C++ runtime, display exception message

Question

hello.

I am using gcc on linux to compile C++ code. There are some exceptions which should not be handled and should close program. However, I would like to be able to display exception string:

For example:

throw std::runtime_error(" message"); does not display message, only type of error. I would like to display messages as well. Is there way to do it?

it is a library, I really do not want to put catch statements and let library user decide. However, right now library user is fortran, which does not allow to handle exceptions. in principle, I can put handlers in wrapper code, but rather not to if there is a way around

Thanks

Answer 1

Standard exceptions have a virtual what() method that gives you the message associated with the exception:

int main() {
   try {
       // your stuff
   }
   catch( const std::exception & ex ) {
       cerr << e.what() << endl;
   }
}

Answer 2

You could write in main:

try{

}catch(const std::exception &e){
   std::cerr << e.what() << std::endl;
   throw;
}

Answer 3

You could use try/catch block and throw; statement to let library user to handle the exception. throw; statement passes control to another handler for the same exception.

Answer 4

I recommend making an adapter for your library for fortran callers. Put your try/catch in the adapter. Essentially your library needs multiple entry points if you want it to be called from fortran (or C) but still allow exceptions to propigate to C++ callers. This way also has the advantage of giving C++ linkage to C++ callers. Only having a fortran interface will limit you substantially in that everything must be passed by reference, you need to account for hidden parameters for char * arguments etc.