nix/src/libstore/build/hook-instance.cc

#include "globals.hh"
#include "hook-instance.hh"

namespace nix {

HookInstance::HookInstance()
{
    debug("starting build hook '%s'", settings.buildHook);

    /* Create a pipe to get the output of the child. */
    fromHook.create();

    /* Create the communication pipes. */
    toHook.create();

    /* Create a pipe to get the output of the builder. */
    builderOut.create();

    /* Fork the hook. */
    pid = startProcess([&]() {

        commonChildInit(fromHook);

        if (chdir("/") == -1) throw SysError("changing into /");

        /* Dup the communication pipes. */
        if (dup2(toHook.readSide.get(), STDIN_FILENO) == -1)
            throw SysError("dupping to-hook read side");

        /* Use fd 4 for the builder's stdout/stderr. */
        if (dup2(builderOut.writeSide.get(), 4) == -1)
            throw SysError("dupping builder's stdout/stderr");

        /* Hack: pass the read side of that fd to allow build-remote
           to read SSH error messages. */
        if (dup2(builderOut.readSide.get(), 5) == -1)
            throw SysError("dupping builder's stdout/stderr");

        Strings args = {
            std::string(baseNameOf(settings.buildHook.get())),
            std::to_string(verbosity),
        };

        execv(settings.buildHook.get().c_str(), stringsToCharPtrs(args).data());

        throw SysError("executing '%s'", settings.buildHook);
    });

    pid.setSeparatePG(true);
    fromHook.writeSide = -1;
    toHook.readSide = -1;

    sink = FdSink(toHook.writeSide.get());
    std::map<std::string, Config::SettingInfo> settings;
    globalConfig.getSettings(settings);
    for (auto & setting : settings)
        sink << 1 << setting.first << setting.second.value;
    sink << 0;
}


HookInstance::~HookInstance()
{
    try {
        toHook.writeSide = -1;
        if (pid != -1) pid.kill();
    } catch (...) {
        ignoreException();
    }
}

}