[0]) && !PY_PARSE_NODE_IS_ID(pns->nodes[0])) {
+        if (comp->is_repl && comp->scope_cur->kind == SCOPE_MODULE) {
-            // do nothing with a lonely constant
+            // for REPL, evaluate then print the expression
+            EMIT(load_id, qstr_from_str_static("__repl_print__"));
+            compile_node(comp, pns->nodes[0]);
+            EMIT(call_function, 1, 0, false, false);
+            EMIT(pop_top);
+
         } else {
-            compile_node(comp, pns->nodes[0]); // just an expression
+            // for non-REPL, evaluate then discard the expression
-            EMIT(pop_top); // discard last result since this is a statement and leaves nothing on the stack
+            if (PY_PARSE_NODE_IS_LEAF(pns->nodes[0]) && !PY_PARSE_NODE_IS_ID(pns->nodes[0])) {
+                // do nothing with a lonely constant
+            } else {
+                compile_node(comp, pns->nodes[0]); // just an expression
+                EMIT(pop_top); // discard last result since this is a statement and leaves nothing on the stack
+            }
         }
     } else {
         py_parse_node_struct_t *pns1 = (py_parse_node_struct_t*)pns->nodes[1];
@@ -2287,6 +2307,7 @@ void compile_node(compiler_t *comp, py_parse_node_t pn) {
             case PY_PARSE_NODE_TOKEN:
                 if (arg == PY_TOKEN_NEWLINE) {
                     // this can occur when file_input lets through a NEWLINE (eg if file starts with a newline)
+                    // or when single_input lets through a NEWLINE (user enters a blank line)
                     // do nothing
                 } else {
                   EMIT(load_const_tok, arg);
@@ -2299,7 +2320,7 @@ void compile_node(compiler_t *comp, py_parse_node_t pn) {
         compile_function_t f = compile_function[PY_PARSE_NODE_STRUCT_KIND(pns)];
         if (f == NULL) {
             printf("node %u cannot be compiled\n", (uint)PY_PARSE_NODE_STRUCT_KIND(pns));
-            parse_node_show(pn, 0);
+            py_parse_node_show(pn, 0);
             assert(0);
         } else {
             f(comp, pns);
@@ -2481,14 +2502,17 @@ void compile_scope(compiler_t *comp, scope_t *scope, pass_kind_t pass) {
         scope->stack_size = 0;
     }
 
+#if MICROPY_EMIT_CPYTHON
     if (comp->pass == PASS_3) {
-        //printf("----\n");
         scope_print_info(scope);
     }
+#endif
 
     // compile
     if (scope->kind == SCOPE_MODULE) {
-        check_for_doc_string(comp, scope->pn);
+        if (!comp->is_repl) {
+            check_for_doc_string(comp, scope->pn);
+        }
         compile_node(comp, scope->pn);
         EMIT(load_const_tok, PY_TOKEN_KW_NONE);
         EMIT(return_value);
@@ -2731,7 +2755,7 @@ void compile_scope_compute_things(compiler_t *comp, scope_t *scope) {
     }
 }
 
-void py_compile(py_parse_node_t pn) {
+bool py_compile(py_parse_node_t pn, bool is_repl) {
     compiler_t *comp = m_new(compiler_t, 1);
 
     comp->qstr___class__ = qstr_from_str_static("__class__");
@@ -2742,10 +2766,14 @@ void py_compile(py_parse_node_t pn) {
     comp->qstr___doc__ = qstr_from_str_static("__doc__");
     comp->qstr_assertion_error = qstr_from_str_static("AssertionError");
     comp->qstr_micropython = qstr_from_str_static("micropython");
+    comp->qstr_byte_code = qstr_from_str_static("byte_code");
     comp->qstr_native = qstr_from_str_static("native");
     comp->qstr_viper = qstr_from_str_static("viper");
     comp->qstr_asm_thumb = qstr_from_str_static("asm_thumb");
 
