title: Are some libraries in Boost 1.69 not compatible with MacOS?
body: <p>I am trying to compile a program that I have had no issues compiling with Ubuntu 18.04 and Windows 10. However, when I try to compile it on OSX High Sierra I am given errors and they are only related to boost.</p>
  
  <p>This is an example:</p>
  
  <pre><code>#include &lt;boost/process.hpp&gt;
  #include &lt;iostream&gt;
  
  int main()
  {
    std::cout &lt;&lt; "This is a test." &lt;&lt; std::endl;
  }
  </code></pre>
  
  <p>I have then tried to compile the program with both <code>g++</code> and <code>clang</code> like this:</p>
  
  <pre><code>g++ -std=c++11 test.cpp -lpthread
  </code></pre>
  
  <p>I then get this massive error:</p>
  
  <pre><code>In file included from test.cpp:1:
  In file included from /usr/local/include/boost/process.hpp:24:
  In file included from /usr/local/include/boost/process/async_system.hpp:22:
  In file included from /usr/local/include/boost/process/child.hpp:21:
  In file included from /usr/local/include/boost/process/detail/child_decl.hpp:30:
  /usr/local/include/boost/process/detail/posix/wait_for_exit.hpp:60:7: error: expected unqualified-id
      ::sigemptyset(&amp;sigset);
        ^
  /Applications/Xcode.app/Contents/Developer/Platforms/MacOSX.platform/Developer/SDKs/MacOSX.sdk/usr/include/signal.h:125:26: note: expanded from macro 'sigemptyset'
  #define sigemptyset(set)        (*(set) = 0, 0)
                                  ^
  In file included from test.cpp:1:
  In file included from /usr/local/include/boost/process.hpp:24:
  In file included from /usr/local/include/boost/process/async_system.hpp:22:
  In file included from /usr/local/include/boost/process/child.hpp:21:
  In file included from /usr/local/include/boost/process/detail/child_decl.hpp:30:
  /usr/local/include/boost/process/detail/posix/wait_for_exit.hpp:61:7: error: expected unqualified-id
      ::sigaddset(&amp;sigset, SIGCHLD);
        ^
  /Applications/Xcode.app/Contents/Developer/Platforms/MacOSX.platform/Developer/SDKs/MacOSX.sdk/usr/include/signal.h:122:31: note: expanded from macro 'sigaddset'
  #define sigaddset(set, signo)   (*(set) |= __sigbits(signo), 0)
                                  ^
  In file included from test.cpp:1:
  In file included from /usr/local/include/boost/process.hpp:24:
  In file included from /usr/local/include/boost/process/async_system.hpp:22:
  In file included from /usr/local/include/boost/process/child.hpp:21:
  In file included from /usr/local/include/boost/process/detail/child_decl.hpp:30:
  /usr/local/include/boost/process/detail/posix/wait_for_exit.hpp:87:26: error: no member named 'sigtimedwait' in the global namespace
          auto ret_sig = ::sigtimedwait(&amp;sigset, nullptr, &amp;ts);
                         ~~^
  In file included from test.cpp:1:
  In file included from /usr/local/include/boost/process.hpp:25:
  In file included from /usr/local/include/boost/process/group.hpp:32:
  /usr/local/include/boost/process/detail/posix/wait_group.hpp:64:7: error: expected unqualified-id
      ::sigemptyset(&amp;sigset);
        ^
  /Applications/Xcode.app/Contents/Developer/Platforms/MacOSX.platform/Developer/SDKs/MacOSX.sdk/usr/include/signal.h:125:26: note: expanded from macro 'sigemptyset'
  #define sigemptyset(set)        (*(set) = 0, 0)
                                  ^
  In file included from test.cpp:1:
  In file included from /usr/local/include/boost/process.hpp:25:
  In file included from /usr/local/include/boost/process/group.hpp:32:
  /usr/local/include/boost/process/detail/posix/wait_group.hpp:65:7: error: expected unqualified-id
      ::sigaddset(&amp;sigset, SIGCHLD);
        ^
  /Applications/Xcode.app/Contents/Developer/Platforms/MacOSX.platform/Developer/SDKs/MacOSX.sdk/usr/include/signal.h:122:31: note: expanded from macro 'sigaddset'
  #define sigaddset(set, signo)   (*(set) |= __sigbits(signo), 0)
                                  ^
  In file included from test.cpp:1:
  In file included from /usr/local/include/boost/process.hpp:25:
  In file included from /usr/local/include/boost/process/group.hpp:32:
  /usr/local/include/boost/process/detail/posix/wait_group.hpp:90:17: error: no member named 'sigtimedwait' in the global namespace
          ret = ::sigtimedwait(&amp;sigset, nullptr, &amp;ts);
                ~~^
  6 errors generated.
  </code></pre>
  
  <p>I could be missing a compiler flag, I have tried <code>-lboost_system</code> but that gave the same exact errors. If this specific library is not compatible with OSX then I will try and find a work around, but this library is already embedded in the code that I am currently working with. </p>
  
  <p>Are there any known fixes for this?</p>