# V1078. An empty container is iterated. The loop will not be executed.

The analyzer has detected an attempt to iterate an empty container. As a result, not a single iteration of the loop will occur. This may indicate an error.

Let's look at the example that may be the result of unsuccessful refactoring:

    #include <vector>
    #include <string_view>

    std::vector<std::string_view> GetSystemPaths()
    {
      std::vector<std::string_view> paths;

    #ifdef _WIN32
      paths.emplace_back("C:/Program files (x86)/Windows Kits");
      paths.emplace_back("C:/Program Files (x86)/Microsoft Visual Studio");
    #elif defined(__APPLE__)
      paths.emplace_back("/Applications");
      paths.emplace_back("/Library");
      paths.emplace_back("/usr/local/Cellar");
    #elif defined(__linux__)
      // TODO: Don't forget to add some specific paths
    #endif

      return paths;
    }

    bool IsSystemPath(std::string_view path)
    {
      static const auto system_paths = GetSystemPaths();

      for (std::string_view system_path : system_paths)
      {
        if (system_path == path)
        {
          return true;
        }
      }

      return false;
    }

The content of the 'system_paths' container depends on the operating system for which the application is compiled. For Linux and all other systems except Windows and macOS, an empty container is obtained as a result of the preprocessor directives expansion.

In the context of this example, this is an undesirable behavior of the 'GetSystemPaths' function. In the case of Linux, to fix the warning, a developer needs to add the necessary paths. When compiling to a new operating system (for example, FreeBSD) a developer may need to handle an error with static_assert. Here is the example of safe code:

    #include <vector>
    #include <string_view>

    std::vector<std::string_view> GetSystemPaths()
    {
      std::vector<std::string_view> paths;

    #ifdef _WIN32
      ....
    #elif defined(__APPLE__)
      ....
    #elif defined(__linux__)
      paths.emplace_back("/usr/include/");
      paths.emplace_back("/usr/local/include");
    #else
      static_assert(false, "Unsupported OS.");
    #endif

      return paths;
    }

In general, if an empty container iteration was the programmer's intent, then the warning can be suppressed.