Comparing tree types

[Vini Kanvar <vini at cse dot iitb dot ac dot in>]

I am trying to compare the tree declarations of the lhs and the rhs of
the assignment statement in the following program.

struct node {
        struct node * next;
};
struct node ** obj1, obj2;
obj1 = &obj2.next;		// lhs is obj1, rhs is obj2.next

-----------
Let us call the following tree declaration of the lhs as "obj1_tree".
-------------
 <var_decl 0x405cc180 obj1
    type <pointer_type 0x405c5ea0
        type <pointer_type 0x405c5f00 type <record_type 0x405c5f60 node>
            unsigned SI
            size <integer_cst 0x40511578 constant 32>
            unit size <integer_cst 0x40511594 constant 4>
            align 32 symtab 0 alias set -1 canonical type 0x405cc000
            pointer_to_this <pointer_type 0x405c5ea0>>
        unsigned SI
        size <integer_cst 0x40511578 constant 32>
        unit size <integer_cst 0x40511594 constant 4>
        align 32 symtab 0 alias set -1 canonical type 0x405c5ea0>
    used unsigned SI file structstruct2.c line 8 col 17
    size <integer_cst 0x40511578 type <integer_type 0x40521060
bitsizetype> constant 32>
    unit size <integer_cst 0x40511594 type <integer_type 0x40521000
sizetype> constant 4>
    align 32 context <function_decl 0x405c9080 main> chain <var_decl
0x405cc1e0 obj2>>

-------------
Let us call the following tree declaration of the rhs as
"obj2.next_tree"
-------------
 <field_decl 0x4051f0b8 next
    type <pointer_type 0x405cc000
        type <record_type 0x405c5f60 node SI
            size <integer_cst 0x40511578 constant 32>
            unit size <integer_cst 0x40511594 constant 4>
            align 32 symtab 0 alias set -1 canonical type 0x405c5f60
fields <field_decl 0x4051f0b8 next> context <translation_unit_decl
0x40526804 D.2319>
            pointer_to_this <pointer_type 0x405c5f00> chain <type_decl
0x40526870 node>>
        unsigned SI
        size <integer_cst 0x40511578 constant 32>
        unit size <integer_cst 0x40511594 constant 4>
        align 32 symtab 0 alias set -1 canonical type 0x405cc000
        pointer_to_this <pointer_type 0x405cc060>>
    used unsigned nonlocal SI file structstruct2.c line 3 col 16
    size <integer_cst 0x40511578 type <integer_type 0x40521060
bitsizetype> constant 32>
    unit size <integer_cst 0x40511594 type <integer_type 0x40521000
sizetype> constant 4>
    align 32 offset_align 128
    offset <integer_cst 0x405115b0 type <integer_type 0x40521000
sizetype> constant 0>
    bit offset <integer_cst 0x4051163c type <integer_type 0x40521060
bitsizetype> constant 0> context <record_type 0x405c5f60 node> chain
<type_decl 0x405268dc node>>
-------------

Please note from the above tree declarations that 
Type1 = TREE_TYPE (TREE_TYPE (obj1_tree)) = 0x405c5f00
Type2 = TREE_TYPE (obj2.next_tree) = 0x405cc000
Type3 = TYPE_POINTER_TO (TREE_TYPE (TREE_TYPE (obj2.next_tree))) =
0x405c5f00

I was expecting Type1 and Type2 to be equal because obj1=&obj2.next.
However, in this case, we see that Type1 and Type3 are equal. Please
explain this.

Also, what is the meaning of "pointer_to_this" in the tree declarations?

Thanks and regards,
Vini Kanvar.