Swift

Overview

Swift is Apple's modern programming language for building safe, fast, and expressive code. Runner Codes provides Swift 5.10.1 runtime for Linux.

Specifications

Property	Value
Base OS	Debian Bookworm
Version	Swift 5.10.1
Rootfs Size	4 GB
Execution	Interpreted (swift)
File Extension	`.swift`
Run Command	`swift script.swift`
Execution Time	~2.9s

Infrastructure

warning

Swift requires manual installation because:

Debian's "swift" package is OpenStack Swift (object storage), not Apple Swift
Swift binaries use AVX2/AVX-512 instructions - requires T2CL CPU template in Firecracker
Large toolchain (~1.9GB) requires 4GB rootfs

Manual Installation Steps

1. Create 4GB Rootfs Image
sudo dd if=/dev/zero of=/srv/firecracker/images/rootfs-swift.ext4 bs=1M count=4096 status=progress
sudo mkfs.ext4 /srv/firecracker/images/rootfs-swift.ext4
sudo mkdir -p /mnt/swift
sudo mount /srv/firecracker/images/rootfs-swift.ext4 /mnt/swift

2. Install Debian Base System
sudo debootstrap --variant=minbase bookworm /mnt/swift http://deb.debian.org/debian

3. Install Swift Dependencies
sudo chroot /mnt/swift apt-get update
sudo chroot /mnt/swift apt-get install -y --no-install-recommends \
    binutils \
    libc6-dev \
    libcurl4-openssl-dev \
    libedit-dev \
    libncurses-dev \
    libsqlite3-dev \
    libxml2-dev \
    libicu-dev \
    ca-certificates \
    zlib1g

4. Download Swift 5.10.1 from swift.org (NOT from Debian repos!)
cd /tmp
wget https://download.swift.org/swift-5.10.1-release/ubuntu2204/swift-5.10.1-RELEASE/swift-5.10.1-RELEASE-ubuntu22.04.tar.gz
tar -xzf swift-5.10.1-RELEASE-ubuntu22.04.tar.gz

5. Copy Swift to Rootfs
sudo cp -r /tmp/swift-5.10.1-RELEASE-ubuntu22.04/usr/* /mnt/swift/usr/

6. Configure Dynamic Linker for Swift Libraries
echo '/usr/lib/swift/linux
/usr/lib/swift/host
/usr/lib/swift/clang/lib
/usr/lib/swift' | sudo tee /mnt/swift/etc/ld.so.conf.d/swift.conf
sudo chroot /mnt/swift ldconfig

7. Copy infra.operator Binary
sudo cp /usr/local/bin/infra.operator /mnt/swift/usr/local/bin/
sudo chmod +x /mnt/swift/usr/local/bin/infra.operator

8. Unmount and Create Snapshot
sudo sync
sudo umount /mnt/swift
sudo infra.operator snapshot create --lang swift --mem 1024 --vcpus 1

9. Upload to S3
sudo infra.operator snapshot upload --lang swift --bucket runner-codes
aws s3 cp /srv/firecracker/images/rootfs-swift.ext4 s3://runner-codes/rootfs/swift/

10. Test Execution
sudo infra.operator host --lang swift --code 'print("Hello from Swift")' \
    --mem 1024 --vcpus 1 --snapshot --cache-dir /dev/shm/snapshots

CPU Template Requirement

note

Swift binaries are compiled with AVX2/AVX-512 instructions. Firecracker must use the T2CL CPU template to expose these instructions to the guest VM. This was configured in pkg/host/firecracker.go:

Function
// ConfigureMachine sets the machine configuration
func (fc *FirecrackerClient) ConfigureMachine(vcpus, memMiB int) error {
    config := MachineConfig{
        VCPUCount:   vcpus,
        MemSizeMiB:  memMiB,
        SMT:         false,
        CPUTemplate: "T2CL", // Expose Cascade Lake features (AVX, AVX2, AVX-512) to guest
    }
    return fc.putJSON("/machine-config", config)
}

Troubleshooting

Issue	Cause	Solution
`Illegal instruction`	Missing CPU features	Use T2CL CPU template
`libSwiftCore.so not found`	Missing library path	Configure `/etc/ld.so.conf.d/swift.conf`
`No space left on device`	Rootfs too small	Use 4GB rootfs (Swift needs ~2.5GB)
`swift: command not found`	Wrong package	Use swift.org binaries, not Debian's OpenStack Swift

