Re: Bug in gets function?

[Rich Felker <dalias@libc.org>]

On Mon, Feb 11, 2019 at 06:55:24PM -0800, Keyhan Vakil wrote:
> Hi. It seems that the gets function does not follow the C99 spec. In
> particular, if the input contains a null byte in the middle of the
> input, then the new-line character is not discarded.
> 
> For reference, here's the relevant part in the C99 standard
> (7.19.7.7):
> 
> > The gets function reads characters from the input stream pointed to
> > by stdin, into the array pointed to by s, until end-of-file is
> > encountered or a new-line character is read. Any new-line character
> > is discarded, and a null character is written immediately after the
> > last character read into the array.
> 
> Here is an example:
> 
>     #include <stdio.h>
>     char s[8];
>     int main() {
>         gets(s);
>         for (int i = 0; i < sizeof s; i++) {
>             printf("%02x ", s[i]);
>         }
>         printf("\n");
>         return 0;
>     }
> 
> When compiled against gcc:
> 
>     $ echo -e 'A\x00B' | ./a.out
>     41 00 42 00 00 00 00 00
> 
> When compiled against musl:
> 
>     $ echo -e 'A\x00B' | ./a.out
>     41 00 42 0a 00 00 00 00
> 
> Note the terminating newline, which contradicts the spec.

I think this bug report is correct; however the gets function is
awful, removed in C11, and should never be used. :-)

I will see what can be done to fix it though.

Rich