Re: Variable objects and STL containers

Nick Roberts
2008-02-10T21:02:56Z

> > > I anticipate that -var-update will:
> > >
> > > 1. Create new children, and report them.
> > > 2. Report children that are now gone, possibly deleting them.
> >
> > That sounds sensible. Discussion on the gcc mailing list suggested that
> > this should all be done in GDB, i.e., in C. I will explore that
> > possibility.
>
> Please note that I already have proof-of-concept Python integration,
> together with code to use Python for -var-evaluate-expression, together
> with not-yet-working patch to dynamically compute the list of varobj children.
> It might be better to wait till I got the last bit done.

Will the Python integration be self contained or does it require separate
libraries? Will it restrict the number of platforms that GDB builds on?

In any case, there seem to be two projects here: Python integration and the
display of STL containers using variable objects. It's not clear to me that
the former is necessary for the latter.

Below is just a quick sketch of the thoughts I have, which may or may not be
sensible.

In the case of vectors, var->num_children would be computed from n =
v._M_impl._M_finish - v._M_impl._M_start and the children would be created from
*(v._M_impl._M_start+1), *(v._M_impl._M_start+2), ...*(v._M_impl._M_start+n).

I guess a special variable object would need to be created for n and when it
was reported as changed bt -var-update, new/old variable objects could
accordingly be created/deleted.

--
Nick http://www.inet.net.nz/~nickrob

*** mi-cmd-var.c.~1.45.~ 2008-01-30 21:35:45.000000000 +1300
--- mi-cmd-var.c 2008-02-11 09:42:05.000000000 +1300
*************** mi_cmd_var_list_children (char *command,
*** 361,366 ****
--- 361,369 ----
int numchild;
enum print_values print_values;
int ix;
+ struct expression *expr;
+ struct value *value;
+ char* stl_member;

if (argc != 1 && argc != 2)
error (_("mi_cmd_var_list_children: Usage: [PRINT_VALUES] NAME"));
*************** mi_cmd_var_list_children (char *command,
*** 373,379 ****
if (var == NULL)
error (_("Variable object not found"));

! children = varobj_list_children (var);
ui_out_field_int (uiout, "numchild", VEC_length (varobj_p, children));
if (argc == 2)
print_values = mi_parse_values_option (argv[0]);
--- 376,390 ----
if (var == NULL)
error (_("Variable object not found"));

! stl_member = xstrprintf ("%s._M_impl", varobj_get_expression (var));
! expr = parse_expression (stl_member);
! if (gdb_evaluate_expression (expr, &value))
! // TODO: List children according to STL container.
! children = varobj_list_stl_children (var);
! else
! children = varobj_list_children (var);
! xfree (stl_member);
!
ui_out_field_int (uiout, "numchild", VEC_length (varobj_p, children));
if (argc == 2)
print_values = mi_parse_values_option (argv[0]);