xmake-swift

Building Swift with Xmake

Xmake builds Swift through swiftc and integrates with Xcode on Apple platforms. Use it when you want the same xmake.lua to drive a project that mixes Swift with C/C++/Objective-C.

1. Minimal project

xmake create -l swift -t console hello
cd hello
xmake run

add_rules("mode.debug", "mode.release")

target("hello")
    set_kind("binary")
    add_files("src/*.swift")

2. Target kinds

target("app")       set_kind("binary")
target("mylib")     set_kind("static")
target("mydyn")     set_kind("shared")

3. Swift ↔ C++/Objective-C interop (v3.0.5+)

Xmake supports automatic Swift-interop C++ header generation through the swift.interop target value.

Call Swift from C++

target("myswift")
    set_kind("static")
    add_files("src/*.swift")
    set_values("swift.interop", "cxx")                 -- or "objc"
    set_values("swift.modulename", "MySwift")          -- C++ namespace name

target("app")
    set_kind("binary")
    add_files("src/main.cpp")
    add_deps("myswift")
    set_languages("c++17")

Xmake generates a C++ header with #include "MySwift-Swift.h" style, exposing Swift types under MySwift:: namespace.

Interop modes

• "objc" — Objective-C interop (classic, works since early Swift)
• "cxx" — C++ interop (Swift 5.9+ required)

Resolving duplicate main

When both Swift and C++ have a main, Swift's usually wins. Force the C++ one:

set_values("swift.interop.cxxmain", true)

4. Apple platforms

xmake f -p macosx  -a arm64
xmake f -p iphoneos -a arm64
xmake f -p iphonesimulator -a arm64
xmake

Xmake picks up Xcode automatically. Pin SDK version with --xcode_sdkver=16.2, deployment target with --target_minver=12.0.

5. Flags

target("app")
    add_files("src/*.swift")
    add_scflags("-O")                  -- passed to swiftc
    add_ldflags("-Wl,-dead_strip")

add_scflags = Swift compiler flags.

6. Toolchain

xmake f --toolchain=swift
xmake f --toolchain=swift --sdk=/Applications/Xcode.app/Contents/Developer

On Linux, install swift from swift.org and point --sdk at the install root.

Pitfalls

• C++ interop needs Swift 5.9+. Older Xcode won't compile swift.interop = "cxx" projects.
• Swift modules are per-target. Each target("...") that has .swift files produces a module; don't split Swift sources across unrelated targets without thinking about the module boundary.
• Forgetting set_values("swift.modulename", ...). Interop uses the module name as the C++ namespace — default is the target name, and if that has hyphens you'll get invalid C++.
• Mixing Swift and Objective-C in one target without swift.interop = "objc". Add a bridging header manually, or use the interop value.

When to branch out

• Apple-platform cross-compile (iOS, tvOS, watchOS) → xmake-cross-compilation
• Target basics → xmake-targets
• C++ side configuration → xmake-cxx-modules (if using C++20 modules)