id	summary	reporter	owner	description	type	status	milestone	component	version	severity	resolution	keywords	cc
2534	Removing gcc warning	richard@…	chris_kohlhoff	"The function

  boost::asio::detail::pipe_select_interrupter::interupt()

in <boost/asio/detail/pipe_select_interrupter.hpp> produces the following warning in gcc 4.3.2 / glibc 2.8 when compiled with -O1 or higher.  The warning occurs even without any -W options.

  ./boost/asio/detail/pipe_select_interrupter.hpp:75:
    warning: ignoring return value of ‘ssize_t write(int,
    const void*, size_t)’, declared with attribute
    warn_unused_result

As the message implies, gcc issues this warning whenever a function declared with __attribute__((warn_unused_result)); it appears that gcc implicitly places this attribute on ::write as the glibc header doesn't contain it.
A short test case is:

  #include <unistd.h>
  int main() { ::write(1, 0, 0); }

To suppress the warning, the function interupt() function can be altered as follows:

  #include <boost/concept_check.hpp>

  void interrupt()
  {
    char byte = 0;
    ignore_unused_variable_warning( ::write(write_descriptor_, &byte, 1) );
  }

Is there any chance of making a change along these lines?

Apologies if this is a know issue: a quick search of the mailing list didn't turn anything up.

"	Bugs	closed	Boost 1.38.0	asio	Boost 1.37.0	Cosmetic	fixed	gcc warning