This section describes how exceptions are implemented in GNU Modula-2 and how command line switches affect their behavior. The option ‘-fsoft-check-all’ enables all software checking of nil dereferences, division by zero etc. Additional code is produced to check these conditions and exception handlers are invoked if the conditions prevail.
Without ‘-fsoft-check-all’ these exceptions will be caught by
hardware (assuming the hardware support exists) and a signal handler
is invoked. The signal handler will in turn THROW an exception
which will be caught by the appropriate Modula-2 handler. However the
action of throwing an exception from within a signal handler is
implementation defined (according to the C++ documentation). For
example on the x86_64 architecture this works whereas on the i686
architecture it does not. Therefore to ensure portability it is
recommended to use ‘-fsoft-check-all’.
‘-fsoft-check-all’ can be effectively combined with ‘-O2’ to semantically analyze source code for possible run time errors at compile time.