Overwriting constant strings is a very real error and should be fixed. Code like this would crash in Windows, for example.
These warnings do not mean overwriting, simply passing a string constant to a function which takes char *; a potential, not necessarily a real error. It is allowed in C, not in C++.
Of course, it would be good to check all warnings, some can be bugs. Not all useful warnings are included in -Wall. It may be worth to activate more.
But warnings should not deter from adoption of GCC 4.4.
So as I said, ReactOS need an in-tree version of libgcc with proper support for __enable_execute_stack for kernel-mode.
It is not needed in user-mode, too. Nested functions are only used by PSEH2, and it works well without __enable_execute_stack()