Re: gdb and iterators

[llewelly]

glen_stark <stark@ifh.ee.ethz.ch> writes:

> Hi.
>
> I hope I'm posting in the correct forum.  I'm debugging some code
> using iterators, and having trouble getting info on where the iterator
> is pointing to, and what.
>
> i get:
>
> 1: spli = (t_shapePtrListIter &) @0x226b00: {<_List_iterator_base> = {
>      _M_node = 0xa042980}, <No data fields>}
>
> When I type "print spli"
>
> and
> Attempt to take contents of a non-pointer value.
>
> for "print *spli".  spli should be an list iterator pointing to
> pointer to a Shape (my own class).  Can someone tell me what's going
> on?  is there a trick to getting iterator info?

I'm using gdb 6.1 and g++ 3.3.3 . for me, print *i where i is
    list<int>::iterator reports something like:

(gdb) print *i
$1 = (int &) @0x804b018: 1

which is nice, but print *l.begin() dies horribly:

(gdb) print *l.begin()

Program received signal SIGBUS, Bus error.
0x08048b42 in std::list<int, std::allocator<int> >::begin
(this=0x281099ee) at /usr/include/c++/3.3/bits/stl_list.h:569 
The program being debugged was signaled while in a function called from GDB.
GDB remains in the frame where the signal was received.
To change this behavior use "set unwindonsignal on"
Evaluation of the expression containing the function (std::list<int,
std::allocator<int> >::begin()) will be abandoned. 


Personally, I almost never use gdb for debugging C++ code;
    cerr << "my message" ; seems less painful.