Add check to make sure POSIX functions are available in Cygwin.

Author: igaztanaga

include/boost/interprocess/detail/workaround.hpp

@@ -34,6 +34,10 @@
 #else
    #include <unistd.h>
 
+   #if defined (__CYGWIN__) && (!defined(_POSIX_C_SOURCE) && (_POSIX_C_SOURCE < 200112L))
+   #error "Error: Compiling on Cygwin without POSIX is not supported. Please define _XOPEN_SOURCE >= 600 or _POSIX_C_SOURCE >= 200112 when compiling"
+   #endif
+
    //////////////////////////////////////////////////////
    //Check for XSI shared memory objects. They are available in nearly all UNIX platforms
    //////////////////////////////////////////////////////

test/Jamfile.v2

@@ -25,7 +25,7 @@ project : requirements
     <target-os>hpux,<toolset>gcc:<linkflags>"-Wl,+as,mpas"
     <target-os>windows,<toolset>clang:<linkflags>"-lole32 -loleaut32 -lpsapi -ladvapi32"
     <target-os>linux:<linkflags>"-lrt"
-    #cygwin with -std=c++XX does not include POSIX
+    #cygwin with -std=c++XX does not include POSIX features, so always request them
     <target-os>cygwin:<define>_XOPEN_SOURCE=600
     ;