throw error from a matlab compiled dll

i have a matlab function say f.m which i have compilled to a c++ dll using mcc. i want to throw error from inside f.m. question is how do i catch it from the c++ code.

if function f(arg1,arg2) takes in a two arguments. the c++ signature is something like f(int argout, mwArray output, mwArray arg1, mwArray arg2). mwArray are defined within the matlab include files. mwArray output is where i get the output which can be defined as something like mwArray output(row,col,mxDOUBLE_CLASS).

i do not see how i can get back the thrown error in mwArray output which is defined as double.