Expr constructor question

["Weihaw Chuang" <weihawchuang at hotmail dot com>]

Hi all,
Hopefully this is the right mailing list for discussions about GCC 
internals.  My end goal is to modify the Greg McGary's bounds checker, but 
in the following I just want to figure out "struct" initialization.

At the highest level, can someone tell me why the following is causes an 
error:
#include <stdio.h>
struct record {
   int a;
};

struct record object;
struct record * ptr = &object;
struct record * ptr2 = ptr;        // <============ problem

int main()
{
   printf("done");}

> gcc rec2.c -S
rec2.c:8: initializer element is not constant
If I remove the problem line, then the compiler message goes away.  Now 
putting aside C rules, say I want to do use the problem line, and am willing 
to assume that ptr2 always has the same value as ptr.  Could I have two 
identifiers "ptr" and "ptr2" in the front-end point to the same VAR_DECL 
record pointer?   Another route is change the declaration mechanism.  The 
problem here is that there is a great deal of guard code in 
c-typeck.c/digest_init involving TREE_CONSTANT checks.  Why are these checks 
needed?

Many thanks,
-Wei

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