On 16/01/2019 14:31, Heiko Schlittermann via Exim-users wrote:
Mike Tubby via Exim-users <[email protected]> (Mi 16 Jan 2019 14:58:07 CET):
All,
When compiling Exim 4.91 on Ubuntu 16.04.5 LTS I get a gcc warning in the
USR1 signal handler:
gcc exim.c
exim.c: In function ‘usr1_handler’:
exim.c:242:1: warning: ignoring return value of ‘write’, declared with
attribute warn_unused_result [-Wunused-result]
(void)write(fd, process_info, process_info_len);
^
gcc expand.c
On a curent Debian this attribute isn't used for the write(2)
call. Hm. Intentional?
if (fd > 0) {
ssize_t x;
int y;
x = write(fd, process_info, process_info_len);
y = close(fd);
}
242,243d252
< (void)write(fd, process_info, process_info_len);
< (void)close(fd);
While (void) write(…) seems to express clearly the intention,
I'm not sure why GCC does not understand it (anymore, not yet?)
Heiko, I completely agree with the intention of:
(void)function(...)
and have used it many times myself over the years - I can only guess
that the makefile with GCC 5.4.0 options turns back on something that
makes this a warning again.
Here's the GCC version:
root@relay1:~/exim-4.91# gcc --version
gcc (Ubuntu 5.4.0-6ubuntu1~16.04.11) 5.4.0 20160609
Copyright (C) 2015 Free Software Foundation, Inc.
This is free software; see the source for copying conditions. There is NO
warranty; not even for MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
Beside from your proposal using a dummy variable, I found another
way
if (write(…));
if (close(…));
But it needs a comment or a macro like
#define IGNORE_RESULT(x) if(x)
…
IGNORE_RESULT(write(…))
Agreed but this is getting even more messy ;-)
Regards
Mike
--
Heiko
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