[Fwd: Re: Request/question from RMS]

[Andrew Cagney]

Hello,

RMS pointed out that EMACS's GDB startup script contains lines like:

> define xreload
> set $valmask = ((long)1 << gdb_valbits) - 1
> set $nonvalbits = gdb_emacs_intbits - gdb_valbits
> end

and was asking about other ways of better handling this.  Well new to 
GDB 5.1 is the hookpost command vis:
    define hookpost-run
    set $valmask = ((long)1 << gdb_valbits) - 1
    set $nonvalbits = gdb_emacs_intbits - gdb_valbits
    end

which will be interpreted when ever a ``run'' command is executed.

Since this is only new, EMACS may need to hold back on exploiting this 
though :-/
Andrew
> --- Begin Message ---
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> Subject: 
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> Re: Request/question from RMS
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> Date: 
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> Thu, 10 Jan 2002 19:13:13 -0500
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> Mozilla/5.0 (X11; U; NetBSD macppc; en-US; rv:0.9.7) Gecko/20020103
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> > Date: Thu, 10 Jan 2002 09:45:26 -0500
> > > From: Andrew Cagney <address@hidden>
> > > > In Emacs .gdbinit I found this:
> > > > 
> > > > define xreload
> > > > set $valmask = ((long)1 << gdb_valbits) - 1
> > > > set $nonvalbits = gdb_emacs_intbits - gdb_valbits
> > > > end
> > [...]
> >
> > > > I think GDB should avoid making this necessary--that it should
> > > > reread .gdbinit when it reloads the executable.  Or there should
> > > > be a certain user-defined command that will be run after GDB
> > > > reloads the executable.
> > > I know there are now things like posthook-run commands.  However, 
> > > without knowing how EMACS uses the above (I've no desire to debug emacs, 
> > > debugging mozilla was scary enough :-^) it is hard to suggest a replacement.
> >
> > Here's an example of how this is used:
> >
> >     define xint
> >     print (($ & $valmask) << $nonvalbits) >> $nonvalbits
> >     end
> >     document xint
> >     Print $, assuming it is an Emacs Lisp integer.  This gets the sign right.
> >     end
> >     define xsymbol
> >     print (struct Lisp_Symbol *) ((((int) $) & $valmask) | gdb_data_seg_bits)
> >     output (char*)$->name->data
> >     echo \n
> >     end
> >     document xsymbol
> >     Print the name and address of the symbol $.
> >     This command assumes that $ is an Emacs Lisp symbol value.
> >     end
>
> Ok.
>
> This suggests that:
>
>         define hookpost-run
>         set $valmask = ((long)1 << gdb_valbits) - 1
>         set $nonvalbits = gdb_emacs_intbits - gdb_valbits
>         end
>
> should do the trick.
>
>         Andrew
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