clib2 Code

request to allocate 0 bytes as an error, returning NULL. They all
return a pointer sized memory chunk (= four bytes) initialized to
NULL (= 0) instead.

- The alloca() implementation which allocates memory from the system
rather than the local stack frame is thread-safe now. It also
interacts with the realloc(), calloc(), free() and malloc() functions
in that the alloca() cleanup routine is called once alloca() has
done its job. If all the memory allocated through alloca() has been
released no further calls to the cleanup function will be made.

- In the thread-safe library, realloc() permitted two different overlapping
calls to succeed in trying to reallocate the same chunk of memory due to
a race condition. Fixed.