Issue 120: move local variables out of block to prevent them going out of scope. arg3 points to length and if memcached_fetch_rvalue fails to set it, it will point to a random value in the stack, which ruby_str_new will try to allocate with unpredictable results, if memcached_fetch_rvalue does not set it
Merge pull request #121 from plerohellec/master

Make sure memcached_fetch arguments have default values