Issue was, in case of using such stack within a structure, the '_' underscore
would be added in front of struct variable
(e.g. `my_struct.my_stack` would lead to (try to) using `_my_struct.my_var_pool` ...).
Now underscore is appended to var names, ugly but working.
Note did not touch to the alloca variants of those macros, since in this case enforcing
a pure local use is best I think.