Description:

From the upstream bug report https://savannah.gnu.org/bugs/?38746 :

When including mex.h from a C++ source file, and compiling with G++ 4.8, the compilation crashes.

Despite available patches, this bug report has not received any attention from upstream for several weeks. When asking about support for g++ 4.8 on the mailing list I also got no reply. I doubt that this will ever be fixed any time soon, and will probably be an issue still with the next major release.

I therefore suggest applying the patch attached to the bug report. Otherwise Arch users will remain unable to use C++ mex files with Octave.

Additional info:

octave 3.6.4-1
gcc 4.8.0-4

Steps to reproduce:

$ cat >mex_empty.cpp <<EOF
#include "mex.h"
void mexFunction(int nlhs, mxArray* plhs[], int nrhs, const mxArray* prhs[]) {}
EOF
$ octave --eval 'mex mex_empty.cpp'
In file included from /usr/include/octave-3.6.4/octave/mexproto.h:52:0,
from /usr/include/octave-3.6.4/octave/mex.h:77,
from mex_empty.cpp:1:
/usr/include/c++/4.8.0/cstdlib: In function ‘long long int std::abs(long long int)’:
/usr/include/c++/4.8.0/cstdlib:174:20: error: declaration of C function ‘long long int std::abs(long long int)’ conflicts with
abs(long long __x) { return __builtin_llabs (__x); }
^
/usr/include/c++/4.8.0/cstdlib:166:3: error: previous declaration ‘long int std::abs(long int)’ here
abs(long __i) { return __builtin_labs(__i); }
^
[...]