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dpgeorgedpgeorge
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Merge pull request adafruit#246 from pfalcon/exc_stack_entry
vm: Introduce structure for exception stack entry, record entry type.
2 parents 8b56beb + c9887cb commit 532f2c3

2 files changed

Lines changed: 102 additions & 14 deletions

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‎py/vm.c‎

Lines changed: 31 additions & 14 deletions
Original file line numberDiff line numberDiff line change
@@ -13,8 +13,22 @@
1313
#include "bc0.h"
1414
#include "bc.h"
1515

16-
// (value) stack grows down (to be compatible with native code when passing pointers to the stack), top element is pointed to
17-
// exception stack grows up, top element is pointed to
16+
// Value stack grows up (this makes it incompatible with native C stack, but
17+
// makes sure that arguments to functions are in natural order arg1..argN
18+
// (Python semantics mandates left-to-right evaluation order, including for
19+
// function arguments). Stack pointer is pre-incremented and points at the
20+
// top element.
21+
// Exception stack also grows up, top element is also pointed at.
22+
23+
// Exception stack entry
24+
typedef struct _mp_exc_stack {
25+
const byte *handler;
26+
// bit 0 is saved currently_in_except_block value
27+
machine_uint_t val_sp;
28+
// We might only have 2 interesting cases here: SETUP_EXCEPT & SETUP_FINALLY,
29+
// consider storing it in bit 1 of val_sp. TODO: SETUP_WITH?
30+
byte opcode;
31+
} mp_exc_stack;
1832

1933
#define DECODE_UINT do { unum = *ip++; if (unum > 127) { unum = ((unum & 0x3f) << 8) | (*ip++); } } while (0)
2034
#define DECODE_ULABEL do { unum = (ip[0] | (ip[1] << 8)); ip += 2; } while (0)
@@ -83,8 +97,8 @@ bool mp_execute_byte_code_2(const byte *code_info, const byte **ip_in_out, mp_ob
8397
nlr_buf_t nlr;
8498

8599
volatile machine_uint_t currently_in_except_block = 0; // 0 or 1, to detect nested exceptions
86-
machine_uint_t exc_stack[8]; // on the exception stack we store (ip, sp | X) for each block, X = previous value of currently_in_except_block
87-
machine_uint_t *volatile exc_sp = &exc_stack[0] - 1; // stack grows up, exc_sp points to top of stack
100+
mp_exc_stack exc_stack[4];
101+
mp_exc_stack *volatile exc_sp = &exc_stack[0] - 1; // stack grows up, exc_sp points to top of stack
88102
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)
89103

90104
// outer exception handling loop
@@ -318,9 +332,12 @@ bool mp_execute_byte_code_2(const byte *code_info, const byte **ip_in_out, mp_ob
318332

319333
// matched against: POP_BLOCK or POP_EXCEPT (anything else?)
320334
case MP_BC_SETUP_EXCEPT:
335+
case MP_BC_SETUP_FINALLY:
321336
DECODE_ULABEL; // except labels are always forward
322-
*++exc_sp = (machine_uint_t)ip + unum;
323-
*++exc_sp = (((machine_uint_t)sp) | currently_in_except_block);
337+
++exc_sp;
338+
exc_sp->opcode = op;
339+
exc_sp->handler = ip + unum;
340+
exc_sp->val_sp = (((machine_uint_t)sp) | currently_in_except_block);
324341
currently_in_except_block = 0; // in a try block now
325342
break;
326343

@@ -359,8 +376,8 @@ bool mp_execute_byte_code_2(const byte *code_info, const byte **ip_in_out, mp_ob
359376
case MP_BC_POP_BLOCK:
360377
// we are exiting an exception handler, so pop the last one of the exception-stack
361378
assert(exc_sp >= &exc_stack[0]);
362-
currently_in_except_block = (exc_sp[0] & 1); // restore previous state
363-
exc_sp -= 2; // pop back to previous exception handler
379+
currently_in_except_block = (exc_sp->val_sp & 1); // restore previous state
380+
exc_sp--; // pop back to previous exception handler
364381
break;
365382

366383
// matched against: SETUP_EXCEPT
@@ -371,8 +388,8 @@ bool mp_execute_byte_code_2(const byte *code_info, const byte **ip_in_out, mp_ob
371388
assert(currently_in_except_block);
372389
//sp = (mp_obj_t*)(*exc_sp--);
373390
//exc_sp--; // discard ip
374-
currently_in_except_block = (exc_sp[0] & 1); // restore previous state
375-
exc_sp -= 2; // pop back to previous exception handler
391+
currently_in_except_block = (exc_sp->val_sp & 1); // restore previous state
392+
exc_sp--; // pop back to previous exception handler
376393
//sp -= 3; // pop 3 exception values
377394
break;
378395

@@ -550,17 +567,17 @@ bool mp_execute_byte_code_2(const byte *code_info, const byte **ip_in_out, mp_ob
550567
// at the moment we are just raising the very last exception (the one that caused the nested exception)
551568

552569
// move up to previous exception handler
553-
currently_in_except_block = (exc_sp[0] & 1); // restore previous state
554-
exc_sp -= 2; // pop back to previous exception handler
570+
currently_in_except_block = (exc_sp->val_sp & 1); // restore previous state
571+
exc_sp--; // pop back to previous exception handler
555572
}
556573

557574
if (exc_sp >= &exc_stack[0]) {
558575
// set flag to indicate that we are now handling an exception
559576
currently_in_except_block = 1;
560577

561578
// catch exception and pass to byte code
562-
sp = (mp_obj_t*)(exc_sp[0] & (~((machine_uint_t)1)));
563-
ip = (const byte*)(exc_sp[-1]);
579+
sp = (mp_obj_t*)(exc_sp->val_sp & (~((machine_uint_t)1)));
580+
ip = exc_sp->handler;
564581
// push(traceback, exc-val, exc-type)
565582
PUSH(mp_const_none);
566583
PUSH(nlr.ret_val);

‎tests/basics/try-finally1.py‎

Lines changed: 71 additions & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -0,0 +1,71 @@
1+
print("noexc-finally")
2+
try:
3+
print("try")
4+
finally:
5+
print("finally")
6+
7+
print("noexc-finally-finally")
8+
try:
9+
print("try1")
10+
try:
11+
print("try2")
12+
finally:
13+
print("finally2")
14+
finally:
15+
print("finally1")
16+
print()
17+
18+
print("noexc-finally-func-finally")
19+
def func2():
20+
try:
21+
print("try2")
22+
finally:
23+
print("finally2")
24+
25+
try:
26+
print("try1")
27+
func2()
28+
finally:
29+
print("finally1")
30+
print()
31+
32+
33+
print("exc-finally-except")
34+
try:
35+
print("try1")
36+
try:
37+
print("try2")
38+
foo()
39+
except:
40+
print("except2")
41+
finally:
42+
print("finally1")
43+
print()
44+
45+
print("exc-finally-except-filter")
46+
try:
47+
print("try1")
48+
try:
49+
print("try2")
50+
foo()
51+
except NameError:
52+
print("except2")
53+
finally:
54+
print("finally1")
55+
print()
56+
57+
58+
print("exc-except-finally-finally")
59+
try: # top-level catch-all except to not fail script
60+
try:
61+
print("try1")
62+
try:
63+
print("try2")
64+
foo()
65+
finally:
66+
print("finally2")
67+
finally:
68+
print("finally1")
69+
except:
70+
print("catch-all except")
71+
print()

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