xalloc is now called with a size_t argument. If the argument type is silently changed to an idx_t, existing code which calls the new xalloc still with a size_t argument will trigger a compiler warning under GCC's -Wsign-conversion.
Fixing existing code isn't easy because the sizeof operator returns a size_t, which somehow would have to be converted to an idx_t without triggering any compiler warnings.
The coexistence of size_t and idx_t is problematic. If we want to drop size_t somewhere, we have to drop it everywhere it seems. This includes providing a signed sizeof operator and modules like flexmember may have to revisited as well.
Marc