Rust’s scope-related rules are often highly convenient in their ability to ensure that things drop out of memory at appropriate times without the need for manual intervention. (And, occasionally, highly inconvenient in their ability to ensure that things drop out of memory while you’re still trying to use them; but I’m running afoul of that increasingly rarely as I improve my intuition for the language.) Memory is released when things fall out of scope, and there’s rarely any need to get more complicated than that.

Still, once in a while, manual intervention remains valuable; for example, when a resource has locked a file or a mutex, done everything it needs to do therewith, but not yet fallen out of scope in such a way as to unlock said file-or-mutex for the next resource that might want to access it.

When circumstances such as those arise, Rust has a convenient function to force a resource out of scope early. This function is drop. It is highly convenient (for those cases where the even-more-convenient scope rules fail to take precedence), and I’m glad to have discovered it.

Tags: Rust