GDB, examine pointer to pointer

Question

Ok, so I'm trying to learn gdb. I know most of the basics but I have not been able to figure out how to examine a pointer to a pointer in a oneliner. It might be possible by defining a macro/command but I haven't been able to do so.

This question began when learning the cdecl calling convention where $esp contained a pointer to a string, passed as an argument to a function. In order to get this out I had to do the following:

gdb$ x $esp+0x08
0xbffff6a4: 0x980eb192
gdb$ x/s 0x980eb192
0x980eb192:  "Hello world"

So, the question is. Can this be done in an easier way? Cutting and pasting just feels too slow.

Appreciate any hints/ideas!

Nikolai Fetissov · Accepted Answer · 2011-11-22 21:30:45Z

3

(gdb) x/s *(char**)($esp+8) might do the trick.

answered Nov 22, 2011 at 21:30

Nikolai Fetissov

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Comments

chill · Accepted Answer · 2011-11-22 21:38:10Z

1

You can reuse results of print in subsequent expressions:

(gdb) p *(void **)($esp + 4)
$4 = (void *) 0x80aec48
(gdb) x/s $4
0x80aec48:   "alabala"

answered Nov 22, 2011 at 21:38

chill

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