> In C, it would be "my_page_var.mapping".  The union is transparent.

Oh, I see. (love to learn new things :).

Back to the issue at hand, it therefore seems pretty desirable to
enhance the debugger in that case. Unfortunately, I don't think
the proposed patch is correct, because it bases the logic on the
size of the union/struct instead of whether the field is anonymous
or not. Do you agree?

Just for easier reference, the patch was:

2007-08-16   Carlos Eduardo Seo <cseo@linux.vnet.ibm.com>

        gdb/c-typeprint.c (c_type_print_base): check value of
        TYPE_NFIELDS (type) when displaying members of an
        unnamed struct inside an union.

This patch breaks the tests that I just posted for RFA:
http://www.sourceware.org/ml/gdb-patches/2007-08/msg00498.html
But otherwise is reported to not cause any other regression on
the testsuite.

-- 
Joel