py: Get optional VM stack overflow check compiling and working again.

Changes to the layout of the bytecode header meant that this debug code was
no longer compiling.  This is now fixed and a new compile-time option is
introduced, MICROPY_DEBUG_VM_STACK_OVERFLOW, to turn on this feature (which
is disabled by default).  This option is needed because more than one file
needs to cooperate to make this check work.

1 files changed, 4 insertions, 0 deletions

diff --git a/py/emitbc.c b/py/emitbc.c
index 98e1d1bde..6a46cfb59 100644
--- a/py/emitbc.c
+++ b/py/emitbc.c
@@ -331,6 +331,10 @@ void mp_emit_bc_start_pass(emit_t *emit, pass_kind_t pass, scope_t *scope) {
             // the highest slot in the state (fastn[0], see vm.c).
             n_state = 1;
         }
+        #if MICROPY_DEBUG_VM_STACK_OVERFLOW
+        // An extra slot in the stack is needed to detect VM stack overflow
+        n_state += 1;
+        #endif
         emit_write_code_info_uint(emit, n_state);
         emit_write_code_info_uint(emit, scope->exc_stack_size);
     }