-current build failure

[David Chisnall]

On 20 Jul 2012, at 17:33, Konstantin Belousov wrote:

> It is not related to dtrace at all, and indeed OFFSETOF_CURTHREAD is 0.
> This is a bug in clang, we compile our kernel in freestanding environment.

The copies of the C spec that I have do not differentiate between freestanding and hosted environments for the validity of dereferencing a pointer value of 0.  Doing so is undefined in all cases and any standards-compliant compiler is quite at liberty to eat your dog in such situations - it is explicitly not guaranteed to read the memory at linear address 0 (this is undefined for at least two reasons that I can think of from the C spec, and probably more).  

David