I suppose that how safe a grammar is to parse depends on whether or not there are language constructs that can generate exponential growths of memory usage, how

I suppose that how safe a grammar is to parse depends on whether or not there are language constructs that can generate exponential growths of memory usage, how much memory you have available for the task, and whether or not it can even be parsed at all. It seems like the only way to totally secure an automated system against this kind of attack is to have a limit on parser memory usage and CPU cycles, and reject input when the parser breaks any of these limits.