+    comp->is_repl = is_repl;
+    comp->had_error = false;
+
     comp->break_label = 0;
     comp->continue_label = 0;
     comp->except_nest_level = 0;
@@ -2764,7 +2792,7 @@ void py_compile(py_parse_node_t pn) {
     comp->emit_inline_asm = NULL;
     comp->emit_inline_asm_method_table = NULL;
     uint max_num_labels = 0;
-    for (scope_t *s = comp->scope_head; s != NULL; s = s->next) {
+    for (scope_t *s = comp->scope_head; s != NULL && !comp->had_error; s = s->next) {
         if (false) {
 #if MICROPY_EMIT_INLINE_THUMB
         } else if (s->emit_options == EMIT_OPT_ASM_THUMB) {
@@ -2781,7 +2809,7 @@ void py_compile(py_parse_node_t pn) {
     }
 
     // compute some things related to scope and identifiers
-    for (scope_t *s = comp->scope_head; s != NULL; s = s->next) {
+    for (scope_t *s = comp->scope_head; s != NULL && !comp->had_error; s = s->next) {
         compile_scope_compute_things(comp, s);
     }
 
@@ -2796,7 +2824,7 @@ void py_compile(py_parse_node_t pn) {
 #if MICROPY_EMIT_INLINE_THUMB
     emit_inline_asm_t *emit_inline_thumb = NULL;
 #endif
-    for (scope_t *s = comp->scope_head; s != NULL; s = s->next) {
+    for (scope_t *s = comp->scope_head; s != NULL && !comp->had_error; s = s->next) {
         if (false) {
             // dummy
 
@@ -2857,4 +2885,6 @@ void py_compile(py_parse_node_t pn) {
     }
 
     m_free(comp);
+
+    return !comp->had_error;
 }

py/compile.h

@@ -1 +1 @@
-void py_compile(py_parse_node_t pn);
+bool py_compile(py_parse_node_t pn, bool is_repl);

py/parse.c

@@ -128,7 +128,7 @@ py_parse_node_struct_t *parse_node_new_struct(int rule_id, int num_args) {
     return pn;
 }
 
-void parse_node_show(py_parse_node_t pn, int indent) {
+void py_parse_node_show(py_parse_node_t pn, int indent) {
     for (int i = 0; i < indent; i++) {
         printf(" ");
     }
@@ -155,7 +155,7 @@ void parse_node_show(py_parse_node_t pn, int indent) {
         printf("rule(%u) (n=%d)\n", (uint)PY_PARSE_NODE_STRUCT_KIND(pns2), n);
 #endif
         for (int i = 0; i < n; i++) {
-            parse_node_show(pns2->nodes[i], indent + 2);
+            py_parse_node_show(pns2->nodes[i], indent + 2);
         }
     }
 }
@@ -164,7 +164,7 @@ void parse_node_show(py_parse_node_t pn, int indent) {
 static void result_stack_show(parser_t *parser) {
     printf("result stack, most recent first\n");
     for (int i = parser->result_stack_top - 1; i >= 0; i--) {
-        parse_node_show(parser->result_stack[i], 0);
+        py_parse_node_show(parser->result_stack[i], 0);
     }
 }
 */
@@ -251,8 +251,7 @@ static void push_result_rule(parser_t *parser, rule_t *rule, int num_args) {
     push_result_node(parser, (py_parse_node_t)pn);
 }
 
-py_parse_node_t py_parse(py_lexer_t *lex, int wanted_rule) {
+py_parse_node_t py_parse(py_lexer_t *lex, py_parse_input_kind_t input_kind) {
-    wanted_rule = RULE_file_input;
     parser_t *parser = m_new(parser_t, 1);
     parser->rule_stack_alloc = 64;
     parser->rule_stack_top = 0;
@@ -261,7 +260,13 @@ py_parse_node_t py_parse(py_lexer_t *lex, int wanted_rule) {
     parser->result_stack = m_new(py_parse_node_t, 1000);
     parser->result_stack_top = 0;
 
-    push_rule(parser, rules[wanted_rule], 0);
+    int top_level_rule;
+    switch (input_kind) {
+        case PY_PARSE_SINGLE_INPUT: top_level_rule = RULE_single_input; break;
+        //case PY_PARSE_EVAL_INPUT: top_level_rule = RULE_eval_input; break;
+        default: top_level_rule = RULE_file_input;
+    }
+    push_rule(parser, rules[top_level_rule], 0);
 
     uint n, i;
     bool backtrack = false;

py/parse.h

@@ -54,6 +54,12 @@ typedef struct _py_parse_node_struct_t {
 
 py_parse_node_t py_parse_node_new_leaf(machine_int_t kind, machine_int_t arg);
 
