py: Fix compiling and decoding of *args at large arg positions.
There were two issues with the existing code: 1. "1 << i" is computed as a 32-bit number so would overflow when executed on 64-bit machines (when mp_uint_t is 64-bit). This meant that *args beyond 32 positions would not be handled correctly. 2. star_args must fit as a positive small int so that it is encoded correctly in the emitted code. MP_SMALL_INT_BITS is too big because it overflows a small int by 1 bit. MP_SMALL_INT_BITS - 1 does not work because it produces a signed small int which is then sign extended when extracted (even by mp_obj_get_int_truncated), and this sign extension means that any position arg after *args is also treated as a star-arg. So the maximum bit position is MP_SMALL_INT_BITS - 2. This means that MP_OBJ_SMALL_INT_VALUE() can be used instead of mp_obj_get_int_truncated() to get the value of star_args. These issues are fixed by this commit, and a test added. Signed-off-by: Damien George <damien@micropython.org>
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@ -2408,9 +2408,9 @@ STATIC void compile_trailer_paren_helper(compiler_t *comp, mp_parse_node_t pn_ar
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return;
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}
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#if MICROPY_DYNAMIC_COMPILER
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if (i > mp_dynamic_compiler.small_int_bits)
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if (i >= (size_t)mp_dynamic_compiler.small_int_bits - 1)
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#else
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if (i > MP_SMALL_INT_BITS)
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if (i >= MP_SMALL_INT_BITS - 1)
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#endif
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{
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// If there are not enough bits in a small int to fit the flag, then we consider
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@ -2419,7 +2419,7 @@ STATIC void compile_trailer_paren_helper(compiler_t *comp, mp_parse_node_t pn_ar
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return;
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}
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star_flags |= MP_EMIT_STAR_FLAG_SINGLE;
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star_args |= 1 << i;
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star_args |= (mp_uint_t)1 << i;
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compile_node(comp, pns_arg->nodes[0]);
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n_positional++;
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} else if (MP_PARSE_NODE_STRUCT_KIND(pns_arg) == PN_arglist_dbl_star) {
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@ -702,7 +702,7 @@ void mp_call_prepare_args_n_kw_var(bool have_self, size_t n_args_n_kw, const mp_
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}
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size_t n_args = n_args_n_kw & 0xff;
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size_t n_kw = (n_args_n_kw >> 8) & 0xff;
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mp_uint_t star_args = mp_obj_get_int_truncated(args[n_args + 2 * n_kw]);
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mp_uint_t star_args = MP_OBJ_SMALL_INT_VALUE(args[n_args + 2 * n_kw]);
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DEBUG_OP_printf("call method var (fun=%p, self=%p, n_args=%u, n_kw=%u, args=%p, map=%u)\n", fun, self, n_args, n_kw, args, star_args);
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@ -720,7 +720,7 @@ void mp_call_prepare_args_n_kw_var(bool have_self, size_t n_args_n_kw, const mp_
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if (star_args != 0) {
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for (size_t i = 0; i < n_args; i++) {
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if (star_args & (1 << i)) {
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if ((star_args >> i) & 1) {
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mp_obj_t len = mp_obj_len_maybe(args[i]);
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if (len != MP_OBJ_NULL) {
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// -1 accounts for 1 of n_args occupied by this arg
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@ -773,7 +773,7 @@ void mp_call_prepare_args_n_kw_var(bool have_self, size_t n_args_n_kw, const mp_
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for (size_t i = 0; i < n_args; i++) {
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mp_obj_t arg = args[i];
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if (star_args & (1 << i)) {
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if ((star_args >> i) & 1) {
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// star arg
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if (mp_obj_is_type(arg, &mp_type_tuple) || mp_obj_is_type(arg, &mp_type_list)) {
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// optimise the case of a tuple and list
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36
tests/stress/fun_call_limit.py
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36
tests/stress/fun_call_limit.py
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@ -0,0 +1,36 @@
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# Test the limit of the number of arguments to a function call.
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# This currently tests the case of *args after many positional args.
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def f(*args):
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return len(args)
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def test(n):
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pos_args = ",".join(str(i) for i in range(n))
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s = "f({}, *(100, 101), 102, 103)".format(pos_args)
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try:
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return eval(s)
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except SyntaxError:
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return "SyntaxError"
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# If the port has at least 32-bits then this test should pass.
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print(test(29))
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# This test should fail on all ports (overflows a small int).
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print(test(70))
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# Check that there is a correct transition to the limit of too many args before *args.
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reached_limit = False
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for i in range(30, 70):
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result = test(i)
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if reached_limit:
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if result != "SyntaxError":
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print("FAIL")
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else:
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if result == "SyntaxError":
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reached_limit = True
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else:
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if result != i + 4:
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print("FAIL")
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2
tests/stress/fun_call_limit.py.exp
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2
tests/stress/fun_call_limit.py.exp
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@ -0,0 +1,2 @@
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33
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SyntaxError
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