Re: [RFC PATCH] gdb/py: Add pretty printer for __mfp8 for aarch64

[Andrew Burgess <aburgess@redhat.com>]

<Ezra.Sitorus@arm.com> writes:

> From: Ezra Sitorus <ezra.sitorus@arm.com>
>
> __mfp8/mfloat8_t is encoded as unsigned int in DWARF so we are unable to
> print out variables of this type properly. As a result, this patch adds
> a python pretty printer to display these values. To use:

Pretty printers are usually defined alongside the library that adds the
types that need pretty printing.  But (from a quick google search) it
would seem that these types are ARM extensions to the C language, and so
are present in most/all C compilers for ARM targets?

Given that adding pretty printers to GDB is unusual, I think it is worth
including a justification for why the pretty printers should be added
here, and not with the compiler.

> import gdb.printer
> gdb.printer.register_aarch64_fp8_printer(gdb.current_objfile())

I think you ideally want these to be automatically registered, just how
compiler pretty printers would be automatically loaded.

You should investigate the 'new_objfile' event.  But I'm not certain how
you're going to decide if the pretty printer should be registered or
not as you'll only want to register this for suitable AArch64 inferiors
I guess.  Maybe there's something that could be done via the program
space? 

My concern is that if these printers don't auto-register then users
aren't going to know this feature exists.

Remember, we can always extend the Python API to add the features you
need to make it possible to auto-register ... we just need to know what
you need :)

Thanks,
Andrew