You call the function
yypstate_new to create a new parser instance.
This function is available if either the ‘%define api.push-pull push’ or
‘%define api.push-pull both’ declaration is used.
See A Push Parser.
The function will return a valid parser instance if there was memory available or 0 if no memory was available. In impure mode, it will also return 0 if a parser instance is currently allocated.