Re: casting in gdb

[Daniel Berlin <dberlin@dberlin.org>]

On Sat, 14 Dec 2002, Daniel Jacobowitz wrote:

> On Fri, Dec 13, 2002 at 02:43:17PM -0500, Jacques Le Normand wrote:
> > here you go, thanks for lending a hand...
> >
> > [countchocula@chocoland countchocula]$ g++ -ggdb test.cpp -o test.o
> > [countchocula@chocoland countchocula]$ gdb test.o
> > GNU gdb Red Hat Linux (5.2.1-4)
> > Copyright 2002 Free Software Foundation, Inc.
> > GDB is free software, covered by the GNU General Public License, and you are
> > welcome to change it and/or distribute copies of it under certain
> > conditions.
> > Type "show copying" to see the conditions.
> > There is absolutely no warranty for GDB.  Type "show warranty" for details.
> > This GDB was configured as "i386-redhat-linux"...
> > (gdb) b 10
> > Breakpoint 1 at 0x80486f5: file test.cpp, line 10.
> > (gdb) r
> > Starting program: /home/countchocula/test.o
> >
> > Breakpoint 1, main () at test.cpp:10
> > 10        a.push_back(2);
> > (gdb) p a[0]
> > One of the arguments you tried to pass to operator[] could not be converted
> > to w
> > hat the function wants.
> > (gdb)
>
> This one's pretty simple once you figure it out.  The error message is
> really bad; I'll hold on to this and try to improve it.
Hey now
I added that error message, because it was horrible before that.
Ahh, here we go:
2542c2542
<       error ("Argument list of %s mismatch with component in the
structure.", name);
---
>       error ("One of the arguments you tried to pass to %s could not be
converted to what the function wants.", name);


I remember i had a patch that added a seperate error message for the case
where the operator wasn't existing, but it's quite invasive.
Look at where that error message pops up.
You'll note you'd need to make search_struct_method take another argument
so we can tell if we couldn't *find* it, or we had a mismatch.


>
> Your program doesn't _use_ operator[].  So it doesn't get compiled into
> the program, and GDB can't call it to figure out what to do.
>
> What happens if you add a call to the operator?
>
> [I noticed some other quirks; for instance, if your program only uses
> the mutable version and GDB finds the const version first, it may get
> confused...]
>
> --
> Daniel Jacobowitz
> MontaVista Software                         Debian GNU/Linux Developer
>