-void parse_node_show(py_parse_node_t pn, int indent);
+void py_parse_node_show(py_parse_node_t pn, int indent);
 
-py_parse_node_t py_parse(struct _py_lexer_t *lex, int wanted_rule);
+typedef enum {
+    PY_PARSE_SINGLE_INPUT,
+    PY_PARSE_FILE_INPUT,
+    PY_PARSE_EVAL_INPUT,
+} py_parse_input_kind_t;
+
+py_parse_node_t py_parse(struct _py_lexer_t *lex, py_parse_input_kind_t input_kind);

py/runtime.c

@@ -192,11 +192,7 @@ void py_map_init(py_map_t *map, py_map_kind_t kind, int n) {
     map->kind = kind;
     map->alloc = get_doubling_prime_greater_or_equal_to(n + 1);
     map->used = 0;
-    map->table = m_new(py_map_elem_t, map->alloc);
+    map->table = m_new0(py_map_elem_t, map->alloc);
-    for (int i = 0; i < map->alloc; i++) {
-        map->table[i].key = NULL;
-        map->table[i].value = NULL;
-    }
 }
 
 py_map_t *py_map_new(py_map_kind_t kind, int n) {
@@ -205,9 +201,15 @@ py_map_t *py_map_new(py_map_kind_t kind, int n) {
     return map;
 }
 
-int py_obj_hash(py_obj_t o_in) {
+machine_int_t py_obj_hash(py_obj_t o_in) {
-    if (IS_SMALL_INT(o_in)) {
+    if (o_in == py_const_false) {
+        return 0; // needs to hash to same as the integer 0, since False==0
+    } else if (o_in == py_const_true) {
+        return 1; // needs to hash to same as the integer 1, since True==1
+    } else if (IS_SMALL_INT(o_in)) {
         return FROM_SMALL_INT(o_in);
+    } else if (IS_O(o_in, O_CONST)) {
+        return (machine_int_t)o_in;
     } else if (IS_O(o_in, O_STR)) {
         return ((py_obj_base_t*)o_in)->u_str;
     } else {
@@ -216,11 +218,32 @@ int py_obj_hash(py_obj_t o_in) {
     }
 }
 
+// this function implements the '==' operator (and so the inverse of '!=')
+// from the python language reference:
+// "The objects need not have the same type. If both are numbers, they are converted
+// to a common type. Otherwise, the == and != operators always consider objects of
+// different types to be unequal."
+// note also that False==0 and True==1 are true expressions
 bool py_obj_equal(py_obj_t o1, py_obj_t o2) {
     if (o1 == o2) {
         return true;
-    } else if (IS_SMALL_INT(o1) && IS_SMALL_INT(o2)) {
+    } else if (IS_SMALL_INT(o1) || IS_SMALL_INT(o2)) {
-        return false;
+        if (IS_SMALL_INT(o1) && IS_SMALL_INT(o2)) {
+            return false;
+        } else {
+            if (IS_SMALL_INT(o2)) {
+                py_obj_t temp = o1; o1 = o2; o2 = temp;
+            }
+            // o1 is the SMALL_INT, o2 is not
+            py_small_int_t val = FROM_SMALL_INT(o1);
+            if (o2 == py_const_false) {
+                return val == 0;
+            } else if (o2 == py_const_true) {
+                return val == 1;
+            } else {
+                return false;
+            }
+        }
     } else if (IS_O(o1, O_STR) && IS_O(o2, O_STR)) {
         return ((py_obj_base_t*)o1)->u_str == ((py_obj_base_t*)o2)->u_str;
     } else {
@@ -249,7 +272,7 @@ py_map_elem_t* py_map_lookup_helper(py_map_t *map, py_obj_t index, bool add_if_n
                     py_map_elem_t *old_table = map->table;
                     map->alloc = get_doubling_prime_greater_or_equal_to(map->alloc + 1);
                     map->used = 0;
-                    map->table = m_new(py_map_elem_t, map->alloc);
+                    map->table = m_new0(py_map_elem_t, map->alloc);
                     for (int i = 0; i < old_alloc; i++) {
                         if (old_table[i].key != NULL) {
                             py_map_lookup_helper(map, old_table[i].key, true)->value = old_table[i].value;
@@ -268,9 +291,11 @@ py_map_elem_t* py_map_lookup_helper(py_map_t *map, py_obj_t index, bool add_if_n
             }
         } else if (elem->key == index || (is_map_py_obj && py_obj_equal(elem->key, index))) {
             // found it
+            /* it seems CPython does not replace the index; try x={True:'true'};x[1]='one';x
             if (add_if_not_found) {
                 elem->key = index;
             }
+            */
             return elem;
         } else {
             // not yet found, keep searching in this table
@@ -395,6 +420,7 @@ static qstr q___build_class__;
 static qstr q___next__;
 static qstr q_AttributeError;
 static qstr q_IndexError;
+static qstr q_KeyError;
 static qstr q_NameError;
 static qstr q_TypeError;
 
