Message256143
The peephole optimizer computes 2**(2**100), but if I press CTRL+c (the result will probably kills my memory anyway), I get an assertion error (with a Python compiled in debug mode).
$ ./python
>>> 2**(2**100)
^C
python: Python/ceval.c:1218: PyEval_EvalFrameEx: Assertion `!PyErr_Occurred()' failed.
Abandon (core dumped)
fold_binops_on_constants() returns 0 with an exception (KeyboardInterrupt) raised. The problem is in the caller which doesn't handle the exception properly:
if (h >= 0 &&
ISBASICBLOCK(blocks, h, i-h+1) &&
fold_binops_on_constants(&codestr[i], consts, CONST_STACK_LASTN(2))) {
i -= 2;
memset(&codestr[h], NOP, i - h);
assert(codestr[i] == LOAD_CONST);
CONST_STACK_POP(2);
CONST_STACK_PUSH_OP(i);
}
There is probably the same error on fold_unaryops_on_constants().
Python 2.7 looks to behave correctly:
$ python2.7
>>> 2**(2**100)
^C
Traceback (most recent call last):
File "<stdin>", line 1, in <module>
KeyboardInterrupt
But in fact Python 2.7 is much worse :-D Peephole optimizer of Python 2.7 clears *all* exceptions (!) and it only optimizes 2**100, but not 2**(2**100). That's why the bug is not easily reproduced on Python 2.7. fold_binops_on_constants():
if (newconst == NULL) {
if(!PyErr_ExceptionMatches(PyExc_KeyboardInterrupt))
PyErr_Clear();
return 0;
} |
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Date |
User |
Action |
Args |
2015-12-09 08:03:24 | vstinner | set | recipients:
+ vstinner |
2015-12-09 08:03:24 | vstinner | set | messageid: <1449648204.19.0.769728792688.issue25828@psf.upfronthosting.co.za> |
2015-12-09 08:03:24 | vstinner | link | issue25828 messages |
2015-12-09 08:03:23 | vstinner | create | |
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