[Bug c/66425] (void) cast doesn't suppress __attribute__((warn_unused_result))

["romato.san1337 at gmail dot com" <gcc-bugzilla@gcc.gnu.org>]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=66425

Roman Krotov <romato.san1337 at gmail dot com> changed:

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                 CC|                            |romato.san1337 at gmail dot com

--- Comment #54 from Roman Krotov <romato.san1337 at gmail dot com> ---
I'm also very frustrated about this behavior, but I'm not asking to **change**
it. I see your point and, although I think it's severely outdated now, I
respect your decision.

Instead I'm offering a compromise, or to better describe it, a win-win
solution.
What about introducing something like `-Wno-void-unused`, which would only
disable the warnings for the (void) casted calls?

And I'm not asking to do it for me, or some other random dudes; do it for
systemd, they are also very frustrated about this:
https://github.com/systemd/systemd/blob/5a96b32dead5132ba37a8b968c59101c2aac8d23/meson.build#L400

That's because they use (void) casts very frequently:
https://github.com/search?q=repo%3Asystemd%2Fsystemd+language%3AC+%22%28void%29%22&type=code

You can probably say they are in the wrong by doing the bad practice and should
do a macro instead.
And you may be right. I really appreciate your commitment to teach people good
practices, but **suggesting** them (by setting the default behavior which
**recommends** the programmers to use these practices) should be enough.
I don't think it's a good idea to **force** people to use them, by either
spamming them with warnings (useless to them, because they already made a
decision) or making them disable such warnings altogether, which could lead
them to miss a bug where they forgot to use a value of a function (which they
didn't cast with void).

You may say it's their fault, but let me ask you a question, who is winning
from the current situation? Certainly, not you, because you didn't convince
them to change, instead you just made them not listen to you, see also
julia-language and mpv:
https://github.com/search?q=%22-Wno-unused-result%22&type=code

And certainly, not them, because of the bug-risk I typed above, which is really
unfortunate for such a big and widely-used project as systemd.
Also, making them switch to clang (or drop gcc support) would be really bad,
because nothing hurts FOSS and frustrates me in a project more than a
permissive license. Eww..

Sorry, if I was a little bit harsh there, I really appreciate your contribution
to FOSS and Linux development, and I would never switch to clang.
Just, please note, that, again, I'm begging you to just implement a non-default
switch that would make everyone's lives easier.

Why "everyone's"? You see,

If a new programmer encounters this "problem", they would think it's just a
"gcc bug", because "clang works as expected" (and also the mentioned projects
wrote like this in a comment), so they just disable the warnings altogether.
Nobody won, especially the programmer.
Now consider the situation where you implemented the switch, but wrote, for
example, in the manpage just that "It's not recommended". Now they will be
curious why, so they will try to find an answer, and the search will probably
lead them to the gnu.org page which has the answer.

See, how even though you might think you gave the ability to write a bad code,
in reality you would give the exact point why not to use (void)? (Which they
really need because other compilers/linters are trying to convince them
otherwise.)
Come on, at least please admit that the situation described above would still
be better than today's.

If you will find at least some of my points somewhat reasonable, please share
my comment with the people that can help bring this improvement to life.