Make macro expanded string immutable

The string is shared between different macro expand.
It is wrong to modify the string in place if the string
is used in a macro. Avoid overwriting the string in that
case.

Reported-by: Rasmus Villemoes <linux@rasmusvillemoes.dk>
Tested-by: Luc Van Oostenryck <luc.vanoostenryck@gmail.com>
Signed-off-by: Christopher Li <sparse@chrisli.org>
3 files changed