Examples

Hello World

Request
{
  "trace_id": "swift-hello-001",
  "lang": "swift",
  "code": "print(\"Hello from Swift!\")",
  "timeout": 30
}

Response
{
  "trace_id": "swift-hello-001",
  "stdout": "Hello from Swift!\n",
  "stderr": "",
  "exit_code": 0
}

Variables and Types

Request
{
  "trace_id": "swift-vars-001",
  "lang": "swift",
  "code": "let name = \"Swift\"\nlet version = 5.10\nvar count = 0\ncount += 1\nprint(\"Language: \\(name)\")\nprint(\"Version: \\(version)\")\nprint(\"Count: \\(count)\")",
  "timeout": 30
}

Response
{
  "trace_id": "swift-vars-001",
  "stdout": "Language: Swift\nVersion: 5.1\nCount: 1\n",
  "stderr": "",
  "exit_code": 0
}

Collections

Request
{
  "trace_id": "swift-coll-001",
  "lang": "swift",
  "code": "let numbers = [1, 2, 3, 4, 5]\nlet squares = numbers.map { $0 * $0 }\nlet sum = squares.reduce(0, +)\n\nprint(\"Numbers: \\(numbers)\")\nprint(\"Squares: \\(squares)\")\nprint(\"Sum: \\(sum)\")",
  "timeout": 30
}

Response
{
  "trace_id": "swift-coll-001",
  "stdout": "Numbers: [1, 2, 3, 4, 5]\nSquares: [1, 4, 9, 16, 25]\nSum: 55\n",
  "stderr": "",
  "exit_code": 0
}

Optionals and Nil Safety

Request
{
  "trace_id": "swift-opt-001",
  "lang": "swift",
  "code": "var name: String? = nil\nprint(name ?? \"Name is nil\")\n\nname = \"Alice\"\nif let unwrapped = name {\n    print(\"Name is \\(unwrapped)\")\n}",
  "timeout": 30
}

Response
{
  "trace_id": "swift-opt-001",
  "stdout": "Name is nil\nName is Alice\n",
  "stderr": "",
  "exit_code": 0
}

Structs and Methods

Request
{
  "trace_id": "swift-struct-001",
  "lang": "swift",
  "code": "struct Person {\n    let name: String\n    let age: Int\n    \n    func greet() -> String {\n        return \"Hello, I'm \\(name) and I'm \\(age) years old\"\n    }\n}\n\nlet alice = Person(name: \"Alice\", age: 30)\nprint(alice.greet())",
  "timeout": 30
}

Response
{
  "trace_id": "swift-struct-001",
  "stdout": "Hello, I'm Alice and I'm 30 years old\n",
  "stderr": "",
  "exit_code": 0
}

Closures and Higher-Order Functions

Request
{
  "trace_id": "swift-closure-001",
  "lang": "swift",
  "code": "let numbers = [1, 2, 3, 4, 5, 6, 7, 8, 9, 10]\n\nlet evens = numbers.filter { $0 % 2 == 0 }\nlet doubled = numbers.map { $0 * 2 }\nlet sum = numbers.reduce(0) { $0 + $1 }\n\nprint(\"Evens: \\(evens)\")\nprint(\"Doubled: \\(doubled)\")\nprint(\"Sum: \\(sum)\")",
  "timeout": 30
}

Response
{
  "trace_id": "swift-closure-001",
  "stdout": "Evens: [2, 4, 6, 8, 10]\nDoubled: [2, 4, 6, 8, 10, 12, 14, 16, 18, 20]\nSum: 55\n",
  "stderr": "",
  "exit_code": 0
}

Limitations

warning

The Swift environment has the following limitations:

Large rootfs: Swift toolchain requires ~4GB
No external packages: Only Swift standard library
Memory limit: 1024 MiB recommended
Interpreted mode: Uses swift interpreter (not compiled)
No Foundation extras: Network operations will fail

Best Practices

Handle optionals safely — Always use optional binding (if let, guard let) to safely unwrap optionals.
Prefer structs — For simple data types, prefer structs for value semantics and performance.
Use standard library — Only Swift standard library is available.
Account for compilation — Set timeout to at least 60 seconds for compilation time.

Overview​

Specifications​

Infrastructure​

Manual Installation Steps​

CPU Template Requirement​

Troubleshooting​

Examples​

Hello World​

Variables and Types​

Collections​

Optionals and Nil Safety​

Structs and Methods​

Closures and Higher-Order Functions​

Limitations​

Best Practices​