Get name of missing dependencies at runtime - The specified module could not be found

问题

The following code is part of a plugin system I'm developing. Basically it loads a DLL and, if fails, shows an error message.

HMODULE loadPlugin(LPTSTR path) {
    const auto module = LoadLibraryEx(path, NULL, LOAD_LIBRARY_SEARCH_DEFAULT_DIRS);

    if (module != nullptr) return module;

    LPTSTR errorText = nullptr;
    FormatMessage(FORMAT_MESSAGE_FROM_SYSTEM |
                  FORMAT_MESSAGE_ALLOCATE_BUFFER |
                  FORMAT_MESSAGE_IGNORE_INSERTS,
                  NULL, GetLastError(), 0,
                  (LPTSTR)&errorText, 0, NULL);

    if (errorText != nullptr) {
        MessageBox(0, errorText, L"Error", MB_OK | MB_ICONWARNING);
        LocalFree(errorText);
        errorText = NULL;
    }

    return nullptr;
}

The most common error is a missing dependency of the DLL being loaded (also applies for dependencies of dependencies, and so on): The specified module could not be found. Unfortunately, this error is not very helpful in order to know which dependency is.

I know I can use Dependency Walker to find it manually (actually it's how I'm doing it right now), but the process is quite complex since, as you noted by the LOAD_LIBRARY_SEARCH_DEFAULT_DIRS flag, dependencies can be located in different directories. The search path is specified before loading the plugin using AddDllDirectory, and restored with RemoveDllDirectory after it is loaded.

For reason above, using Dependency Walker is quite tedious: for each plugin that fails I have to add the directories used to load that plugin (there are many plugins and each one may have a different search path set).

Question: is there any way to know, at runtime, the name of the module that wasn't found? I'm the developer of the plugins too, so I can modify them if necessary.

Additional notes: Using Visual Studio 2017, and almost all the dependencies (DLLs) have exported symbols (.lib file associated and linked with the plugin).

来源：https://stackoverflow.com/questions/44430822/get-name-of-missing-dependencies-at-runtime-the-specified-module-could-not-be

标签

c++

winapi

dependencies

loadlibrary