Re: [patch] Fix glitches with libstdc++ pretty printers

[Tom Tromey <tromey at redhat dot com>]

>>>>> "Paul" == Paul Pluzhnikov <ppluzhnikov@google.com> writes:

Paul> Hmm, an easy way to solve this would be to say that if Foo inherits
Paul> from Bar, and if Bar has a pretty-printer but Foo doesn't, then
Paul> the Bar pretty-printer is used.

Paul> With that, I only need to define one pretty-printer :)

This same problem came up in the GObject context.

I do wonder whether regexp on the type name is the best way to
associate types with printer constructors.


One idea I had was that the -gdb.py code could iterate over the types
defined in the current objfile and set up the dictionary using the
results.  We'd have to write some more Python glue to make this
possible, but we'll need that anyway.

This would let you implement printing-via-inheritance.  We could even
supply a utility function to make it simple.

The down side of this approach is that (I think) it requires loading
the symbols, which interacts poorly with the lazy-reading branch,
which we also want.


Another idea is to run a hook when a type is created, and do the
association directly, not by name.  My worry here is that we'd see a
noticeable performance hit.


Finally, you can do it already, with a bit of difficulty.  You can
install a printer constructor for any struct type, and then have it
examine the type hierarchy.  If the desired ancestor is not found, it
can return None, and the C code will look for the next printer.  You
can even register the newly discovered type in the map for faster
access the next time.

I imagine this is pretty slow, but I have not tried it.  I think it
would be preferable to come up with something nicer if we can.

Right now I'm not sure what exactly I want to do.  Gathering
requirements is always a good first step...

Tom