diff options
Diffstat (limited to 'Python/mystrtoul.c')
| -rw-r--r-- | Python/mystrtoul.c | 30 |
1 files changed, 21 insertions, 9 deletions
diff --git a/Python/mystrtoul.c b/Python/mystrtoul.c index 51553fbe1f..0dda4be2ee 100644 --- a/Python/mystrtoul.c +++ b/Python/mystrtoul.c @@ -195,10 +195,19 @@ overflowed: return (unsigned long)-1; } +/* Checking for overflow in PyOS_strtol is a PITA since C doesn't define + * anything about what happens when a signed integer operation overflows, + * and some compilers think they're doing you a favor by being "clever" + * then. Python assumes a 2's-complement representation, so that the bit + * pattern for the largest postive signed long is LONG_MAX, and for + * the smallest negative signed long is LONG_MAX + 1. + */ + long PyOS_strtol(char *str, char **ptr, int base) { long result; + unsigned long uresult; char sign; while (*str && isspace(Py_CHARMASK(*str))) @@ -208,17 +217,20 @@ PyOS_strtol(char *str, char **ptr, int base) if (sign == '+' || sign == '-') str++; - result = (long) PyOS_strtoul(str, ptr, base); + uresult = PyOS_strtoul(str, ptr, base); - /* Signal overflow if the result appears negative, - except for the largest negative integer */ - if (result < 0 && !(sign == '-' && result == -result)) { + if (uresult <= (unsigned long)LONG_MAX) { + result = (long)uresult; + if (sign == '-') + result = -result; + } + else if (sign == '-' && uresult == (unsigned long)LONG_MAX + 1) { + assert(LONG_MIN == -LONG_MAX-1); + result = LONG_MIN; + } + else { errno = ERANGE; - result = 0x7fffffff; + result = LONG_MAX; } - - if (sign == '-') - result = -result; - return result; } |