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py/vm: Prevent array bound warning when using -MP_OBJ_ITER_BUF_NSLOTS.

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This warning can happen on clang 13.0.1 building mpy-cross:

../py/vm.c:748:25: error: array index -3 refers past the last possible
  element for an array in 64-bit address space containing 64-bit (8-byte)
  elements (max possible 2305843009213693952 elements)
  [-Werror,-Warray-bounds]
                        sp[-MP_OBJ_ITER_BUF_NSLOTS + 1] = MP_OBJ_NULL;
                        ^  ~~~~~~~~~~~~~~~~~~~~~~~~~~~

Using pointer access instead of array access works around this warning.

Fixes issue #8467.

Signed-off-by: Damien George <damien@micropython.org>
This commit is contained in:
Damien George 2022-03-31 10:57:34 +11:00 committed by Jeff Epler
parent faca1ec3bf
commit a43cfdd274
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GPG Key ID: D5BF15AB975AB4DE
1 changed files with 4 additions and 4 deletions
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py/vm.c
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@ -821,8 +821,8 @@ unwind_jump:;
obj = mp_getiter(obj, iter_buf); obj = mp_getiter(obj, iter_buf);
if (obj != MP_OBJ_FROM_PTR(iter_buf)) { if (obj != MP_OBJ_FROM_PTR(iter_buf)) {
// Iterator didn't use the stack so indicate that with MP_OBJ_NULL. // Iterator didn't use the stack so indicate that with MP_OBJ_NULL.
sp[-MP_OBJ_ITER_BUF_NSLOTS + 1] = MP_OBJ_NULL; *(sp - MP_OBJ_ITER_BUF_NSLOTS + 1) = MP_OBJ_NULL;
sp[-MP_OBJ_ITER_BUF_NSLOTS + 2] = obj; *(sp - MP_OBJ_ITER_BUF_NSLOTS + 2) = obj;
} }
DISPATCH(); DISPATCH();
} }
@ -833,8 +833,8 @@ unwind_jump:;
DECODE_ULABEL; // the jump offset if iteration finishes; for labels are always forward DECODE_ULABEL; // the jump offset if iteration finishes; for labels are always forward
code_state->sp = sp; code_state->sp = sp;
mp_obj_t obj; mp_obj_t obj;
if (sp[-MP_OBJ_ITER_BUF_NSLOTS + 1] == MP_OBJ_NULL) { if (*(sp - MP_OBJ_ITER_BUF_NSLOTS + 1) == MP_OBJ_NULL) {
obj = sp[-MP_OBJ_ITER_BUF_NSLOTS + 2]; obj = *(sp - MP_OBJ_ITER_BUF_NSLOTS + 2);
} else { } else {
obj = MP_OBJ_FROM_PTR(&sp[-MP_OBJ_ITER_BUF_NSLOTS + 1]); obj = MP_OBJ_FROM_PTR(&sp[-MP_OBJ_ITER_BUF_NSLOTS + 1]);
} }