Re: Is it OK to have compile warnings
Gert Wollny <gw.fossdev@gmail.com> writes:
>> To directly answer your question, since I think everyone so far has told
>> you that you should fix it, this answer from S/O [1]
>>
> [...]
>> [1]
>> http://stackoverflow.com/questions/3614691/casting-to-void-doesnt-remove-warn-unused-result-error/3615000#3615000
> One should note that the question on S/O was about opening "/dev/null"
> which is unlikely to fail.
Less unlikely than one might think. I've seen this fail in several
situations, usually because the program is being run in a partial chroot,
but on one occasion because someone deleted the device. In the latter
case, /dev/null later became a regular file because some program was
opening it with O_CREAT (aie), and that caused all sorts of truly bizarre
problems.
It's sometimes the case that errors really don't need checking, but more
rarely than people think. Good software needs error handling mechanisms
for unusual failure conditions. If you really think that this should
never fail, check the return status with assert(). That way, if the
impossible happens, at least you terminate the process rather than
continuing under false assumptions.
The only exception I've run into for this particular warning in my own
code was in monitoring software that was speaking the IMAP protocol. It
sent a "tag logout" command to the server before closing the socket, but
it truly, absolutely did not care if that write failed, since the correct
action to take if the write failed was to... close the socket. Sending
the logout command was just being polite to the server. In that case, I
used the following construct:
/* Only for clean shutdown, don't care about failure. */
if (socket_write(sd, "tag logout\r\n", 12) < 0) {}
socket_close(sd);
which gcc is happy with. (The socket_* calls are, on Linux, just macros
that expand to write and close. They exist for compatibility with
Windows, where different functions have to be used when working with
sockets.)
--
Russ Allbery (rra@debian.org) <http://www.eyrie.org/~eagle/>
Reply to: