Re: Enabling --enable-check-lisp-object-type by default on x86 and AMD64

[Paul Eggert <eggert@cs.ucla.edu>]

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On 05/03/2017 07:48 AM, Eli Zaretskii wrote:
>> Would it help to add a line "set print frame-arguments all" to
>> src/.gdbinit?
> Only partially.  People who report backtraces seldom bother to start
> GDB from the Emacs's src directory, let alone source .gdbinit by hand.
> Moreover, latest versions of GDB refuse to auto-load .gdbinit files
> from random directories, unless you put some magic in your ~/.gdbinit
> (which most people don't).

This problem is not new. It should be OK to continue ask developers to 
source .gdbinit, to compile with -O0, etc. If we can't assume that, the 
backtrace is already problematic, and the recent change doesn't make it 
much worse.

> this setting doesn't affect only
> Lisp_Object, it affects any non-scalar arguments, so it has
> non-trivial downsides of its own (which I guess is why it is not the
> default).

True. How about using GDB pretty-printers instead?  E.g., add something 
like the attached file as src/gdb-pretty.py, and add the line "source 
gdb-pretty.py" to src/.gdbinit. That way, only Lisp_Object values are 
affected, rather than all structs.


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import gdb
import gdb.printing

class Lisp_Object_Printer:
    def __init__(self, val):
        self.val = val

    def to_string(self):
        return str (self.val["i"]) + "L"

def build_pretty_printer ():
    pp = gdb.printing.RegexpCollectionPrettyPrinter ("Emacs")
    pp.add_printer ('Lisp_Object', '^Lisp_Object$', Lisp_Object_Printer)
    return pp

gdb.printing.register_pretty_printer (gdb.current_objfile (),
                                      build_pretty_printer (),
                                      1)