@@ -431,6 +457,14 @@ static py_code_t *unique_codes;
 py_obj_t fun_list_append;
 py_obj_t fun_gen_instance_next;
 
+py_obj_t py_builtin___repl_print__(py_obj_t o) {
+    if (o != py_const_none) {
+        py_obj_print(o);
+        printf("\n");
+    }
+    return py_const_none;
+}
+
 py_obj_t py_builtin_print(py_obj_t o) {
     if (IS_O(o, O_STR)) {
         // special case, print string raw
@@ -492,6 +526,7 @@ void rt_init() {
     q___next__ = qstr_from_str_static("__next__");
     q_AttributeError = qstr_from_str_static("AttributeError");
     q_IndexError = qstr_from_str_static("IndexError");
+    q_KeyError = qstr_from_str_static("KeyError");
     q_NameError = qstr_from_str_static("NameError");
     q_TypeError = qstr_from_str_static("TypeError");
 
@@ -505,12 +540,13 @@ void rt_init() {
     py_qstr_map_lookup(map_globals, qstr_from_str_static("__name__"), true)->value = py_obj_new_str(qstr_from_str_static("__main__"));
 
     py_map_init(&map_builtins, MAP_QSTR, 3);
+    py_qstr_map_lookup(&map_builtins, qstr_from_str_static("__repl_print__"), true)->value = rt_make_function_1(py_builtin___repl_print__);
     py_qstr_map_lookup(&map_builtins, q_print, true)->value = rt_make_function_1(py_builtin_print);
     py_qstr_map_lookup(&map_builtins, q_len, true)->value = rt_make_function_1(py_builtin_len);
     py_qstr_map_lookup(&map_builtins, q___build_class__, true)->value = rt_make_function_2(py_builtin___build_class__);
     py_qstr_map_lookup(&map_builtins, qstr_from_str_static("range"), true)->value = rt_make_function_1(py_builtin_range);
 
-    next_unique_code_id = 1;
+    next_unique_code_id = 2; // 1 is reserved for the __main__ module scope
     unique_codes = NULL;
 
     fun_list_append = rt_make_function_2(rt_list_append);
@@ -529,8 +565,12 @@ void rt_deinit() {
 #endif
 }
 
-int rt_get_new_unique_code_id() {
+int rt_get_unique_code_id(bool is_main_module) {
-    return next_unique_code_id++;
+    if (is_main_module) {
+        return 1;
+    } else {
+        return next_unique_code_id++;
+    }
 }
 
 static void alloc_unique_codes() {
@@ -896,8 +936,17 @@ py_obj_t rt_binary_op(int op, py_obj_t lhs, py_obj_t rhs) {
     DEBUG_OP_printf("binary %d %p %p\n", op, lhs, rhs);
     if (op == RT_BINARY_OP_SUBSCR) {
         if ((IS_O(lhs, O_TUPLE) || IS_O(lhs, O_LIST))) {
+            // tuple/list load
             uint index = get_index(lhs, rhs);
             return ((py_obj_base_t*)lhs)->u_tuple_list.items[index];
+        } else if (IS_O(lhs, O_MAP)) {
+            // map load
+            py_map_elem_t *elem = py_map_lookup(lhs, rhs, false);
+            if (elem == NULL) {
+                nlr_jump(py_obj_new_exception_2(q_KeyError, "<value>", NULL, NULL));
+            } else {
+                return elem->value;
+            }
         } else {
             assert(0);
         }
@@ -1409,16 +1458,16 @@ no_attr:
     dest[0] = NULL;
 }
 
