Function runAppImage

src/ui/main.cpp:38–95

Runs an AppImage. Returns suitable exit code for main application.

// Runs an AppImage. Returns suitable exit code for main application.
int runAppImage(const QString& pathToAppImage, unsigned long argc, char** argv) {
    // needs to be converted to std::string to be able to use c_str()
    // when using QString and then .toStdString().c_str(), the std::string instance will be an rvalue, and the
    // pointer returned by c_str() will be invalid
    auto fullPathToAppImage = QFileInfo(pathToAppImage).absoluteFilePath();

    auto type = appimage_get_type(fullPathToAppImage.toStdString().c_str(), false);
    if (type < 1 || type > 3) {
        displayError(QObject::tr("AppImageLauncher does not support type %1 AppImages at the moment.").arg(type));
        return 1;
    }

    // first of all, chmod +x the AppImage registerFile
    // be happy the registerFile is executable already
    if (!makeExecutable(fullPathToAppImage)) {
        displayError(QObject::tr("Could not make AppImage executable: %1").arg(fullPathToAppImage));
        return 1;
    }

    // suppress desktop integration script etc.
    setenv("DESKTOPINTEGRATION", "AppImageLauncher", true);

    auto makeVectorBuffer = [](const std::string& str) {
        std::vector<char> strBuffer(str.size() + 1, '\0');
        strncpy(strBuffer.data(), str.c_str(), str.size());
        return strBuffer;
    };

    // calculate buffer to bypass binary
    std::string pathToBinfmtBypassLauncher = privateLibDirPath("binfmt-bypass").toStdString() + "/binfmt-bypass";

    // create new args array for exec()d process
    std::vector<char*> args;

    // first argument is the path to our launcher
    auto pathToBinfmtBypassLauncherBuffer = makeVectorBuffer(pathToBinfmtBypassLauncher);
    args.push_back(pathToBinfmtBypassLauncherBuffer.data());

    // first argument is consumed by the bypass launcher
    // the reason we launch the bypass launcher as a new process to save RAM (we have to launch the actual AppImage
    // as a subprocess, and the launcher executable has a much lower memory footprint)
    auto pathToAppImageBuffer = makeVectorBuffer(pathToAppImage.toStdString());
    args.push_back(pathToAppImageBuffer.data());

    // copy arguments
    for (unsigned long i = 1; i < argc; i++) {
        args.push_back(argv[i]);
    }

    // args need to be null terminated
    args.push_back(nullptr);

    execv(pathToBinfmtBypassLauncher.c_str(), args.data());

    const auto& error = errno;
    std::cerr << QObject::tr("execv() failed: %1").arg(strerror(error)).toStdString() << std::endl;
    return 1;
}