Re: print/x on references

Douglas Evans
2007-10-18T17:10:35Z

On 10/18/07, Douglas Evans <dje@google.com> wrote:
> To find the address of the pointer to the object I was thinking "p
> &(&x)". It works, at least in the simple example I used to experiment
> with.
>
> Am I misunderstanding your point? [quite likely - apologies]

Heh ... or used too simplistic an example. Here it is fwiw.

class c
{
int i;
};

void
foo (c& cref)
{
}

int
main ()
{
c cobj;
foo (cobj);
}

dje@ruffy:~/src$ gdb a.out
GNU gdb 6.7.50-20071017-cvs
Copyright (C) 2007 Free Software Foundation, Inc.
License GPLv3+: GNU GPL version 3 or later <http://gnu.org/licenses/gpl.html>
This is free software: you are free to change and redistribute it.
There is NO WARRANTY, to the extent permitted by law. Type "show copying"
and "show warranty" for details.
This GDB was configured as "i686-linux"...
Using host libthread_db library "/lib/tls/i686/cmov/libthread_db.so.1".
(gdb) b foo
Breakpoint 1 at 0x8048357: file ref-printing.cc, line 9.
(gdb) r
Starting program: /home/dje/src/a.out

Breakpoint 1, foo (cref=@0xffffd864) at ref-printing.cc:9
9 }
(gdb) info frame
Stack level 0, frame at 0xffffd840:
eip = 0x8048357 in foo(c&) (ref-printing.cc:9); saved eip 0x8048381
called by frame at 0xffffd870
source language c++.
Arglist at 0xffffd838, args: cref=@0xffffd864
Locals at 0xffffd838, Previous frame's sp is 0xffffd840
Saved registers:
ebp at 0xffffd838, eip at 0xffffd83c
(gdb) p cref
$1 = (c &) @0xffffd864: {i = 1334422496}
(gdb) p &cref
$2 = (c *) 0xffffd864
(gdb) p &(&cref)
$3 = (c **) 0xffffd840
(gdb) x/4x $ebp
0xffffd838: 0xffffd868 0x08048381 0xffffd864 0x416ed604
(gdb)