-void rt_store_attr(py_obj_t base, qstr attr, py_obj_t val) {
+void rt_store_attr(py_obj_t base, qstr attr, py_obj_t value) {
-    DEBUG_OP_printf("store attr %p.%s <- %p\n", base, qstr_str(attr), val);
+    DEBUG_OP_printf("store attr %p.%s <- %p\n", base, qstr_str(attr), value);
     if (IS_O(base, O_OBJ)) {
         // logic: look in class locals (no add) then obj members (add) (TODO check this against CPython)
         py_obj_base_t *o = base;
         py_map_elem_t *elem = py_qstr_map_lookup(o->u_obj.class->u_class.locals, attr, false);
         if (elem != NULL) {
-            elem->value = val;
+            elem->value = value;
         } else {
-            elem = py_qstr_map_lookup(o->u_obj.class->u_class.locals, attr, true)->value = val;
+            elem = py_qstr_map_lookup(o->u_obj.class->u_class.locals, attr, true)->value = value;
         }
     } else {
         printf("?AttributeError: '%s' object has no attribute '%s'\n", py_obj_get_type_str(base), qstr_str(attr));
@@ -1427,6 +1476,7 @@ void rt_store_attr(py_obj_t base, qstr attr, py_obj_t val) {
 }
 
 void rt_store_subscr(py_obj_t base, py_obj_t index, py_obj_t value) {
+    DEBUG_OP_printf("store subscr %p[%p] <- %p\n", base, index, value);
     if (IS_O(base, O_LIST)) {
         // list store
         uint i = get_index(base, index);

py/runtime.h

@@ -91,7 +91,7 @@ extern py_obj_t py_const_stop_iteration; // special object indicating end of ite
 
 void rt_init();
 void rt_deinit();
-int rt_get_new_unique_code_id();
+int rt_get_unique_code_id(bool is_main_module);
 void rt_assign_byte_code(int unique_code_id, byte *code, uint len, int n_args, int n_locals, int n_stack, bool is_generator);
 void rt_assign_native_code(int unique_code_id, py_fun_t f, uint len, int n_args);
 void rt_assign_inline_asm_code(int unique_code_id, py_fun_t f, uint len, int n_args);

unix/Makefile

@@ -31,7 +31,7 @@ PY_O = \
 	vm.o \
 
 OBJ = $(addprefix $(BUILD)/, $(SRC_C:.c=.o) $(PY_O))
-LIB =
+LIB = -lreadline
 PROG = py
 
 $(PROG): $(BUILD) $(OBJ)

unix/main.c

@@ -10,61 +10,152 @@
 #include "compile.h"
 #include "runtime.h"
 
-int main(int argc, char **argv) {
+#include <readline/readline.h>
-    qstr_init();
-    rt_init();
 
