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long_format(), long_lshift(): Someone on c.l.py is trying to boost 

SHIFT and MASK, and widen digit.  One problem is that code of the form

    digit << small_integer

implicitly assumes that the result fits in an int or unsigned int
(platform-dependent, but "int sized" in any case), since digit is
promoted "just" to int or unsigned via the usual integer promotions.
But if digit is typedef'ed as unsigned int, this loses information.
The cure for this is just to cast digit to twodigits first.
This commit is contained in:
Tim Peters 2002-08-20 19:00:22 +00:00
parent 76afbd9aa4
commit 0d2d87d202
1 changed files with 2 additions and 2 deletions
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4
Objects/longobject.c
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@ -949,7 +949,7 @@ long_format(PyObject *aa, int base, int addL)
++basebits;
for (i = 0; i < size_a; ++i) {
accum |= a->ob_digit[i] << accumbits;
accum |= (twodigits)a->ob_digit[i] << accumbits;
accumbits += SHIFT;
assert(accumbits >= basebits);
do {
@ -2345,7 +2345,7 @@ long_lshift(PyObject *v, PyObject *w)
z->ob_digit[i] = 0;
accum = 0;
for (i = wordshift, j = 0; j < oldsize; i++, j++) {
accum |= a->ob_digit[j] << remshift;
accum |= (twodigits)a->ob_digit[j] << remshift;
z->ob_digit[i] = (digit)(accum & MASK);
accum >>= SHIFT;
}