Re: [PATCH v4 1/2] man/man3/strto[u]l.3: BUGS: Signed numbers and white space are not rejected

Alejandro Colomar
2025-03-23T17:04:00Z

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On Sun, Mar 23, 2025 at 05:55:50PM +0100, Alejandro Colomar wrote:
> Hi Bruno,
>
> On Sun, Mar 23, 2025 at 04:52:15PM +0100, Bruno Haible wrote:
> > Alejandro Colomar wrote:
> > > Is patch 2/2 also good to you?
> >
> > I couldn't tell without looking at the entire page
> > ("groff -Tutf8 -mandoc strtol.3 | less -R"). But now...
> >
> > > <https://www.alejandro-colomar.es/src/alx/linux/man-pages/man-pages.git/commit/?h=contrib&id=cbcf76d19f864da8c54e41b600ff5661b195b58e>
> >
> > you gave me the information where to look at your work-in-progress tree.
>
> Yup. :)
>
> > Here are my findings on these two pages:
> >
> > * In strtol.3, the example has three mistakes:
> > - Missing semicolon at the end of the second line.
>
> Thanks!
>
> > - If LONG_MIN < min < LONG_MAX, the condition (errno == ERANGE && n == min)
> > will never be true.
> > If LONG_MIN < max < LONG_MAX, the condition (errno == ERANGE && n == max)
> > will never be true.
>
> D'oh! I'm too used to strtoi(3bsd) that I make these mistakes when
> switching to strtol(3).
>
> > - It does not distinguish success with value 0 from failure due to
> > no digits. (This matters when min <= 0 <= max.) Since errno is not
> > guaranteed to be set in this case, the caller needs to look at *endptr.
> > The example thus becomes:
>
> Yeah, I wanted to isolate the range checking from the rest. Maybe I
> should just put this in that sample code?:
>
> if ((errno == ERANGE && n == LONG_MIN) || n < min)
> goto too_low;
> if ((errno == ERANGE && n == LONG_MAX) || n > max)
> goto too_high;
>
> Without having the strtol(3) call at all?
>
> >
> > char *end;
> > errno = 0;
> > n = strtol(s, &end, base);
> > if (end == s)
> > goto no_number;
> > if ((errno == ERANGE && n == LONG_MIN) || n < min)
> > goto too_low;
> > if ((errno == ERANGE && n == LONG_MAX) || n > max)
> > goto too_high;
>

I ended up doing what you said:

<https://www.alejandro-colomar.es/src/alx/linux/man-pages/man-pages.git/commit/?h=contrib&id=ebe5a89dcd431d15c54ebc22eaa35721496fee4b>

> On the other hand, I should put this in the EXAMPLES section, to have
> a full example.
>
> >
> > * strtol.3 and strtoul.3 mention
> > "If base is zero or 16, the string may then include a "0x" or "0X" prefix,
> > and the number will be read in base 16"
> > They should also mention:
> > "If base is zero or 2, the string may then include a "0b" or "0B" prefix,
> > and the number will be read in base 2"
>
> Yep, I need to update many pages for C23. I'll do this update for this
> page now.
>
> Thanks!
>
>
> Cheers,
> Alex
>
> > References:
> > - ISO C 23 § 7.24.1.7.(3)
> > - https://sourceware.org/git/?p=glibc.git;a=commitdiff;h=64924422a99690d147a166b4de3103f3bf3eaf6c
> >
> > Bruno
> >
> >
> >
> >
>
> --
> <https://www.alejandro-colomar.es/>

--
<https://www.alejandro-colomar.es/>