vec_t not POD type build error with Clang and GCC about imguizmo HOT 7 CLOSED

$ g++-5 ImGuizmo.cpp 
ImGuizmo.cpp:188:11: error: 'struct ImGuizmo::matrix_t::<anonymous union>::vect' invalid; an anonymous union can only have non-static data members [-fpermissive]
    struct vect
           ^
$ g++-5 -v
Using built-in specs.
COLLECT_GCC=g++-5
COLLECT_LTO_WRAPPER=/usr/local/Cellar/gcc5/5.3.0/libexec/gcc/x86_64-apple-darwin15.4.0/5.3.0/lto-wrapper
Target: x86_64-apple-darwin15.4.0
Configured with: ../configure --build=x86_64-apple-darwin15.4.0 --prefix=/usr/local/Cellar/gcc5/5.3.0 --libdir=/usr/local/Cellar/gcc5/5.3.0/lib/gcc/5 --enable-languages=c,c++,objc,obj-c++,fortran --program-suffix=-5 --with-gmp=/usr/local/opt/gmp --with-mpfr=/usr/local/opt/mpfr --with-mpc=/usr/local/opt/libmpc --with-isl=/usr/local/opt/isl014 --with-system-zlib --enable-libstdcxx-time=yes --enable-stage1-checking --enable-checking=release --enable-lto --disable-werror --with-pkgversion='Homebrew gcc5 5.3.0' --with-bugurl=https://github.com/Homebrew/homebrew-versions/issues --enable-plugin --disable-nls --enable-multilib --with-native-system-header-dir=/usr/include --with-sysroot=/Applications/Xcode.app/Contents/Developer/Platforms/MacOSX.platform/Developer/SDKs/MacOSX10.11.sdk
Thread model: posix
gcc version 5.3.0 (Homebrew gcc5 5.3.0)

union
        {
            float m[4][4];
            float m16[16];
            struct
            {
                vec_t right, up, dir, position;
            } v;
        };