Question

I’ve written a simple Ruby C extension. A method expects the second parameter to be a string-ish VALUE.

VALUE method_foo(VALUE self, VALUE key) {

  puts(RSTRING(key)->ptr);

  return key;
}

Its very easy to cause a segmentation fault by passing an integer rather than a string. How should I detect this and either prevent or recover in the C method?

Answer 1

You should look into calling Check_Type (key, T_STRING) (if you want an exception raised) or using TYPE (key) to check it manually (if you want to do something other than raise an exception).

Alternatively, you could simply state that method_foo expects a string and leave it up to the caller to handle. Your API is, after all, a contract between caller and callee and, if the caller breaks the rules, it’s a perfectly valid response to crash.

I probably wouldn’t do that since I prefer robust software but there’s a school of thought that people shouldn’t always necessarily be protected from their own foolishness. It only encourages them to stay foolish 🙂