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bpo-42645: Make sure that return/break/continue are only traced once when exiting via a finally block. #23780

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Merged
merged 3 commits into from
Dec 16, 2020
Merged

bpo-42645: Make sure that return/break/continue are only traced once when exiting via a finally block. #23780

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20d6e80
Make sure that return/break/continue are only traced once when exitin…
markshannon Dec 15, 2020
77a4582
Add test for return in try-finally.
markshannon Dec 15, 2020
958f587
Update importlib
markshannon Dec 16, 2020
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16 changes: 4 additions & 12 deletions Lib/test/test_dis.py
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Original file line number Diff line number Diff line change
Expand Up @@ -366,16 +366,12 @@ def _tryfinallyconst(b):
%3d 6 LOAD_FAST 1 (b)
8 CALL_FUNCTION 0
10 POP_TOP

%3d 12 RETURN_VALUE

%3d >> 14 LOAD_FAST 1 (b)
12 RETURN_VALUE
>> 14 LOAD_FAST 1 (b)
16 CALL_FUNCTION 0
18 POP_TOP
20 RERAISE
""" % (_tryfinally.__code__.co_firstlineno + 1,
_tryfinally.__code__.co_firstlineno + 2,
_tryfinally.__code__.co_firstlineno + 4,
_tryfinally.__code__.co_firstlineno + 2,
_tryfinally.__code__.co_firstlineno + 4,
)
Expand All @@ -388,17 +384,13 @@ def _tryfinallyconst(b):
%3d 4 LOAD_FAST 0 (b)
6 CALL_FUNCTION 0
8 POP_TOP

%3d 10 LOAD_CONST 1 (1)
10 LOAD_CONST 1 (1)
12 RETURN_VALUE

%3d >> 14 LOAD_FAST 0 (b)
>> 14 LOAD_FAST 0 (b)
16 CALL_FUNCTION 0
18 POP_TOP
20 RERAISE
""" % (_tryfinallyconst.__code__.co_firstlineno + 1,
_tryfinallyconst.__code__.co_firstlineno + 2,
_tryfinallyconst.__code__.co_firstlineno + 4,
_tryfinallyconst.__code__.co_firstlineno + 2,
_tryfinallyconst.__code__.co_firstlineno + 4,
)
Expand Down
113 changes: 113 additions & 0 deletions Lib/test/test_sys_settrace.py
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Original file line number Diff line number Diff line change
Expand Up @@ -678,6 +678,119 @@ def func():
(4, 'line'),
(4, 'return')])

def test_if_break(self):

def func():
seq = [1, 0]
while seq:
n = seq.pop()
if n:
break # line 5
else:
n = 99
return n # line 8

self.run_and_compare(func,
[(0, 'call'),
(1, 'line'),
(2, 'line'),
(3, 'line'),
(4, 'line'),
(2, 'line'),
(3, 'line'),
(4, 'line'),
(5, 'line'),
(8, 'line'),
(8, 'return')])

def test_break_through_finally(self):

def func():
a, c, d, i = 1, 1, 1, 99
try:
for i in range(3):
try:
a = 5
if i > 0:
break # line 7
a = 8
finally:
c = 10
except:
d = 12 # line 12
assert a == 5 and c == 10 and d == 1 # line 13

self.run_and_compare(func,
[(0, 'call'),
(1, 'line'),
(2, 'line'),
(3, 'line'),
(4, 'line'),
(5, 'line'),
(6, 'line'),
(8, 'line'),
(10, 'line'),
(3, 'line'),
(4, 'line'),
(5, 'line'),
(6, 'line'),
(7, 'line'),
(10, 'line'),
(13, 'line'),
(13, 'return')])

def test_continue_through_finally(self):

def func():
a, b, c, d, i = 1, 1, 1, 1, 99
try:
for i in range(2):
try:
a = 5
if i > 0:
continue # line 7
b = 8
finally:
c = 10
except:
d = 12 # line 12
assert (a, b, c, d) == (5, 8, 10, 1) # line 13

self.run_and_compare(func,
[(0, 'call'),
(1, 'line'),
(2, 'line'),
(3, 'line'),
(4, 'line'),
(5, 'line'),
(6, 'line'),
(8, 'line'),
(10, 'line'),
(3, 'line'),
(4, 'line'),
(5, 'line'),
(6, 'line'),
(7, 'line'),
(10, 'line'),
(3, 'line'),
(13, 'line'),
(13, 'return')])

def test_return_through_finally(self):

def func():
try:
return 2
finally:
4

self.run_and_compare(func,
[(0, 'call'),
(1, 'line'),
(2, 'line'),
(4, 'line'),
(4, 'return')])


class SkipLineEventsTraceTestCase(TraceTestCase):
"""Repeat the trace tests, but with per-line events skipped"""
Expand Down
17 changes: 13 additions & 4 deletions Python/compile.c
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Original file line number Diff line number Diff line change
Expand Up @@ -1695,19 +1695,22 @@ compiler_unwind_fblock(struct compiler *c, struct fblockinfo *info,
return 1;

case FINALLY_TRY:
/* This POP_BLOCK gets the line number of the unwinding statement */
ADDOP(c, POP_BLOCK);
if (preserve_tos) {
if (!compiler_push_fblock(c, POP_VALUE, NULL, NULL, NULL)) {
return 0;
}
}
/* Emit the finally block, restoring the line number when done */
int saved_lineno = c->u->u_lineno;
/* Emit the finally block */
VISIT_SEQ(c, stmt, info->fb_datum);
c->u->u_lineno = saved_lineno;
if (preserve_tos) {
compiler_pop_fblock(c, POP_VALUE, NULL);
}
/* The finally block should appear to execute after the
* statement causing the unwinding, so make the unwinding
* instruction artificial */
c->u->u_lineno = -1;
return 1;

case FINALLY_END:
Expand Down Expand Up @@ -2859,14 +2862,20 @@ compiler_return(struct compiler *c, stmt_ty s)
}
if (preserve_tos) {
VISIT(c, expr, s->v.Return.value);
} else {
/* Emit instruction with line number for expression */
if (s->v.Return.value != NULL) {
SET_LOC(c, s->v.Return.value);
ADDOP(c, NOP);
}
}
if (!compiler_unwind_fblock_stack(c, preserve_tos, NULL))
return 0;
if (s->v.Return.value == NULL) {
ADDOP_LOAD_CONST(c, Py_None);
}
else if (!preserve_tos) {
VISIT(c, expr, s->v.Return.value);
ADDOP_LOAD_CONST(c, s->v.Return.value->v.Constant.value);
}
ADDOP(c, RETURN_VALUE);
NEXT_BLOCK(c);
Expand Down
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