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,