Re: Strange interval arithmetic

On Wed, Nov 30, 2005 at 05:20:54PM -0500, Tom Lane wrote:
> Michael Fuhr <mike(at)fuhr(dot)org> writes:
> > I'm looking at all the strtol() calls in datetime.c right now; I
> > haven't looked anywhere else yet. Should I bother checking values
> > that will be range checked later anyway? Time zone displacements,
> > for example?
>
> Good question. Is strtol guaranteed to return INT_MAX or INT_MIN on
> overflow, or might it return the overflowed value?

The Open Group Base Specifications say this:

Upon successful completion, these functions shall return the converted
value, if any. If no conversion could be performed, 0 shall be
returned and errno may be set to [EINVAL].

If the correct value is outside the range of representable values,
{LONG_MIN}, {LONG_MAX}, {LLONG_MIN}, or {LLONG_MAX} shall be returned
(according to the sign of the value), and errno set to [ERANGE].

http://www.opengroup.org/onlinepubs/009695399/functions/strtol.html

FreeBSD and Solaris both peg overflow at LONG_MAX, and that behavior
is what I noticed in the first place. I don't know if any systems
behave otherwise. Alvaro suggested checking for both LONG_MAX and
ERANGE; I suppose if we check for LONG_MAX then we should also check
for LONG_MIN. I don't know if any systems might set ERANGE in a
non-error situation.

--
Michael Fuhr