On 02/19/2015 03:09 PM, Jakub Jelinek wrote:
>
> If you have hw where NULL is mapped and you know your code violates the
> C/C++ standards by placing objects at that address, simply do use
> the option that is designed for that purpose.

As I pointed out earlier, though, that won't help you if your program 
(perhaps implicitly) uses library code that's been built without the 
magic option.

I thought that declaring an object explicitly placed at address 0 as 
"volatile" ought to be sufficient to prevent writes to it from being 
optimized away and replaced with traps, but alas, that is not the case. 
  Also, a structure copy to such a volatile object is implicitly 
invoking the regular memcpy function without complaining about casting 
away volatile-ness, as an explicit call would do.  I've attached a 
couple quick test cases and .s output from arm-none-eabi-gcc -O2, using 
a mainline build from last night.

-Sandra