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Forward-port of r52136,52138: a review of overflow-detecting code.

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* unified the way intobject, longobject and mystrtoul handle
  values around -sys.maxint-1.

* in general, trying to entierely avoid overflows in any computation
  involving signed ints or longs is extremely involved.  Fixed a few
  simple cases where a compiler might be too clever (but that's all
  guesswork).

* more overflow checks against bad data in marshal.c.

* 2.5 specific: fixed a number of places that were still confusing int
  and Py_ssize_t.  Some of them could potentially have caused
  "real-world" breakage.

* list.pop(x): fixing overflow issues on x was messy.  I just reverted
  to PyArg_ParseTuple("n"), which does the right thing.  (An obscure
  test was trying to give a Decimal to list.pop()... doesn't make
  sense any more IMHO)

* trying to write a few tests...
This commit is contained in:
Armin Rigo 2006-10-04 12:17:45 +00:00
parent 0d2f498a4c
commit 7ccbca93a2
19 changed files with 186 additions and 106 deletions
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16
Objects/intobject.c
View file

@ -546,6 +546,17 @@ int_mul(PyObject *v, PyObject *w)
}
}
/* Integer overflow checking for unary negation: on a 2's-complement
* box, -x overflows iff x is the most negative long. In this case we
* get -x == x. However, -x is undefined (by C) if x /is/ the most
* negative long (it's a signed overflow case), and some compilers care.
* So we cast x to unsigned long first. However, then other compilers
* warn about applying unary minus to an unsigned operand. Hence the
* weird "0-".
*/
#define UNARY_NEG_WOULD_OVERFLOW(x) \
((x) < 0 && (unsigned long)(x) == 0-(unsigned long)(x))
/* Return type of i_divmod */
enum divmod_result {
DIVMOD_OK, /* Correct result */
@ -565,7 +576,7 @@ i_divmod(register long x, register long y,
return DIVMOD_ERROR;
}
/* (-sys.maxint-1)/-1 is the only overflow case. */
if (y == -1 && x == LONG_MIN)
if (y == -1 && UNARY_NEG_WOULD_OVERFLOW(x))
return DIVMOD_OVERFLOW;
xdivy = x / y;
xmody = x - xdivy * y;
@ -756,7 +767,8 @@ int_neg(PyIntObject *v)
{
register long a;
a = v->ob_ival;
if (a < 0 && (unsigned long)a == 0-(unsigned long)a) {
/* check for overflow */
if (UNARY_NEG_WOULD_OVERFLOW(a)) {
PyObject *o = PyLong_FromLong(a);
if (o != NULL) {
PyObject *result = PyNumber_Negative(o);