Issue 0006: How does strtoul behave when presented with a subject sequence that begins with a minus sign?

This issue has been automatically converted from the original issue lists and some formatting may not have been preserved.

Authors: Walter J. Murray, WG14
Date: 1992-12-10
Reference document: X3J11/90-020
Submitted against: C90
Status: Closed
Converted from: dr.htm, dr_006.html

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"

Comment from WG14 on 1997-09-23:

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