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Phase 17. Static Linux SDK single binary

FieldValue
MEPMEP-49 §Phases · Phase 17
StatusLANDED
Started2026-05-28 13:40 (GMT+7)
Landed2026-05-28 13:40 (GMT+7)
Tracking issue—
Tracking PR—

Gate​

TestPhase17StaticLinux: validates Swift source generation for static Linux targets. Actual swift build --swift-sdk cross-compilation is skipped when the Static Linux SDK is not installed (StaticLinuxSDKAvailable returns false). 3 fixtures.

Goal-alignment audit​

The static Linux binary is Mochi's zero-dependency server deployment story. Phase 17 ships the SDK availability check, the SDK triple constants, and the TargetLinuxStaticX64/TargetLinuxStaticArm64 build targets in the Driver. The actual ldd gate (verifying "not a dynamic executable") and Alpine container test are deferred to a sub-phase that requires a Linux CI runner with the SDK installed.

Sub-phases​

#ScopeStatusCommit
17.0SDKTripleX64, SDKTripleArm64 constants; StaticLinuxSDKAvailable(triple) helperLANDEDmep/0049-phase-17
17.1TargetLinuxStaticX64, TargetLinuxStaticArm64 in Driver.Build; --swift-sdk flag injectionLANDEDmep/0049-phase-17
17.2ldd gate: verify binary is statically linked on linux-x64DEFERRED—
17.3Alpine Linux Docker container cold-start testDEFERRED—
17.4Binary size measurement and -Osize flagDEFERRED—

Sub-phase 17.0 -- SDK availability​

Decisions made (17.0)​

SDKTripleX64 = "x86_64-swift-linux-musl" and SDKTripleArm64 = "aarch64-swift-linux-musl": the Swift SDK triple identifiers used with --swift-sdk.

StaticLinuxSDKAvailable(triple string) bool: runs swift sdk list and checks whether the output contains the given triple. Returns false if swift is not on PATH.

func StaticLinuxSDKAvailable(triple string) bool {
    out, err := exec.Command("swift", "sdk", "list").Output()
    if err != nil { return false }
    return strings.Contains(string(out), triple)
}

The gate test calls StaticLinuxSDKAvailable(SDKTripleX64) and calls t.Skip when the SDK is not installed, so the test always passes in CI without the SDK.

Sub-phase 17.1 -- Static build targets​

Decisions made (17.1)​

TargetLinuxStaticX64 and TargetLinuxStaticArm64: new target constants in build.go. When selected, Driver.Build passes --swift-sdk <triple> and --static-swift-stdlib to swift build.

Cross-compilation from macOS: supported when the Static Linux SDK is installed. The build output goes to .build/<triple>/release/<binary>.

Files changed​

FilePurpose
transpiler3/swift/build/sdk.goSDKTripleX64, SDKTripleArm64, StaticLinuxSDKAvailable
transpiler3/swift/build/build.goTargetLinuxStaticX64, TargetLinuxStaticArm64; --swift-sdk flag injection
transpiler3/swift/build/phase17_test.goTestPhase17StaticLinux: 3 fixtures; skips if SDK absent
tests/transpiler3/swift/fixtures/phase17-static-linux/3 fixture directories

Test set​

  • TestPhase17StaticLinux -- 3 fixtures: static_func, static_hello, static_int. Test skips when StaticLinuxSDKAvailable(SDKTripleX64) returns false.

Deferred work​

  • ldd gate: assert binary output is "not a dynamic executable" on a linux-x64 runner. Deferred to Phase 17.2.
  • Alpine Linux Docker container test (docker run alpine:3.20 /app/MochiOut). Deferred to Phase 17.3.
  • Binary size measurement; -Osize flag support. Deferred to Phase 17.4.
  • strip -S + optional upx --lzma compression. Deferred.
  • Windows cross-compilation from macOS. Deferred.
  • WASI (WebAssembly System Interface). Out of v1 scope.