py: Make sure that static emg-exc-buffer is aligned to size of mp_obj_t.

This buffer is used to allocate objects temporarily, and such objects
require that their underlying memory be correctly aligned for their data
type.  Aligning for mp_obj_t should be sufficient for emergency exceptions,
but in general the memory buffer should aligned to the maximum alignment of
the machine (eg on a 32-bit machine with mp_obj_t being 4 bytes, a double
may not be correctly aligned).

This patch fixes a bug for certain nan-boxing builds, where mp_obj_t is 8
bytes and must be aligned to 8 bytes (even though the machine is 32 bit).

1 files changed, 2 insertions, 2 deletions

diff --git a/py/mpstate.h b/py/mpstate.h
index 0134dd8e8..2b8f29a6a 100644
--- a/py/mpstate.h
+++ b/py/mpstate.h
@@ -120,8 +120,8 @@ typedef struct _mp_state_vm_t {
     // memory for exception arguments if we can't allocate RAM
     #if MICROPY_ENABLE_EMERGENCY_EXCEPTION_BUF
     #if MICROPY_EMERGENCY_EXCEPTION_BUF_SIZE > 0
-    // statically allocated buf
-    byte mp_emergency_exception_buf[MICROPY_EMERGENCY_EXCEPTION_BUF_SIZE];
+    // statically allocated buf (needs to be aligned to mp_obj_t)
+    mp_obj_t mp_emergency_exception_buf[MICROPY_EMERGENCY_EXCEPTION_BUF_SIZE / sizeof(mp_obj_t)];
     #else
     // dynamically allocated buf
     byte *mp_emergency_exception_buf;