# What does \`unsafe\` mean?

**URL:** <https://internals.rust-lang.org/t/what-does-unsafe-mean/6696>\
**Category:** Unsafe Code Guidelines\
**Created:** [February 2, 2018, 9:26pm UTC](https://internals.rust-lang.org/t/what-does-unsafe-mean/6696 "2018-02-02T21:26:20Z")\
**Posts on this page:** 1\
**Showing post:** 33

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**Author:** ![scottmcm](https://sea2.discourse-cdn.com/flex002/user_avatar/internals.rust-lang.org/scottmcm/32/2355_2.png) [@scottmcm](https://internals.rust-lang.org/u/scottmcm)\
**Post date:** [April 29, 2018, 1:05am UTC](https://internals.rust-lang.org/t/what-does-unsafe-mean/6696/33 "2018-04-29T01:05:52Z")

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I wouldn’t say I know precisely what an “effect” means theoretically, but I noticed something different between the “async” and “try” effects and the “unsafe” one: for the former two, you can call a function that returns `impl Future` or `Result` then “apply the effect” later with `await` or `?`, but one cannot call something `unsafe` from something safe then “apply the unsafety” later.

Is that a meaningful difference?

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