Defect Report #006
Submission Date: 10 Dec 92
Submittor: WG14
Source: X3J11/90-020 (Walter J. Murray)
Question 1 It is unclear how the strtoul
function behaves when presented with a subject sequence that begins with
a minus sign. The strtoul function is described in
subclause 7.10.1.6, which contains the following statements.
If the
subject sequence begins with a minus sign, the value resulting from the
conversion is negated.
If the correct value is outside the range of
representable values,
ULONG_MAX is returned, and the value of the macro
ERANGE is stored in errno.
Assume a
typical 32-bit, two's-complement machine with the following limits.
LONG_MIN -2147483648
LONG_MAX 2147483647
ULONG_MAX 4294967295
Assuming that the value of base is zero,
how should strto ul behave (return value and possible
setting of errno) when present ed with the following
sequences? Case 1: "-2147483647" Case 2: "-2147483648"
Case 3: "-2147483649"
Response
The relevant citations are the ones supplied by
you from subclause 7.10.1.6: If the subject sequence begins with a
minus sign, the value resulting from the conversion is negated. If the
correct value is outside the range of representable values,
ULONG_MAX is returned, and the value of the macro
ERANGE is stored in errno. The Committee
believes that there is only one sensible interpretation of a subject
sequence with a minus sign: If the subject sequence (neglecting the
possible minus sign) is outside the range [0, ULONG_MAX],
then the range error is reported. Otherwise, the value is negated(as an
unsigned long int). The answers to your numeric
questions are:
Case 1: 2,147,483,649
Case 2: 2,147,483,648
Case 3: 2,147,483,647
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