To make it clear that some functions should not modify the variable
object, this patch adds the const qualifier where it makes sense to some
struct varobj * parameters. Most getters should take a const pointer to
guarantee they don't modify the object.
Unfortunately, I couldn't add it to some callbacks (such as name_of_child).
In the C implementation, they call c_describe_child, which calls
varobj_get_path_expr. varobj_get_path_expr needs to modify the object in
order to cache the computed value. It therefore can't take a const
pointer, and it affects the whole call chain. I suppose that's where you
would use a "mutable" in C++.
I did that to make sure there was no other cases like the one fixed in
the previous patch. I don't think it can hurt.
gdb/ChangeLog:
* ada-varobj.c (ada_number_of_children): Constify struct varobj *
parameter.
(ada_name_of_variable): Same.
(ada_path_expr_of_child): Same.
(ada_value_of_variable): Same.
(ada_value_is_changeable_p): Same.
(ada_value_has_mutated): Same.
* c-varobj.c (varobj_is_anonymous_child): Same.
(c_is_path_expr_parent): Same.
(c_number_of_children): Same.
(c_name_of_variable): Same.
(c_path_expr_of_child): Same.
(get_type): Same.
(c_value_of_variable): Same.
(cplus_number_of_children): Same.
(cplus_name_of_variable): Same.
(cplus_path_expr_of_child): Same.
(cplus_value_of_variable): Same.
* jv-varobj.c (java_number_of_children): Same.
(java_name_of_variable): Same.
(java_path_expr_of_child): Same.
(java_value_of_variable): Same.
* varobj.c (number_of_children): Same.
(name_of_variable): Same.
(is_root_p): Same.
(varobj_ensure_python_env): Same.
(varobj_get_objname): Same.
(varobj_get_expression): Same.
(varobj_get_display_format): Same.
(varobj_get_display_hint): Same.
(varobj_has_more): Same.
(varobj_get_thread_id): Same.
(varobj_get_frozen): Same.
(dynamic_varobj_has_child_method): Same.
(varobj_get_gdb_type): Same.
(is_path_expr_parent): Same.
(varobj_default_is_path_expr_parent): Same.
(varobj_get_language): Same.
(varobj_get_attributes): Same.
(varobj_is_dynamic_p): Same.
(varobj_get_child_range): Same.
(varobj_value_has_mutated): Same.
(varobj_get_value_type): Same.
(number_of_children): Same.
(name_of_variable): Same.
(check_scope): Same.
(varobj_editable_p): Same.
(varobj_value_is_changeable_p): Same.
(varobj_floating_p): Same.
(varobj_default_value_is_changeable_p): Same.
* varobj.h (struct lang_varobj_ops): Consitfy some struct varobj *
parameters.
(varobj_get_objname): Constify struct varobj * parameter.
(varobj_get_expression): Same.
(varobj_get_thread_id): Same.
(varobj_get_frozen): Same.
(varobj_get_child_range): Same.
(varobj_get_display_hint): Same.
(varobj_get_gdb_type): Same.
(varobj_get_language): Same.
(varobj_get_attributes): Same.
(varobj_editable_p): Same.
(varobj_floating_p): Same.
(varobj_has_more): Same.
(varobj_is_dynamic_p): Same.
(varobj_ensure_python_env): Same.
(varobj_default_value_is_changeable_p): Same.
(varobj_value_is_changeable_p): Same.
(varobj_get_value_type): Same.
(varobj_is_anonymous_child): Same.
(varobj_value_get_print_value): Same.
(varobj_default_is_path_expr_parent): Same.
https://sourceware.org/ml/gdb-patches/2014-05/msg00383.html
The MI command -var-info-path-expression currently does not handle
non-anonymous structs / unions nested within other structs / unions,
it will skip parts of the expression. Consider this example:
## START EXAMPLE ##
$ cat ex.c
#include <string.h>
int
main ()
{
struct s1
{
int a;
};
struct ss
{
struct s1 x;
};
struct ss an_ss;
memset (&an_ss, 0, sizeof (an_ss));
return 0;
}
$ gcc -g -o ex.x ex.c
$ gdb ex.x
(gdb) break 18
Breakpoint 1 at 0x80483ba: file ex.c, line 18.
(gdb) run
Starting program: /home/user/ex.x
Breakpoint 1, main () at ex.c:18
18 return 0;
(gdb) interpreter-exec mi "-var-create an_ss * an_ss"
(gdb) interpreter-exec mi "-var-list-children an_ss"
^done,numchild="1",children=[child={name="an_ss.x",exp="x",numchild="1",type="struct s1",thread-id="1"}],has_more="0"
(gdb) interpreter-exec mi "-var-list-children an_ss.x"
^done,numchild="1",children=[child={name="an_ss.x.a",exp="a",numchild="0",type="int",thread-id="1"}],has_more="0"
(gdb) interpreter-exec mi "-var-list-children an_ss.x.a"
^done,numchild="0",has_more="0"
(gdb) interpreter-exec mi "-var-info-path-expression an_ss.x.a"
^done,path_expr="(an_ss).a"
(gdb) print (an_ss).a
There is no member named a.
## END EXAMPLE ##
Notice that the path expression returned is wrong, and as a result
the print command fails.
This patch adds a new method to the varobj_ops structure called
is_path_expr_parent, to allow language specific control over finding
the parent varobj, the current logic becomes the C/C++ version and is
extended to handle the nested cases. No other language currently uses
this code, so all other languages just get a default method.
With this patch, the above example now finishes like this:
## START EXAMPLE ##
$ gdb ex.x
(gdb) break 18
Breakpoint 1 at 0x80483ba: file ex.c, line 18.
(gdb) run
Starting program: /home/user/ex.x
Breakpoint 1, main () at ex.c:18
18 return 0;
(gdb) interpreter-exec mi "-var-list-children an_ss"
^done,numchild="1",children=[child={name="an_ss.x",exp="x",numchild="1",type="struct s1",thread-id="1"}],has_more="0"
(gdb) interpreter-exec mi "-var-list-children an_ss.x"
^done,numchild="1",children=[child={name="an_ss.x.a",exp="a",numchild="0",type="int",thread-id="1"}],has_more="0"
(gdb) interpreter-exec mi "-var-list-children an_ss.x.a"
^done,numchild="0",has_more="0"
(gdb) interpreter-exec mi "-var-info-path-expression an_ss.x.a"
^done,path_expr="((an_ss).x).a"
(gdb) print ((an_ss).x).a
$1 = 0
## END EXAMPLE ##
Notice that the path expression is now correct, and the print is a
success.
gdb/ChangeLog:
* ada-varobj.c (ada_varobj_ops): Fill in is_path_expr_parent
field.
* c-varobj.c (c_is_path_expr_parent): New function, moved core
from varobj.c, with additional checks.
(c_varobj_ops): Fill in is_path_expr_parent field.
(cplus_varobj_ops): Fill in is_path_expr_parent field.
* jv-varobj.c (java_varobj_ops): Fill in is_path_expr_parent
field.
* varobj.c (is_path_expr_parent): Call is_path_expr_parent varobj
ops method.
(varobj_default_is_path_expr_parent): New function.
* varobj.h (lang_varobj_ops): Add is_path_expr_parent field.
(varobj_default_is_path_expr_parent): Declare new function.
gdb/testsuite/ChangeLog:
* gdb.mi/var-cmd.c (do_nested_struct_union_tests): New function
setting up test structures.
(main): Call new test function.
* gdb.mi/mi2-var-child.exp: Create additional breakpoint in new
test function, continue into test function and walk test
structures.
