GDB testsuite questions

[David Taylor <dtaylor@emc.com>]

It's been more than a decade since I did anything significant in DejaGNU
or Tcl (and I've never really cared for Tcl as a language), so these
questions are probably easy for someone who uses it regularly.

I have two sets of changes to GDB held up while I figure these out --

. how to grab part of the each of the responses to multiple gdb commands
and do arithmetric on the result to decide whether the test failed or
passed.

More specifically testing a fix for bug 17520 (structure offset wrong
when 1/4 GB or greater).

While more of our structures are 'reasonably' sized, a few are rather
large.  If you have a structure where some members are 1/4 GB or more
bytes from the start of the structure, GDB will calculate the wrong
offset for the member.

So, given the structure:

    struct big_struct
    {
      char first[0x10000000 + 16];
      long second;
    } big_struct;

in GDB 7.8, I did:

   (gdb) print &big_struct
    $1 = (struct big_struct *) 0x601040 <big_struct>
    (gdb) print &big_struct.second
    $2 = (long *) 0xfffffffff0601050

So, I want to take the addresses and compare the difference vs what it
should be.

. I also need to be able to disable it for targets that don't have
enough memory.  The program does not need to be downloaded or run; but,
if the link fails, disable the test.

As part of the bug fix a total of 33 files were modified.  There are no
regressions on x86-64 Linux, but there needs to be a new test to make
sure the problem does not reoccur.

The other set of changes that is yet to be submitted for approval
involves extending the agent bytecode expressions to allow setting
variables (useful when a breakpoint is hit).  How do I force the
testsuite to run against gdbserver?  I have gdbserver changes and I want
them tested.  I also need to write the new tests...