Re: set print objct pros/cons [Re: [Keith Seitz] Re: [tools-team] Status 2008-09-01]

[Jan Kratochvil <jan.kratochvil@redhat.com>]

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On Sun, 27 Sep 2009 19:14:22 +0200, Keith Seitz wrote:
> On 09/27/2009 05:21 AM, Jan Kratochvil wrote:
> >
> >(1) Last "call basep->m ()" should have printed "derived::m"
> >     because "p basep->m" prints "Derived::m()", shouldn't it?
> >
> 
> basep->m will always print "base::m" -- your test case did not
> declare Base::m virtual. Or is that just an omission in the file you
> attached?

It was intentional that way (unaware how common it is in C++ to override
non-virtual method name by a virtual one, though).

I think the following two commands should deal with the same pointer, whithout
even talking about which pointer ("Derived::m" or "Base::m") it should be:

It does not work now - with the previous testcase cxxinherit.C:
	(gdb) set print object on
	(gdb) p basep->m
	$4 = {void (Derived *)} 0x4006c4 <Derived::m()>
	(gdb) call basep->m ()
	base::m


> IMO, "object print" should not even exist at all.

Currently the "off" mode does not work right for the virtual/virtual case:

With the new attached testcase cxxinherit2.C:
	Starting program: /home/jkratoch/t/cxxinherit2 
	derived::m
	derived::m
	Breakpoint 1, main () at cxxinherit2.C:27
	27	  return 0;
	(gdb) show print object 
	Printing of object's derived type based on vtable info is off.
	(gdb) call basep->m ()
	derived::m
	(gdb) p basep->m
	$1 = {void (Base *)} 0x4006a6 <Base::m()>
	(gdb) 


Regards,
Jan

[-- Attachment #2: cxxinherit2.C --]
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#include <stdio.h>

class Base
  {
  public:
    virtual void m () { puts ("base::m"); }
    virtual void stub () {}
  };

class Derived : public Base
  {
  public:
    virtual void m () { puts ("derived::m"); }
    virtual void stub () {}
  };

int
main ()
{
  Derived derived_local;
  Derived *derivedp = &derived_local;
  Base *basep = &derived_local;

  derivedp->m ();
  basep->m ();

  return 0;
}