build-seastar.sh

#!/usr/bin/env bash

set -euo pipefail

export DEBIAN_FRONTEND=noninteractive

# Build Seastar framework from source
# This script clones the Seastar repository, installs dependencies,
# configures the build with required libraries, and compiles the project.

readonly SEASTAR_REPO="https://github.com/scylladb/seastar"
readonly SEASTAR_DIR="seastar"
readonly BUILD_DIR="build/release"
readonly MODE="${MODE:-}"
readonly USE_LLVM="${USE_LLVM:-}"

# Global variable to track LLVM version if installed
LLVM_VERSION=""

is_ubuntu_2204() {
    [[ -f /etc/os-release ]] || return 1
    source /etc/os-release
    [[ "${ID}" == "ubuntu" && "${VERSION_ID}" == "22.04" ]]
}

install_llvm() {
    # Determine if we should install LLVM and which version
    if is_ubuntu_2204; then
        # Ubuntu 22.04 always uses LLVM (default to 20 if not specified)
        LLVM_VERSION="${USE_LLVM:-20}"
    elif [[ -n "${USE_LLVM}" ]]; then
        # Other systems only if explicitly requested
        LLVM_VERSION="${USE_LLVM}"
    else
        return 0
    fi

    local llvm_version="${LLVM_VERSION}"

    # Check if clang++ is already installed
    if command -v "clang++-${llvm_version}" &>/dev/null; then
        echo "LLVM ${llvm_version} (clang++-${llvm_version}) is already installed. Skipping installation."
        return 0
    fi

    echo "Installing LLVM ${llvm_version}..."

    if is_ubuntu_2204; then
        # Use llvm.sh on Ubuntu 22.04
        local llvm_script="/tmp/llvm.sh"

        # Download llvm.sh if not already present
        if [[ ! -f "${llvm_script}" ]]; then
            wget -O "${llvm_script}" https://apt.llvm.org/llvm.sh
            chmod +x "${llvm_script}"
        fi

        sudo "${llvm_script}" "${llvm_version}"
    else
        # On other systems, try to install via package manager
        echo "Not on Ubuntu 22.04, attempting to install LLVM ${llvm_version} via system package manager..."
        if command -v apt-get &>/dev/null; then
            sudo apt-get update
            sudo apt-get install -y "llvm-${llvm_version}" "clang-${llvm_version}"
        elif command -v dnf &>/dev/null; then
            sudo dnf install -y "llvm${llvm_version}" "clang${llvm_version}"
        elif command -v yum &>/dev/null; then
            sudo yum install -y "llvm${llvm_version}" "clang${llvm_version}"
        else
            echo "Warning: No supported package manager found. Please install LLVM ${llvm_version} manually."
            return 1
        fi
    fi

    echo "LLVM ${llvm_version} installed successfully."
}

main() {
    echo "Starting Seastar build process..."

    # Install LLVM if requested
    install_llvm

    # Clone the repository if it doesn't exist
    if [[ -d "${SEASTAR_DIR}" ]]; then
        echo "Directory ${SEASTAR_DIR} already exists. Skipping clone."
        cd "${SEASTAR_DIR}"
    else
        echo "Cloning Seastar repository..."
        git clone "${SEASTAR_REPO}"
        cd "${SEASTAR_DIR}"
    fi

    # Install system dependencies
    echo "Installing dependencies (requires sudo)..."
    sudo ./install-dependencies.sh

    # Configure the build
    local configure_args=(--cook fmt --cook GnuTLS)
    if [[ -n "${MODE}" ]]; then
        configure_args+=(--mode "${MODE}")
    fi
    if [[ -n "${LLVM_VERSION}" ]]; then
        configure_args+=(--compiler "clang++-${LLVM_VERSION}")
    fi
    if is_ubuntu_2204; then
        configure_args+=(--c++-standard=20)
    fi

    # Print configuration message
    local config_msg="Configuring build with fmt and GnuTLS"
    [[ -n "${MODE}" ]] && config_msg+=" (mode: ${MODE})"
    [[ -n "${LLVM_VERSION}" ]] && config_msg+=" (compiler: clang++-${LLVM_VERSION})"
    echo "${config_msg}..."

    ./configure.py "${configure_args[@]}"

    # Build the project
    echo "Building Seastar with ninja..."
    cd "${BUILD_DIR}"
    ninja

    echo "Build completed successfully!"
}

main "$@"