Boost C++ Libraries: Ticket #2534: Removing gcc warning

severity changed; keywords set

peter _dot_ schneider _dot_ 127 _at_ googlemail _dot_ com — Tue, 09 Dec 2008 00:45:56 GMT

keywords gcc warning added
severity Problem → Cosmetic

"confirm" bjam-output of my project:

...patience...
...found 1105 targets...
...updating 3 targets...
gcc.compile.c++ bin/gcc-4.3.2/release/serialsap.o
In file included from /usr/local/include/boost-1_37/boost/asio/detail/select_interrupter.hpp:24,
                 from /usr/local/include/boost-1_37/boost/asio/detail/epoll_reactor.hpp:42,
                 from /usr/local/include/boost-1_37/boost/asio/impl/io_service.ipp:25,
                 from /usr/local/include/boost-1_37/boost/asio/io_service.hpp:550,
                 from /usr/local/include/boost-1_37/boost/asio/basic_io_object.hpp:20,
                 from /usr/local/include/boost-1_37/boost/asio/basic_socket.hpp:24,
                 from /usr/local/include/boost-1_37/boost/asio/basic_datagram_socket.hpp:25,
                 from /usr/local/include/boost-1_37/boost/asio.hpp:20,
                 from serialsap.h:8,
                 from serialsap.cpp:1:
/usr/local/include/boost-1_37/boost/asio/detail/eventfd_select_interrupter.hpp: In member function ‘void boost::asio::detail::eventfd_select_interrupter::interrupt()’:
/usr/local/include/boost-1_37/boost/asio/detail/eventfd_select_interrupter.hpp:89: warning: ignoring return value of ‘ssize_t write(int, const void*, size_t)’, declared with attribute warn_unused_result
In file included from /usr/local/include/boost-1_37/boost/asio/detail/select_interrupter.hpp:25,
                 from /usr/local/include/boost-1_37/boost/asio/detail/epoll_reactor.hpp:42,
                 from /usr/local/include/boost-1_37/boost/asio/impl/io_service.ipp:25,
                 from /usr/local/include/boost-1_37/boost/asio/io_service.hpp:550,
                 from /usr/local/include/boost-1_37/boost/asio/basic_io_object.hpp:20,
                 from /usr/local/include/boost-1_37/boost/asio/basic_socket.hpp:24,
                 from /usr/local/include/boost-1_37/boost/asio/basic_datagram_socket.hpp:25,
                 from /usr/local/include/boost-1_37/boost/asio.hpp:20,
                 from serialsap.h:8,
                 from serialsap.cpp:1:
/usr/local/include/boost-1_37/boost/asio/detail/pipe_select_interrupter.hpp: In member function ‘void boost::asio::detail::pipe_select_interrupter::interrupt()’:
/usr/local/include/boost-1_37/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
gcc.compile.c++ bin/gcc-4.3.2/release/protocol.o
gcc.link bin/gcc-4.3.2/release/foo
...updated 3 targets...

Only occurs on release-mode, debug-mode works fine.

gcc -v
Using built-in specs.
Target: x86_64-linux-gnu
...
et=x86_64-linux-gnu
Thread model: posix
gcc version 4.3.2 (Ubuntu 4.3.2-1ubuntu11)

not important but would be nice to fix..

MfG

anonymous — Wed, 07 Jan 2009 12:44:35 GMT

This happens also in boost_1_37_0/boost/asio/detail/eventfd_select_interrupter.hpp.

Is the workaround suggested here safe? The warning is there for a good reason, I presume.

These are my details:

uname -a

Linux compilator 2.6.27-9-server #1 SMP Thu Nov 20 22:53:41 UTC 2008 i686 GNU/Linux

g++ -c -o myxxxfile.o -O3 -I../boost_1_37_0/ -MP -MD myxxxfile.cpp
In file included from ../boost_1_37_0/boost/asio/detail/select_interrupter.hpp:24,
                 from ../boost_1_37_0/boost/asio/detail/epoll_reactor.hpp:42,
                 from ../boost_1_37_0/boost/asio/impl/io_service.ipp:25,
                 from ../boost_1_37_0/boost/asio/io_service.hpp:550,
                 from ../boost_1_37_0/boost/asio/basic_io_object.hpp:20,
                 from ../boost_1_37_0/boost/asio/basic_socket.hpp:24,
                 from ../boost_1_37_0/boost/asio/basic_datagram_socket.hpp:25,
                 from ../boost_1_37_0/boost/asio.hpp:20,
                 from stdafx.h:22,
                 from myxxxfile.cpp:1:
../boost_1_37_0/boost/asio/detail/eventfd_select_interrupter.hpp: In member function 'void boost::asio::detail::eventfd_select_interrupter::interrupt()':
../boost_1_37_0/boost/asio/detail/eventfd_select_interrupter.hpp:89: warning: ignoring return value of 'ssize_t write(int, const void*, size_t)', declared with attribute warn_unused_result

