Proposal: offset based member name (or type) lookup

[Christoph Jaeschke <cjaeschke at onlinehome dot de>]

Hi,

I would like to propose a offset based member name lookup of
structs/classes. Assume:

    struct X {
        int a;
        int b;
    };

    struct Y {
        struct X x[4];
        int c;
    };

    struct Z {
        Y  y;
    };

If you apply a patch for gdb 6.0 I've prepared, you can ask gdb by

    ptype Z + 28

about Z's relative name at offset 28

    .y.x[3].b

using

    ptype Z+28, typechain

gdb will append also the typechain

    .y.x[3].b, typechain = ::Y::X[4]::int


There may be a better suited command than 'ptype' for it, it was choosen 
just because it was the simplest way to add it.

The patch contains also a caching mechanism, speeding up a lot if you do 
many lookups in big nested structures. It has a minimal memory 
requirement and will not hurt for single lookups.

The patch can be send if you are interested in.

    Christoph Jaeschke