Catching fortran runtime errors and signals in C++ binding

Question

I would like to be able to catch a terminating Fortran runtime errors in a C++ binding. I have a legacy F90 code to bind to and expect all kind of errors e.g. numerical, IO etc.

I managed to handle STOP according to: Intercepting Fortran STOP from C++ and able to throw/catch exception for this case in the C++ code.

I got some understanding 'Signal Handling in Fortran' at https://www.sharcnet.ca/help/images/4/42/Fortran_Signal_Handling.pdf

However I do not manage with this, an example for f90 fortran would be very helpful.

For example trying to open a non existant file in the fortran subroutine would give a runtime error, and the C++ code terminates:

open (unit=13,FILE="fnameBAD",status="old",action="read",position="rewind")

Fortran runtime error: Cannot open file 'fnameBAD': No such file or directory

I would like to be able to catch this and other runtime errors using signals.

Answer 1

This won't work, at least for GFortran. When then OPEN statement fails, the GFortran runtime library will shut itself down, and only finally is the signal generated. So by the time you can catch the signal in the signal handler, libgfortran has already shut itself down (including closing all open files).

The solution, as Vladimir F says in a comment, is to catch the error in the OPEN statement with the iostat= specifier.