[Python-Dev] 're' crashes ? (original) (raw)

Thomas Wouters thomas@xs4all.net
Sat, 12 Aug 2000 21:45:24 +0200

I'm not trying to sound like Eric (though I don't mind if I do ;) but my Python crashes. Or rather, test_re fails with a coredump, since this afternoon or so. I'm fairly certain it was working fine yesterday, and it's an almost-vanilla CVS tree (I was about to check-in the fixes to Tools/compiler, and tried to use the compiler on the std lib and the test suite, when I noticed the coredump.)

The coredump says this:

#0 eval_code2 (co=0x824ba50, globals=0x82239b4, locals=0x0, args=0x827e18c, argcount=2, kws=0x827e194, kwcount=0, defs=0x82211c0, defcount=1, owner=0x0) at ceval.c:1474 1474 Py_DECREF(w);

Which is part of the FOR_LOOP opcode:

1461 case FOR_LOOP: 1462 /* for v in s: ... 1463 On entry: stack contains s, i. 1464 On exit: stack contains s, i+1, s[i]; 1465 but if loop exhausted: 1466 s, i are popped, and we jump / 1467 w = POP(); / Loop index / 1468 v = POP(); / Sequence object / 1469 u = loop_subscript(v, w); 1470 if (u != NULL) { 1471 PUSH(v); 1472 x = PyInt_FromLong(PyInt_AsLong(w)+1); 1473 PUSH(x); 1474 Py_DECREF(w); 1475 PUSH(u); 1476 if (x != NULL) continue; 1477 } 1478 else { 1479 Py_DECREF(v); 1480 Py_DECREF(w); 1481 / A NULL can mean "s exhausted" 1482 but also an error: */ 1483 if (PyErr_Occurred()) 1484 why = WHY_EXCEPTION;

I think this isn't caused by this code, but rather by a refcounting bug somewhere. 'w' should be an int, and it's used on line 1472, and doesn't cause an error there (unless passing a NULL pointer to PyInt_AsLong() isn't an error ?) But it's NULL at line 1474. Is there an easy way to track an error like this ? Otherwise I'll play around a bit using breakpoints and such in gdb.

-- Thomas Wouters <thomas@xs4all.net>

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