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. -- Richard Smith