libcruft-util/cruft/util/exe_linux.cpp

/*
 * This Source Code Form is subject to the terms of the Mozilla Public
 * License, v. 2.0. If a copy of the MPL was not distributed with this
 * file, You can obtain one at http://mozilla.org/MPL/2.0/.
 *
 * Copyright 2010-2016 Danny Robson <danny@nerdcruft.net>
 */

#include "exe.hpp"

#include "cast.hpp"
#include "posix/except.hpp"

#include <vector>
#include <filesystem>

#include <unistd.h>


///////////////////////////////////////////////////////////////////////////////
std::filesystem::path
cruft::image_path (void)
{
    static const char PROC_SELF[] = "/proc/self/exe";

    // We can't use lstat to check the size of the link in proc, as Linux
    // will return 0 for most entries under proc. Instead we've got to
    // iterate for a correct size.
    std::vector<char> resolved (256);

retry:
    const auto written = readlink (PROC_SELF, resolved.data (), resolved.size ());
    if (written < 0)
        posix::error::throw_code ();

    if (cruft::cast::sign <size_t> (written) == resolved.size ()) {
        resolved.resize (resolved.size () * 2);
        goto retry;
    }

    return std::filesystem::path (resolved.data (), resolved.data () + written);
}