On Jan 21, 2009, at 8:14 PM, Mon Ping Wang wrote:
> Hi,
>
> This patch fixes a case where we lose the address space when
> accessing a member of a structure. For example,
> consider
>
> typedef struct S {
> int arr[ 3 ];
> } S;
>
> __attribute__((address_space(1))) S* p1;
> p1->arr[2] = 4;
>
> The address space associated with p1->arr should be address space 1.
Hi Mon Ping,
I am not sure that this is the right approach. The embedded C spec
(which defines how address spaces work) says:
"The effective type of an object for an access to its stored value is
the declared type of the object, if any, without any address-space
qualifier that the declared type may have.72) If a value is stored into
an object having no declared type through an lvalue having a type that
is not a character type, then
the type of the lvalue, without any address-space qualifier, becomes
the effective type of the object
for that access and for subsequent accesses that do not modify the
stored value. "
I think that this means that the type of "p1->arr" should be "int[3]"
in your example, not "int[3] __addrspace(1)". In this case, the code
generator should generate the right address space qualifiers from the
l-value ("p1"), not from the expression type.
This is similar to how volatile or const works.
-Chris
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