-    if (argc != 2) {
+bool str_startswith_word(const char *str, const char *head) {
-        printf("usage: py <file>\n");
+    int i;
-        return 1;
+    for (i = 0; str[i] && head[i]; i++) {
+        if (str[i] != head[i]) {
+            return false;
+        }
     }
-    py_lexer_t *lex = py_lexer_from_file(argv[1]);
+    return head[i] == '\0' && (str[i] == '\0' || !g_unichar_isalpha(str[i]));
+}
+
+bool is_compound_stmt(const char *line) {
+    // TODO also "compound" if unmatched open bracket
+    return
+           str_startswith_word(line, "if")
+        || str_startswith_word(line, "while")
+        || str_startswith_word(line, "for")
+        || str_startswith_word(line, "true")
+        || str_startswith_word(line, "with")
+        || str_startswith_word(line, "def")
+        || str_startswith_word(line, "class")
+        || str_startswith_word(line, "@");
+}
+
+char *str_join(const char *s1, int sep_char, const char *s2) {
+    int l1 = strlen(s1);
+    int l2 = strlen(s2);
+    char *s = m_new(char, l1 + l2 + 2);
+    memcpy(s, s1, l1);
+    if (sep_char != 0) {
+        s[l1] = sep_char;
+        l1 += 1;
+    }
+    memcpy(s + l1, s2, l2);
+    return s;
+}
+
+void do_repl() {
+    for (;;) {
+        char *line = readline(">>> ");
+        if (line == NULL) {
+            // EOF
+            return;
+        }
+        if (is_compound_stmt(line)) {
+            for (;;) {
+                char *line2 = readline("... ");
+                if (line2 == NULL || strlen(line2) == 0) {
+                    break;
+                }
+                char *line3 = str_join(line, '\n', line2);
+                m_free(line);
+                m_free(line2);
+                line = line3;
+            }
+        }
+        py_lexer_t *lex = py_lexer_from_str_len("<stdin>", line, strlen(line), false);
+        py_parse_node_t pn = py_parse(lex, PY_PARSE_SINGLE_INPUT);
+        if (pn != PY_PARSE_NODE_NULL) {
+            //py_parse_node_show(pn, 0);
+            bool comp_ok = py_compile(pn, true);
+            if (comp_ok) {
+                py_obj_t module_fun = rt_make_function_from_id(1);
+                if (module_fun != py_const_none) {
+                    nlr_buf_t nlr;
+                    if (nlr_push(&nlr) == 0) {
+                        rt_call_function_0(module_fun);
+                        nlr_pop();
+                    } else {
+                        // uncaught exception
+                        py_obj_print((py_obj_t)nlr.ret_val);
+                        printf("\n");
+                    }
+                }
+            }
+        }
+    }
+}
+
+void do_file(const char *file) {
+    py_lexer_t *lex = py_lexer_from_file(file);
     //const char *pysrc = "def f():\n  x=x+1\n  print(42)\n";
     //py_lexer_t *lex = py_lexer_from_str_len("<>", pysrc, strlen(pysrc), false);
     if (lex == NULL) {
-        return 1;
+        return;
     }
 
     if (0) {
+        // just tokenise
         while (!py_lexer_is_kind(lex, PY_TOKEN_END)) {
             py_token_show(py_lexer_cur(lex));
             py_lexer_to_next(lex);
         }
+        py_lexer_free(lex);
+
     } else {
-        py_parse_node_t pn = py_parse(lex, 0);
+        // compile
+
+        py_parse_node_t pn = py_parse(lex, PY_PARSE_FILE_INPUT);
         if (pn != PY_PARSE_NODE_NULL) {
             //printf("----------------\n");
             //parse_node_show(pn, 0);
             //printf("----------------\n");
-            py_compile(pn);
+            bool comp_ok = py_compile(pn, false);
             //printf("----------------\n");
-        }
-    }
 
-    py_lexer_free(lex);
+            py_lexer_free(lex);
 
 #if !MICROPY_EMIT_CPYTHON
-    if (1) {
+            if (1 && comp_ok) {
-        // execute it
+                // execute it
-        py_obj_t module_fun = rt_make_function_from_id(1);
+                py_obj_t module_fun = rt_make_function_from_id(1);
-        if (module_fun != py_const_none) {
+                if (module_fun != py_const_none) {
-            nlr_buf_t nlr;
+                    nlr_buf_t nlr;
-            if (nlr_push(&nlr) == 0) {
+                    if (nlr_push(&nlr) == 0) {
-                py_obj_t ret = rt_call_function_0(module_fun);
+                        py_obj_t ret = rt_call_function_0(module_fun);
-                printf("done! got: ");
+                        printf("done! got: ");
-                py_obj_print(ret);
+                        py_obj_print(ret);
-                printf("\n");
+                        printf("\n");
-                nlr_pop();
+                        nlr_pop();
-            } else {
+                    } else {
-                // uncaught exception
+                        // uncaught exception
-                printf("exception: ");
+                        printf("exception: ");
-                py_obj_print((py_obj_t)nlr.ret_val);
+                        py_obj_print((py_obj_t)nlr.ret_val);
-                printf("\n");
+                        printf("\n");
+                    }
+                }
             }
+#endif
         }
     }
-#endif
+}
 
+int main(int argc, char **argv) {
+    qstr_init();
+    rt_init();
+
+    if (argc == 1) {
+        do_repl();
+    } else if (argc == 2) {
+        do_file(argv[1]);
+    } else {
+        printf("usage: py [<file>]\n");
+        return 1;
+    }
     rt_deinit();
 
     //printf("total bytes = %d\n", m_get_total_bytes_allocated());