Class TraceResolverLinuxBase

backward.hpp:1252–1310

#ifdef BACKWARD_SYSTEM_LINUX

class TraceResolverLinuxBase : public TraceResolverImplBase {
public:
  TraceResolverLinuxBase()
      : argv0_(get_argv0()), exec_path_(read_symlink("/proc/self/exe")) {}
  std::string resolve_exec_path(Dl_info &symbol_info) const {
    // mutates symbol_info.dli_fname to be filename to open and returns filename
    // to display
    if (symbol_info.dli_fname == argv0_) {
      // dladdr returns argv[0] in dli_fname for symbols contained in
      // the main executable, which is not a valid path if the
      // executable was found by a search of the PATH environment
      // variable; In that case, we actually open /proc/self/exe, which
      // is always the actual executable (even if it was deleted/replaced!)
      // but display the path that /proc/self/exe links to.
      // However, this right away reduces probability of successful symbol
      // resolution, because libbfd may try to find *.debug files in the
      // same dir, in case symbols are stripped. As a result, it may try
      // to find a file /proc/self/<exe_name>.debug, which obviously does
      // not exist. /proc/self/exe is a last resort. First load attempt
      // should go for the original executable file path.
      symbol_info.dli_fname = "/proc/self/exe";
      return exec_path_;
    } else {
      return symbol_info.dli_fname;
    }
  }

private:
  std::string argv0_;
  std::string exec_path_;

  static std::string get_argv0() {
    std::string argv0;
    std::ifstream ifs("/proc/self/cmdline");
    std::getline(ifs, argv0, '\0');
    return argv0;
  }

  static std::string read_symlink(std::string const &symlink_path) {
    std::string path;
    path.resize(100);

    while (true) {
      ssize_t len =
          ::readlink(symlink_path.c_str(), &*path.begin(), path.size());
      if (len < 0) {
        return "";
      }
      if (static_cast<size_t>(len) == path.size()) {
        path.resize(path.size() * 2);
      } else {
        path.resize(static_cast<std::string::size_type>(len));
        break;
      }
    }

    return path;
  }