diff --git a/py/vm.c b/py/vm.c
index 1c154007cafa3c8e460b267e2955d7261c6b820c..e42e54941ef049271b56c987051c3fc2c4564fcf 100644
--- a/py/vm.c
+++ b/py/vm.c
@@ -165,8 +165,6 @@ mp_vm_return_kind_t mp_execute_byte_code_2(const byte *code_info, const byte **i
mp_obj_t *fastn, mp_obj_t **sp_in_out,
mp_exc_stack_t *exc_stack, mp_exc_stack_t **exc_sp_in_out,
volatile mp_obj_t inject_exc) {
- // careful: be sure to declare volatile any variables read in the exception handler (written is ok, I think)
-
#if MICROPY_USE_COMPUTED_GOTOS
#include "vmentrytable.h"
#define DISPATCH() do { \
@@ -182,32 +180,43 @@ mp_vm_return_kind_t mp_execute_byte_code_2(const byte *code_info, const byte **i
#define ENTRY_DEFAULT default
#endif
- int op = 0;
- const byte *ip = *ip_in_out;
- mp_obj_t *sp = *sp_in_out;
- machine_uint_t unum;
- qstr qst;
- mp_obj_t obj1, obj2;
- nlr_buf_t nlr;
+ // nlr_raise needs to be implemented as a goto, so that the C compiler's flow analyser
+ // sees that it's possible for us to jump from the dispatch loop to the exception
+ // handler. Without this, the code may have a different stack layout in the dispatch
+ // loop and the exception handler, leading to very obscure bugs.
+ #define RAISE(o) do { nlr_pop(); nlr.ret_val = o; goto exception_handler; } while(0)
+ // variables that are visible to the exception handler (declared volatile)
volatile bool currently_in_except_block = MP_TAGPTR_TAG(*exc_sp_in_out); // 0 or 1, to detect nested exceptions
mp_exc_stack_t *volatile exc_sp = MP_TAGPTR_PTR(*exc_sp_in_out); // stack grows up, exc_sp points to top of stack
- const byte *volatile save_ip = ip; // this is so we can access ip in the exception handler without making ip volatile (which means the compiler can't keep it in a register in the main loop)
+ const byte *volatile save_ip = *ip_in_out; // this is so we can access ip in the exception handler without making ip volatile (which means the compiler can't keep it in a register in the main loop)
+ mp_obj_t *volatile save_sp = *sp_in_out; // this is so we can access sp in the exception handler when needed
// outer exception handling loop
for (;;) {
+ nlr_buf_t nlr;
outer_dispatch_loop:
if (nlr_push(&nlr) == 0) {
+ // local variables that are not visible to the exception handler
+ byte op = 0;
+ const byte *ip = *ip_in_out;
+ mp_obj_t *sp = *sp_in_out;
+ machine_uint_t unum;
+ qstr qst;
+ mp_obj_t obj1, obj2;
+
// If we have exception to inject, now that we finish setting up
// execution context, raise it. This works as if RAISE_VARARGS
// bytecode was executed.
