Initialization problem when calling Matlab from C

I have a dummyCore.c file produced by the the Matlab command "mcc -l dummyCore.m". The complete dummyCore.c is in the attachment. From my own main.c file, I call the function mlxDummyCore in dummyCore.c, but that call does not change the value of input and output mxArrays, because _mc_inst is NULL. There is no error message, but debugging shows that mclFeval does not complete. Related lines in main.c:

Function mlxDummyCore in dummyCore.c:

What can I do to fix the pointer _mcr_inst?