status changed; resolution set

chris_kohlhoff — Sun, 01 Feb 2009 12:28:13 GMT

status new → closed
resolution → fixed

(In [50946]) Suppress unused result warning. Fixes #2534.

chris_kohlhoff — Wed, 04 Feb 2009 06:22:51 GMT

(In [51004]) Merged revisions 50943-50950,50961-50964,50987 via svnmerge from https://svn.boost.org/svn/boost/trunk

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r50943 | chris_kohlhoff | 2009-02-01 22:37:18 +1100 (Sun, 01 Feb 2009) | 2 lines

Need to specify socket lib to link correctly on QNX. Fixes #2504.

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r50944 | chris_kohlhoff | 2009-02-01 22:42:09 +1100 (Sun, 01 Feb 2009) | 2 lines

Use correct size for IP_MULTICAST_LOOP option on QNX. Fixes #2530.

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r50945 | chris_kohlhoff | 2009-02-01 22:57:01 +1100 (Sun, 01 Feb 2009) | 2 lines

Improve warning message when _WIN32_WINNT is not correctly defined. Fixes #2541.

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r50946 | chris_kohlhoff | 2009-02-01 23:28:12 +1100 (Sun, 01 Feb 2009) | 2 lines

Suppress unused result warning. Fixes #2534.

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r50947 | chris_kohlhoff | 2009-02-01 23:41:01 +1100 (Sun, 01 Feb 2009) | 3 lines

Ensure arguments to windows::overlapped_ptr::complete() are passed through to the completion handler. Fixes #2614.

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r50948 | chris_kohlhoff | 2009-02-01 23:50:08 +1100 (Sun, 01 Feb 2009) | 2 lines

Add include of <cstring> to fix a compile error on Solaris 10. Fixes #2607.

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r50949 | chris_kohlhoff | 2009-02-02 00:25:05 +1100 (Mon, 02 Feb 2009) | 3 lines

Clear the last error following a successful Windows API call, since some socket providers may leave last error set even when the call succeeds.

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r50950 | chris_kohlhoff | 2009-02-02 00:42:33 +1100 (Mon, 02 Feb 2009) | 2 lines

Fix errors in SSL overview and add a note about handshaking. Fixes #2617 and #2619.

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r50961 | chris_kohlhoff | 2009-02-02 17:18:59 +1100 (Mon, 02 Feb 2009) | 2 lines

Use a pipe if eventfd is not supported at runtime. Fixes #2683.

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r50962 | chris_kohlhoff | 2009-02-02 18:06:00 +1100 (Mon, 02 Feb 2009) | 2 lines

Add link to asio wiki.

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r50963 | chris_kohlhoff | 2009-02-02 20:36:11 +1100 (Mon, 02 Feb 2009) | 4 lines

Use the workaround syntax for specifying a return type with boost::bind. Needed for the SSL support to work on some older compilers (in particular, g++ 3.4.5 as used with MinGW).

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r50964 | chris_kohlhoff | 2009-02-02 20:37:10 +1100 (Mon, 02 Feb 2009) | 2 lines

Update asio version number.

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r50987 | chris_kohlhoff | 2009-02-03 22:00:39 +1100 (Tue, 03 Feb 2009) | 2 lines

Fix generated documentation where the overloads of a function have different brief descriptions.

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anonymous — Wed, 29 Apr 2009 03:25:39 GMT

Replying to anonymous:

Is the workaround suggested here safe? The warning is there for a good reason, I presume.

AFAIK, the result of a write() should always be checked: the socket or NFS may have gone down, the drive could be full, etc. If this case is just debugging information, or some kind of optional output, ignoring the status might be fine, but IMHO it needs comments to explicitly explain why it is safe.