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Date: Mon, 11 Feb 2019 22:48:38 -0500
From: Rich Felker <dalias@...c.org>
To: musl@...ts.openwall.com
Subject: Re: Bug in gets function?
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
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