Stdlib Platform module/symbols not found in Embedded Mode

Development Embedded
1

Hi!

When I import Darwin and try to use a symbol defined in stdlib/public/Platform/Platform.swift, such as DarwinBoolean, Semaphore, or errno, that symbol is not found when compiling in embedded mode on a Mac. Why? Am I holding it wrong? I thought the stdlib had (partial) embedded support, at least that's what I inferred based on the @_unavailableInEmbedded attributes and #if !$Embedded around some of the code in said stdlib/public/Platform/Platform.swift. See CMakeLists in stdlib/public/Platform

Even funnier, when I compile in debug mode instead of release, the entire Darwin module cannot be imported (same goes for Darwin.C).

Is this a bug or do I need to pass in additional flags...?

Same issue, regardless whether SPM or xcode. I am using a current main snapshot with
-enable-experimental-feature Embedded -wmo, or, well, the SPM version of that (.enableExperimentalFeature("Embedded"), .unsafeFlags(["-wmo"]))

$ TOOLCHAINS=org.swift.62202503131a swift build -c release
[1/1] Planning build
Building for production...
path/to/main.swift:8:11: error: cannot find type 'Semaphore' in scope
 6 | import Darwin
 7 |
 8 | extension Semaphore {}
   |           `- error: cannot find type 'Semaphore' in scope
 9 | extension Darwin.Semaphore {}
10 |

path/to/main.swift:9:18: error: no type named 'Semaphore' in module 'Darwin'
 7 |
 8 | extension Semaphore {}
 9 | extension Darwin.Semaphore {}
   |                  `- error: no type named 'Semaphore' in module 'Darwin'

$ TOOLCHAINS=org.swift.62202503131a swift build
[1/1] Planning build
Building for debugging...
error: emit-module command failed with exit code 1 (use -v to see invocation)
<unknown>:0: error: module '_errno' cannot be imported in embedded Swift mode
<unknown>:0: error: module '_time' cannot be imported in embedded Swift mode
<unknown>:0: error: module '_signal' cannot be imported in embedded Swift mode
<unknown>:0: error: module 'sys_time' cannot be imported in embedded Swift mode
<unknown>:0: error: module '_stdio' cannot be imported in embedded Swift mode
<unknown>:0: error: module 'unistd' cannot be imported in embedded Swift mode
<unknown>:0: error: module '_math' cannot be imported in embedded Swift mode
path/to/main.swift:6:8: error: module 'Darwin' cannot be imported in embedded Swift mode
 4 | print("Hello, world! \(2) \(a)")
 5 |
 6 | import Darwin
   |        `- error: module 'Darwin' cannot be imported in embedded Swift mode
 7 |
 8 | extension Semaphore {}
<unknown>:0: error: module '_errno' cannot be imported in embedded Swift mode
<unknown>:0: error: module '_time' cannot be imported in embedded Swift mode
<unknown>:0: error: module '_signal' cannot be imported in embedded Swift mode
<unknown>:0: error: module 'sys_time' cannot be imported in embedded Swift mode
<unknown>:0: error: module '_stdio' cannot be imported in embedded Swift mode
<unknown>:0: error: module 'unistd' cannot be imported in embedded Swift mode
<unknown>:0: error: module '_math' cannot be imported in embedded Swift mode
path/to/main.swift:6:8: error: module 'Darwin' cannot be imported in embedded Swift mode
 4 | print("Hello, world! \(2) \(a)")
 5 |
 6 | import Darwin
   |        `- error: module 'Darwin' cannot be imported in embedded Swift mode
 7 |
 8 | extension Semaphore {}
2

I’m not sure why Darwin specific modules would be available in Embedded Swift which, I believe, is designed to be run on platforms where those modules would not be present. Is this wrong of me to assume?

3

What Xcode and SDK versions do you have?

Importing Darwin should give you at least the Darwin C module, as that's the only way to call standard C APIs on macOS/iOS. It's currently not possible to get the Darwin Swift overlay -- intentionally, at least for now. The reason is that the overlay is part of the SDK, and thus it's not Embedded Swift compatible. (The macOS/iOS SDK doesn't distribute any Embedded Swift modules.)

4

I was using Xcode 16.2 (16C5032a) with the bundled MacOSX15.2.sdk and
the 03-13a snapshot:

TOOLCHAINS=org.swift.62202503131a swift --version
Apple Swift version 6.2-dev (LLVM 8181ec46fb75248, Swift 27bac6952744072)
Target: arm64-apple-macosx15.0

Now I tried a current Xcode beta version (Xcode 16.3 beta 2 (16E5121h)) which comes with the MacOSX15.4.sdk (which, in turn, gets passed to swift build, right?), and that works (import Darwin[.C]), except for the overlay.

The overlay is the Platform.swift stuff, like errno, Semaphore, etc, isn't? At least that's my guess based on the error I get with the more recent .sdk when I try to access errno:

 80 | extern int * __error(void);
 81 | #define errno (*__error())
    |         `- note: macro 'errno' unavailable: structure not supported
 82 | __END_DECLS

Normally -- assuming I'm right about the overlay -- I'd expect errno to have a Swift getter:

// stdlib/public/Platform/Platform.swift
public var errno : Int32 {
  get {
    return _swift_stdlib_getErrno()
  }
  set(val) {
    return _swift_stdlib_setErrno(val)
  }
}

Plus, the nice argument labels for certain system calls like open aren't available -- suggesting this is the raw open function being imported, rather than the overlay.