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Issue #14700: Fix buggy overflow checks for large precision and width in new-style and old-style formatting.

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This commit is contained in:
Mark Dickinson 2012-10-28 10:00:46 +00:00
parent 08114d40e9
commit 75d3600466
7 changed files with 74 additions and 22 deletions
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15
Objects/stringlib/string_format.h
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@ -197,7 +197,6 @@ get_integer(const SubString *str)
{
Py_ssize_t accumulator = 0;
Py_ssize_t digitval;
Py_ssize_t oldaccumulator;
STRINGLIB_CHAR *p;
/* empty string is an error */
@ -209,19 +208,17 @@ get_integer(const SubString *str)
if (digitval < 0)
return -1;
/*
This trick was copied from old Unicode format code. It's cute,
but would really suck on an old machine with a slow divide
implementation. Fortunately, in the normal case we do not
expect too many digits.
Detect possible overflow before it happens:
accumulator * 10 + digitval > PY_SSIZE_T_MAX if and only if
accumulator > (PY_SSIZE_T_MAX - digitval) / 10.
*/
oldaccumulator = accumulator;
accumulator *= 10;
if ((accumulator+10)/10 != oldaccumulator+1) {
if (accumulator > (PY_SSIZE_T_MAX - digitval) / 10) {
PyErr_Format(PyExc_ValueError,
"Too many decimal digits in format string");
return -1;
}
accumulator += digitval;
accumulator = accumulator * 10 + digitval;
}
return accumulator;
}