Initialize DLL on nif load (#126)

Author: josevalim

c_src/dll_loader/adbc_dll_loader.cpp

@@ -9,39 +9,38 @@
 #include <winbase.h>
 #include <wchar.h>
 
-#define NIF(NAME) ERL_NIF_TERM NAME(ErlNifEnv *env, int argc, const ERL_NIF_TERM argv[])
-
-// Helper for returning `{:error, msg}` from NIF.
-ERL_NIF_TERM error(ErlNifEnv *env, const char *msg)
-{
-  ERL_NIF_TERM atom = enif_make_atom(env, "error");
-  ERL_NIF_TERM msg_term = enif_make_string(env, msg, ERL_NIF_LATIN1);
-  return enif_make_tuple2(env, atom, msg_term);
+ERL_NIF_TERM adbc_dll_unused(ErlNifEnv *env, int argc, const ERL_NIF_TERM argv[]) {
+  (void)(env);
+  (void)(argc);
+  (void)(argv);
+  return enif_make_int(env, 0);
 }
 
-// Helper for returning `{:ok, term}` from NIF.
-ERL_NIF_TERM ok(ErlNifEnv *env)
-{
-  return enif_make_atom(env, "ok");
-}
+int upgrade(ErlNifEnv *env, void **priv_data, void **old_priv_data, ERL_NIF_TERM load_info) {
+  // Silence "unused var" warnings.
+  (void)(env);
+  (void)(priv_data);
+  (void)(old_priv_data);
+  (void)(load_info);
 
-NIF(add_dll_directory) {
-  static bool path_updated = false;
-  if (path_updated) return ok(env);
+  return 0;
+}
 
+int load(ErlNifEnv *,void **,ERL_NIF_TERM) {
   wchar_t dll_path_c[65536];
   char err_msg[128] = { '\0' };
   HMODULE hm = NULL;
-  if (GetModuleHandleExW(GET_MODULE_HANDLE_EX_FLAG_FROM_ADDRESS | GET_MODULE_HANDLE_EX_FLAG_UNCHANGED_REFCOUNT, (LPCWSTR)&add_dll_directory, &hm) == 0) {
-    int ret = GetLastError();
-    snprintf(err_msg, sizeof(err_msg) - 1, "GetModuleHandle failed, error = %d\r\n", ret);
-    return error(env, err_msg);
+
+  if (GetModuleHandleExW(GET_MODULE_HANDLE_EX_FLAG_FROM_ADDRESS | GET_MODULE_HANDLE_EX_FLAG_UNCHANGED_REFCOUNT, (LPCWSTR)&load, &hm) == 0) {
+      int ret = GetLastError();
+      printf("GetModuleHandle failed, error = %d\n", ret);
+      return 1;
   }
 
   if (GetModuleFileNameW(hm, (LPWSTR)dll_path_c, sizeof(dll_path_c)) == 0) {
-    int ret = GetLastError();
-    snprintf(err_msg, sizeof(err_msg) - 1, "GetModuleFileName failed, error = %d\r\n", ret);
-    return error(env, err_msg);
+      int ret = GetLastError();
+      printf("GetModuleFileName failed, error = %d\n", ret);
+      return 1;
   }
 
   std::wstring dll_path = dll_path_c;
@@ -64,44 +63,27 @@ NIF(add_dll_directory) {
 
   SetDefaultDllDirectories(LOAD_LIBRARY_SEARCH_DEFAULT_DIRS | LOAD_LIBRARY_SEARCH_USER_DIRS);
   DLL_DIRECTORY_COOKIE ret = AddDllDirectory(directory_pcwstr);
+
   if (ret == 0) {
     DWORD last_error = GetLastError();
     LPTSTR error_text = nullptr;
     FormatMessage(FORMAT_MESSAGE_FROM_SYSTEM | FORMAT_MESSAGE_ALLOCATE_BUFFER | FORMAT_MESSAGE_IGNORE_INSERTS, NULL, HRESULT_FROM_WIN32(last_error), MAKELANGID(LANG_NEUTRAL, SUBLANG_DEFAULT), (LPTSTR)&error_text, 0, NULL);
+
     if (error_text != nullptr) {
-      ERL_NIF_TERM ret_term = error(env, error_text);
-      LocalFree(error_text);
-      return ret_term;
+        printf("Error: %s\n", error_text);
+        LocalFree(error_text);
     } else {
-      ERL_NIF_TERM ret_term = error(env, "error happened when adding adbc driver runtime path, but cannot get formatted error message");
-      return ret_term;
+        printf("Error: error happened when adding adbc driver runtime path, but cannot get formatted error message\n");
     }
-  }
-  path_updated = true;
-  return ok(env);
-}
-
-int upgrade(ErlNifEnv *env, void **priv_data, void **old_priv_data, ERL_NIF_TERM load_info) {
-  // Silence "unused var" warnings.
-  (void)(env);
-  (void)(priv_data);
-  (void)(old_priv_data);
-  (void)(load_info);
 
-  return 0;
-}
+    return 1;
+  }
 
-int load(ErlNifEnv *,void **,ERL_NIF_TERM) {
   return 0;
 }
 
-#define F(NAME, ARITY)    \
-  {                       \
-#NAME, ARITY, NAME, 0 \
-  }
-
 static ErlNifFunc nif_functions[] = {
-  F(add_dll_directory, 0)
+  {"__unused__", 0, adbc_dll_unused, 0}
 };
 
 ERL_NIF_INIT(Elixir.Adbc.DLLLoaderNif, nif_functions, load, NULL, upgrade, NULL);

lib/adbc_dll_loader_nif.ex

@@ -11,17 +11,13 @@ defmodule Adbc.DLLLoaderNif do
         File.mkdir_p!(Path.join(priv_dir, "bin"))
         path = :filename.join(priv_dir, ~c"adbc_dll_loader")
         :erlang.load_nif(path, 0)
-        add_dll_directory()
 
       _ ->
         :ok
     end
   end
 
-  def add_dll_directory do
-    case :os.type() do
-      {:win32, _} -> :erlang.nif_error(:not_loaded)
-      _ -> :ok
-    end
+  def __unused__ do
+    0
   end
 end