Today (23 Jan 2004) I changed the Xtensa port to define SPLIT_COMPLEX_ARGS so
that _Complex function arguments are split into separate real and imaginary
parts.  After that change, I noticed that I couldn't see any _Complex arguments
from GDB.  The following input will demonstrate the problem:

_Complex int cmplx (_Complex int arg) { return arg; }

int main (void) {
  _Complex int c = (1,2);
  c = cmplx(c);
  return 0;
}

With the default of DWARF2 for this target, the "formal parameter" TAG for "arg"
is produced but it has no AT_location entry.  If I use "-gstabs", there is no
".stabs" entry at all for "arg".

I'm not aware of anything specific to the Xtensa port that would cause this, so
the same problem is likely to occur with other ports that define
SPLIT_COMPLEX_ARGS (currently alpha and rs6000/AIX).