As of 0.5.20, g77 defaults to handling
(and related intrinsics, constants, functions, and so on)
in a manner that
makes direct debugging involving these types in Fortran
language mode difficult.
Essentially, g77 implements these types using an
internal construct similar to C's
struct, at least
as seen by the gcc back end.
Currently, the back end, when outputting debugging info with
the compiled code for the assembler to digest, does not detect
struct types as being substitutes for Fortran
As a result, the Fortran language modes of debuggers such as
gdb see these types as C
struct types, which
they might or might not support.
Until this is fixed, switch to C language mode to work with
COMPLEX type and then switch back to Fortran language
(In gdb, this is accomplished via `set lang c' and
either `set lang fortran' or `set lang auto'.)