// Injecting exc into yield from generator is a special case,
// handled by MP_BC_YIELD_FROM itself
if (inject_exc != MP_OBJ_NULL && *ip != MP_BC_YIELD_FROM) {
- mp_obj_t t = inject_exc;
+ obj1 = inject_exc;
inject_exc = MP_OBJ_NULL;
- nlr_raise(mp_make_raise_obj(t));
+ obj1 = mp_make_raise_obj(obj1);
+ RAISE(obj1);
}
+
// loop to execute byte code
for (;;) {
dispatch_loop:
@@ -297,7 +306,8 @@ dispatch_loop:
load_check:
if (obj1 == MP_OBJ_NULL) {
local_name_error:
- nlr_raise(mp_obj_new_exception_msg(&mp_type_NameError, "local variable referenced before assignment"));
+ obj1 = mp_obj_new_exception_msg(&mp_type_NameError, "local variable referenced before assignment");
+ RAISE(obj1);
}
PUSH(obj1);
DISPATCH();
@@ -580,7 +590,7 @@ unwind_jump:
// if TOS is an integer, does something else
// else error
if (mp_obj_is_exception_type(TOP())) {
- nlr_raise(sp[-1]);
+ RAISE(sp[-1]);
}
if (TOP() == mp_const_none) {
sp--;
@@ -606,6 +616,7 @@ unwind_jump:
ENTRY(MP_BC_FOR_ITER):
DECODE_ULABEL; // the jump offset if iteration finishes; for labels are always forward
+ save_sp = sp;
obj1 = mp_iternext_allow_raise(TOP());
if (obj1 == MP_OBJ_NULL) {
--sp; // pop the exhausted iterator
@@ -829,12 +840,14 @@ unwind_return:
}
}
if (obj1 == MP_OBJ_NULL) {
- nlr_raise(mp_obj_new_exception_msg(&mp_type_RuntimeError, "No active exception to reraise"));
+ obj1 = mp_obj_new_exception_msg(&mp_type_RuntimeError, "No active exception to reraise");
+ RAISE(obj1);
}
} else {
obj1 = POP();
}
- nlr_raise(mp_make_raise_obj(obj1));
+ obj1 = mp_make_raise_obj(obj1);
+ RAISE(obj1);
ENTRY(MP_BC_YIELD_VALUE):
yield:
@@ -847,7 +860,7 @@ yield:
ENTRY(MP_BC_YIELD_FROM): {
//#define EXC_MATCH(exc, type) MP_OBJ_IS_TYPE(exc, type)
#define EXC_MATCH(exc, type) mp_obj_exception_match(exc, type)
-#define GENERATOR_EXIT_IF_NEEDED(t) if (t != MP_OBJ_NULL && EXC_MATCH(t, &mp_type_GeneratorExit)) { nlr_raise(t); }
+#define GENERATOR_EXIT_IF_NEEDED(t) if (t != MP_OBJ_NULL && EXC_MATCH(t, &mp_type_GeneratorExit)) { RAISE(t); }
mp_vm_return_kind_t ret_kind;
obj1 = POP();
mp_obj_t t_exc = MP_OBJ_NULL;
@@ -890,7 +903,7 @@ yield:
GENERATOR_EXIT_IF_NEEDED(t_exc);
DISPATCH();
} else {
- nlr_raise(obj2);
+ RAISE(obj2);
}
}
}
@@ -912,25 +925,27 @@ yield:
DISPATCH();
ENTRY_DEFAULT:
- printf("code %p, byte code 0x%02x not implemented\n", ip, op);
obj1 = mp_obj_new_exception_msg(&mp_type_NotImplementedError, "byte code not implemented");
nlr_pop();
fastn[0] = obj1;
return MP_VM_RETURN_EXCEPTION;
+
#if !MICROPY_USE_COMPUTED_GOTOS
} // switch
#endif
- }
+ } // for loop
} else {
+exception_handler:
// exception occurred
// check if it's a StopIteration within a for block
if (*save_ip == MP_BC_FOR_ITER && mp_obj_is_subclass_fast(mp_obj_get_type(nlr.ret_val), &mp_type_StopIteration)) {
- ip = save_ip + 1;
+ const byte *ip = save_ip + 1;
+ machine_uint_t unum;
DECODE_ULABEL; // the jump offset if iteration finishes; for labels are always forward
- --sp; // pop the exhausted iterator
- ip += unum; // jump to after for-block
+ *ip_in_out = ip + unum; // jump to after for-block
+ *sp_in_out = save_sp - 1; // pop the exhausted iterator
goto outer_dispatch_loop; // continue with dispatch loop
}
@@ -969,14 +984,15 @@ yield:
currently_in_except_block = 1;
// catch exception and pass to byte code
- sp = MP_TAGPTR_PTR(exc_sp->val_sp);
- ip = exc_sp->handler;
+ *ip_in_out = exc_sp->handler;
+ mp_obj_t *sp = MP_TAGPTR_PTR(exc_sp->val_sp);
// save this exception in the stack so it can be used in a reraise, if needed
exc_sp->prev_exc = nlr.ret_val;
// push(traceback, exc-val, exc-type)
PUSH(mp_const_none);
PUSH(nlr.ret_val);
PUSH(mp_obj_get_type(nlr.ret_val));
+ *sp_in_out = sp;
} else {
// propagate exception to higher level