# Swift Runtime

**URL:** <https://forums.swift.org/t/swift-runtime/82856>\
**Category:** Using Swift\
**Tags:** runtime, binary-framework\
**Created:** [October 25, 2025, 1:45am UTC](https://forums.swift.org/t/swift-runtime/82856 "2025-10-25T01:45:00Z")\
**Posts on this page:** 1\
**Showing post:** 5

<div class="post-metadata">

**Author:** ![Finagolfin](https://sea2.discourse-cdn.com/swift/user_avatar/forums.swift.org/finagolfin/32/34388_2.png) [@Finagolfin](https://forums.swift.org/u/Finagolfin)\
**Post date:** [October 28, 2025, 2:43pm UTC](https://forums.swift.org/t/swift-runtime/82856/5 "2025-10-28T14:43:41Z")

</div>

> [@realmtai](#):
>
> How does the swift compiled code calls into the native C code?

Swift has great support for interfacing with C and Objective-C. The Swift compiler [ingests any C headers you provide and will generate the right machine code to call those C functions](https://github.com/swiftlang/swift/blob/main/docs/HowSwiftImportsCAPIs.md), no need for you to write any manual bindings like in other languages. It is not foolproof- it can only decipher constants from the C preprocessor, for example- but works very well.

Right now, there is even work under way to go the other way more easily, ie [write your code in Swift and call it from C](https://forums.swift.org/t/accepted-se-0495-c-compatible-functions-and-enums/82833). 😎

> [@realmtai](#):
>
> Also, how does runtime feature like ARC and async/await work, if there are no runtime?

Oh, there is definitely a Swift runtime, you can [find its source here](https://github.com/swiftlang/swift/tree/main/stdlib). It is written in a mix of Swift and C++. I was merely pointing out that it builds on top of your OS C library on most platforms, except maybe less for [the embedded targets](https://www.swift.org/blog/embedded-swift-examples/).

> [@realmtai](#):
>
> Is there a good blog/article for this? I'm looking in writing one, if there isn't one.

Not that I know of, but difficult to keep track of all the Swift articles and blogs out there. 😉 Use your favorite search engine and see what you find.

---

_[View the full topic](https://forums.swift.org/t/swift-runtime/82856)._