Re: [PATCH] atoi.3: Explain disadvantages of atoi()

["Michael Kerrisk (man-pages)" <mtk.manpages@gmail.com>]

Hello Arkadiusz,

On 6/18/20 10:42 PM, Arkadiusz Drabczyk wrote:
> I believe new users should be discouraged from using atoi() and that
> its disadvantages should be explained.
> 
> I added the information that 0 is returned on error - although C
> standard and POSIX say that "If the value of the result cannot be
> represented, the behavior is undefined." there are some
> interpretations that 0 has to be returned
> https://stackoverflow.com/questions/38393162/what-can-i-assume-about-the-behaviour-of-atoi-on-error
> and this is also what happens in practice with glibc, musl and uClibc.
> 
> Signed-off-by: Arkadiusz Drabczyk <arkadiusz@drabczyk.org>

Thanks. Patch applied. I also made a few small tweaks. The 
results have been pushed to master.

Thanks,

Michael

> ---
>  man3/atoi.3 | 13 ++++++++++++-
>  1 file changed, 12 insertions(+), 1 deletion(-)
> 
> diff --git a/man3/atoi.3 b/man3/atoi.3
> index c5894d3..3c6527a 100644
> --- a/man3/atoi.3
> +++ b/man3/atoi.3
> @@ -81,7 +81,18 @@ functions behave the same as
>  except that they convert the initial portion of the
>  string to their return type of \fIlong\fP or \fIlong long\fP.
>  .SH RETURN VALUE
> -The converted value.
> +The converted value or 0 on error.
> +.SH BUGS
> +.I errno
> +is not set on error so there is no way to distinguish between 0 as an
> +error and as the converted value.
> +No checks for overflow or underflow are done.
> +Only input in decimal base can be converted.
> +It's recommended to use
> +.BR strtol ()
> +and
> +.BR strtoul ()
> +family of functions in new programs.
>  .SH ATTRIBUTES
>  For an explanation of the terms used in this section, see
>  .BR attributes (7).
> 


-- 
Michael Kerrisk
Linux man-pages maintainer; http://www.kernel.org/doc/man-pages/
Linux/UNIX System Programming Training: http://man7.org/training/