# Unable to use nested withUnsafePointer(to:\_:) with parameters marked \`borrowing\` **URL:** \ **Category:** Using Swift\ **Created:** [November 30, 2025, 6:05pm UTC](https://forums.swift.org/t/unable-to-use-nested-withunsafepointer-to-with-parameters-marked-borrowing/83474 "2025-11-30T18:05:56Z")\ **Posts on this page:** 1\ **Showing post:** 11
**Author:** ![ksluder](https://avatars.discourse-cdn.com/v4/letter/k/eada6e/32.png) [@ksluder](https://forums.swift.org/u/ksluder)\ **Post date:** [November 30, 2025, 6:56pm UTC](https://forums.swift.org/t/unable-to-use-nested-withunsafepointer-to-with-parameters-marked-borrowing/83474/11 "2025-11-30T18:56:15Z")
I don’t think `borrowing` would have the effect you think it would, because I don’t think `VkAllocationCallbacks` is going to be imported as `~Copyable`. So [per Joe’s explanation](https://forums.swift.org/t/what-do-borrowing-parameters-do-to-copyable-types/81217/2), the `borrowing` keyword won’t have any effect on the calling convention since `borrowing` is already the default for function arguments. > [@needlesslygrim](#): > > Passing both as arguments just shifts the error down: > […] > and trying to use `withoutActuallyEscaping(_:do:)` within the first onen doesn’t work: Can you share these errors, please? I did find [a related thread](https://forums.swift.org/t/borrowing-nested-withunsafepointer-cannot-be-captured-by-an-escaping-closure-since-it-is-a-borrowed-parameter/80210/8) from this summer where someone encountered the same issue with SDL, but there was no satisfying result. Unfortunately, I don’t think you can use `borrowing` to force your desired calling convention without making the type non-copyable, which can only be done by creating your own `~Copyable` wrapper type. --- _[View the full topic](https://forums.swift.org/t/unable-to-use-nested-withunsafepointer-to-with-parameters-marked-borrowing/83474)._