[Pitch] Formalize @cdecl
#2813
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[Pitch] Formalize @cdecl
#2813
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| > Note: The attribute `@objc` is already accepted on enums that will be usable from `@objc` global function signatures but not from `@cdecl` functions. | ||
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| Extend support for the `@implementation` attribute, introduced in [SE-0436](https://github.com/swiftlang/swift-evolution/blob/main/proposals/0436-objc-implementation.md), to global functions marked with either `@cdecl` or `@objc`. Type-checking ensures the C declaration matches the definition in Swift. Functions marks as `@implementation` are not be printed in the compatibility header. |
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| > Note: This proposal aims to formalize, clean up and extend the long experimental `@_cdecl`. While experimental this attribute has been widely in use so we will refer to it as needed for clarity in this document. | ||
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| ## Motivation |
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This wasn't super clear to me, I think that you should lead with the fact that there are two ways Swift can support interop:
- by having the compiler emit a header file that contains C declarations for Swift symbols
- by implementing functions that are declared in a user-written header
and that @cdecl/@objc are for the former and @implementation for the latter.
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Pitch to formalize
@cdeclto identify global functions as callable from C code, and supporting features.