[SR-14109] Not possible to build cross-platform Swift libraries with optional assembly code

[Lukasa]

Previous ID	SR-14109
Radar	rdar://problem/73742495
Original Reporter	@Lukasa
Type	Bug

Additional Detail from JIRA

Votes	1
Component/s	Package Manager
Labels	Bug
Assignee	None
Priority	Medium

md5: 01915d10b315e2ff379d4577b7597796

Issue Description:

Derived from SwiftNIO SSL issue #251.

Some Apple platforms require app submission using bitcode, a non-final representation of the binary artefact. Bitcode submissions have a number of constraints that don't apply to binary submission. One of these is that they must not contain any raw assembly code, either as blocks or as complete files. Importantly, the compiler will reject the mere presence of any .s/.S files in the build tree, even if those files are empty and contribute no object data to the build.

SwiftPM supports mixed C/assembly targets, and SwiftNIO SSL uses this support. This mostly works great, unless someone wants to ship a watchOS app using SwiftNIO SSL (a supported platform). Here the mixed C/assembly files cause a fatal build error.

We need a way to exclude assembly files using SwiftPM depending on the deployment target that does not rely on kicking those files out to a separate target.

[Lukasa]

@swift-ci create

[swift-ci]

Comment by David E. Weekly (JIRA)

AFAICT this being unresolved means that watchOS apps can't use gRPC, because the gRPC library requires swift-nio-ssl.

[asauray]

any updates on this issue ?

[neonichu]

I'm guessing this may become irrelevant with the deprecation of bitcode?

[Lukasa]

Yes, that seems likely to me.