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Patch for bug #659709: bogus computation of float length

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Python 2.2.x backport candidate. (This bug has been around since
Python 1.6.)
This commit is contained in:
Marc-André Lemburg 2002-12-29 19:44:06 +00:00
parent bbfb910416
commit 79f57833f3
4 changed files with 88 additions and 16 deletions
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31
Objects/unicodeobject.c
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@ -5999,20 +5999,31 @@ formatfloat(Py_UNICODE *buf,
prec = 6;
if (type == 'f' && (fabs(x) / 1e25) >= 1e25)
type = 'g';
PyOS_snprintf(fmt, sizeof(fmt), "%%%s.%d%c",
(flags & F_ALT) ? "#" : "", prec, type);
/* worst case length calc to ensure no buffer overrun:
fmt = %#.<prec>g
buf = '-' + [0-9]*prec + '.' + 'e+' + (longest exp
for any double rep.)
len = 1 + prec + 1 + 2 + 5 = 9 + prec
/* Worst case length calc to ensure no buffer overrun:
'g' formats:
fmt = %#.<prec>g
buf = '-' + [0-9]*prec + '.' + 'e+' + (longest exp
for any double rep.)
len = 1 + prec + 1 + 2 + 5 = 9 + prec
'f' formats:
buf = '-' + [0-9]*x + '.' + [0-9]*prec (with x < 50)
len = 1 + 50 + 1 + prec = 52 + prec
If prec=0 the effective precision is 1 (the leading digit is
always given), therefore increase by one to 10+prec. */
if (buflen <= (size_t)10 + (size_t)prec) {
always given), therefore increase the length by one.
*/
if ((type == 'g' && buflen <= (size_t)10 + (size_t)prec) ||
(type == 'f' && buflen <= (size_t)53 + (size_t)prec)) {
PyErr_SetString(PyExc_OverflowError,
"formatted float is too long (precision too long?)");
"formatted float is too long (precision too large?)");
return -1;
}
PyOS_snprintf(fmt, sizeof(fmt), "%%%s.%d%c",
(flags&F_ALT) ? "#" : "",
prec, type);
return usprintf(buf, fmt, x);
}