IBM xlc support for hw/darwin/*

Hello,

I'am currently testing IBM's xlc compiler. For that I tried to compile 
the X11 project. 99% works good (and fast and stable too). Still open 
for me is the hw/darwin part.

As I tried to compile I got this error

"fullscreen.c", line 111.5: 1506-025 (S) Operand must be a modifiable 
lvalue.
"fullscreen.c", line 390.5: 1506-025 (S) Operand must be a modifiable 
lvalue.

Which means that this macro

    CMAP_PRIV(pCmap) = pallete;

can not be compiled. This or a similar macro is used at several places. 
The macro looks like

#define CMAP_PRIV(pCmap) \
     ((CGDirectPaletteRef) 
(pCmap)->devPrivates[darwinCmapPrivateIndex].ptr)

I don't see wrong code. So I think the error is at a deeper place. But 
I don't know where this devPrivates[].ptr is being built.

So I would like to get some help from the original hw/darwin developers.

Thanks

Regards

Tukaram