Re: build warnings

On Fri, Jan 29, 2010 at 08:03:37PM +1100, Michael Wookey wrote:

With current master (dace5dd1), the following build warnings appear on
Ubuntu 9.10 (x86):

  run-command.c: In function ‘notify_parent’:
  run-command.c:70: warning: ignoring return value of ‘write’,
declared with attribute warn_unused_result
  run-command.c: In function ‘die_child’:
  run-command.c:80: warning: ignoring return value of ‘write’,
declared with attribute warn_unused_result
  run-command.c:81: warning: ignoring return value of ‘write’,
declared with attribute warn_unused_result
  run-command.c:82: warning: ignoring return value of ‘write’,
declared with attribute warn_unused_result

There is no point in looking at the return value of any of those calls.
The first one is about notifying the parent process of a child's failure
to exec while it is dying (the surrounding function is even an atexit
handler!). If we can't do that, there is really no alternative behavior.
The latter three are printing fatal error messages. If we fail at that,
there is not much to do (unless we should print an error...).

  ~$ gcc --version
  gcc (Ubuntu 4.4.1-4ubuntu9) 4.4.1

I have heard that Ubuntu recently switched on unused result warnings by
default, and I have seen complaints that it is generating a lot of
uninteresting warnings like these.

Does anybody know if this behavior is here to stay? Can it be worked
around with -Wno-warn-unused-result or something? There are few enough
callsites here that I am not entirely opposed to annotating them with
"(void)write" (does that actually work?), but I worry that this is a
slippery slope. There are a lot of other calls whose return values are
also uninteresting (just looking in the vicinity of this code, I see an
fflush and a close, neither of whose failure would be interesting). I'm
not excited at the prospect of annotating all of them.

-Peff