C++ runtime, display exception message

Question

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 << ex.what() << endl;
   }
}

You could write in main:

try{

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

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.

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.

GCC shows the message at least since 6.2.0

I had tested it on g++ 6.2.0, Ubuntu 16.10, and now again in g++ 9.3.0 Ubuntu 20.04, and both showed the message, not sure when behavior changed:

#include <stdexcept>

void myfunc() {
    throw std::runtime_error("my message");
}

int main() {
    myfunc();
}

compile and run:

g++ -ggdb3 -O0 -std=c++11 -Wall -Wextra -pedantic -o main.out main.cpp
./main.out

output containing the my message error message:

terminate called after throwing an instance of 'std::runtime_error'
  what():  my message