Comparing tree types

[Vini Kanvar]

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".
-
 
unsigned SI
size 
unit size 
align 32 symtab 0 alias set -1 canonical type 0x405cc000
pointer_to_this >
unsigned SI
size 
unit size 
align 32 symtab 0 alias set -1 canonical type 0x405c5ea0>
used unsigned SI file structstruct2.c line 8 col 17
size  constant 32>
unit size  constant 4>
align 32 context  chain >

-
Let us call the following tree declaration of the rhs as
"obj2.next_tree"
-
 
unit size 
align 32 symtab 0 alias set -1 canonical type 0x405c5f60
fields  context 
pointer_to_this  chain >
unsigned SI
size 
unit size 
align 32 symtab 0 alias set -1 canonical type 0x405cc000
pointer_to_this >
used unsigned nonlocal SI file structstruct2.c line 3 col 16
size  constant 32>
unit size  constant 4>
align 32 offset_align 128
offset  constant 0>
bit offset  constant 0> context  chain
>
-

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.

Registration deadline extended - Workshop on Essential Abstractions in GCC

[Vini Kanvar]

  Workshop on Essential Abstractions in GCC, 2011
  (http://www.cse.iitb.ac.in/grc/gcc-workshop-11)
  ---

Organized by: GCC Resource Center (http://www.cse.iitb.ac.in/grc).

Venue:Department of Computer Science and Engineering,
  IIT Bombay (http://www.cse.iitb.ac.in).

Dates:30 June to 3 July (Thursday to Sunday) 2011.

Extended
last date of
registration: Friday, 10 June 2011

---

Our apologies if

- you have received multiple copies of this notification, or
- if this notification has reached you erroneously.

Please forward this to people who you think might be interested.

GCC Resource Center Team

gcc4.7.2: try/finally, CLOBBER

[Vini Kanvar]

Hi,

gcc-4.7.2 adds exception handling constructs (try/finally block) for
pointer and array variables. These variables are CLOBBERed in the
finally block.

What is the meaning and use of CLOBBER? In which cases is it required?
What will happen if gcc does not CLOBBER these variables (e.g.
gcc-4.6.2 does not add try/finally and CLOBBER in the gimple code. How
does gcc-4.6.2 deal with such variables?).

Thanks and regards,

Vini Kanvar.