[Bug fortran/101135] Load of null pointer when passing absent assumed-shape array argument for an optional dummy argument

[anlauf at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=101135

--- Comment #4 from anlauf at gcc dot gnu.org ---
Created attachment 52311
  --> https://gcc.gnu.org/bugzilla/attachment.cgi?id=52311&action=edit
Patch that regtests ok.

The patch suggested by the reporter is rather close to this one.

We need to special-case optional arguments of procedures with bind(c)
attribute.  I haven't understood the details yet, but excluding those
prevents regressions in the c-binding testsuite, e.g. bind-c-contiguous-4.*.

We need to fix the pattern for testcase
gfortran.dg/missing_optional_dummy_6a.f90
which would have failed with -fsanitize=undefined without this patch.