Re: [Qemu-devel] [PATCH] qemu-gdb: add a QObject pretty printer

[Eduardo Habkost]

On Fri, Jan 18, 2019 at 05:48:43PM +0400, Marc-André Lureau wrote:
> Inspired by GObject/GType pretty printer.
> 
> Example:
> machine_set_accel (obj=0x555556807550 [pc-i440fx-4.0-machine],...
> 
> Signed-off-by: Marc-André Lureau <address@hidden>
> ---
>  scripts/qemu-gdb.py | 58 +++++++++++++++++++++++++++++++++++++++++++++
>  1 file changed, 58 insertions(+)
>  mode change 100644 => 100755 scripts/qemu-gdb.py
> 
> diff --git a/scripts/qemu-gdb.py b/scripts/qemu-gdb.py
> old mode 100644
> new mode 100755
> index 690827e6fc6..90c6fd13b93
> --- a/scripts/qemu-gdb.py
> +++ b/scripts/qemu-gdb.py
> @@ -21,6 +21,9 @@ import gdb
>  
>  import os, sys
>  
> +if sys.version_info[0] >= 3:
> +    long = int
[...]
> +class QObjectPrinter:
> +    def __init__(self, val):
> +        self.val = val
> +
> +    def to_string(self):
> +        name = object_class_name(self.val)
> +        if name:
> +            return ("0x%x [%s]")% (long(self.val), name)
> +        return  ("0x%x") % (long(self.val))

I took a while to find out that int(v) doesn't work if v is a
pointer gdb value.  This is surprising, because int(long_number)
(e.g. int(2**65)) works on Python 2.

Also, this works on Python 2:

  int(self.val.cast(gdb.lookup_type("unsigned long long")))

But it's so ugly that a sys.version_info check still sounds
better.

I would prefer this, though:

  if sys.version_info[0] < 3:
      int = long
  ...
      def to_string(self):
          ...
          return  ("0x%x") % (int(self.val))

Because it makes the python2-specific code easier to remove in
the future.

> +
> +
> +def lookup_type(val):
> +    if is_object(val):
> +        return QObjectPrinter(val)
> +    return None
> +
> +
> +gdb.pretty_printers.append(lookup_type)
> -- 
> 2.20.1.98.gecbdaf0899
> 

-- 
Eduardo