ci: fix warnings and enable --werror for the mingw build

Fix various warnings regarding unused variables, duplicated
branches etc by adjusting the ifdeffery and some missing casts.

gnulib triggers -Wduplicated-branches in one of the copied files,
disable as that just makes updating the code harder.

The warning indicating missing features are made none fatal through
pragmas. They still show but don't abort the build.

https://bugzilla.gnome.org/show_bug.cgi?id=793729

.gitlab-ci/test-msys2.sh

@@ -26,8 +26,7 @@ mkdir -p _ccache
 export CCACHE_BASEDIR="$(pwd)"
 export CCACHE_DIR="${CCACHE_BASEDIR}/_ccache"
 
-# FIXME: Add --werror
+meson --werror --buildtype debug _build
-meson --buildtype debug _build
 cd _build
 ninja
 

gio/gcredentials.c

@@ -95,7 +95,10 @@ struct _GCredentials
   ucred_t *native;
 #else
   #ifdef __GNUC__
+  #pragma GCC diagnostic push
+  #pragma GCC diagnostic warning "-Wcpp"
   #warning Please add GCredentials support for your OS
+  #pragma GCC diagnostic pop
   #endif
 #endif
 };

gio/gdbusauthmechanismexternal.c

@@ -348,7 +348,10 @@ mechanism_client_initiate (GDBusAuthMechanism   *mechanism,
  *out_initial_response_len = strlen (initial_response);
 #elif defined(G_OS_WIN32)
 #ifdef __GNUC__
+#pragma GCC diagnostic push
+#pragma GCC diagnostic warning "-Wcpp"
 #warning Dont know how to send credentials on this OS. The EXTERNAL D-Bus authentication mechanism will not work.
+#pragma GCC diagnostic pop
 #endif
   m->priv->state = G_DBUS_AUTH_MECHANISM_STATE_REJECTED;
 #endif

gio/gdbusauthmechanismsha1.c

@@ -280,7 +280,10 @@ ensure_keyring_directory (GError **error)
             }
 #else
 #ifdef __GNUC__
+#pragma GCC diagnostic push
+#pragma GCC diagnostic warning "-Wcpp"
 #warning Please implement permission checking on this non-UNIX platform
+#pragma GCC diagnostic pop
 #endif
 #endif
         }

gio/glocalfile.c

@@ -2819,7 +2819,9 @@ g_local_file_measure_size_of_file (gint           parent_fd,
   if (S_ISDIR (buf.st_mode))
     {
       int dir_fd = -1;
+#ifdef AT_FDCWD
       int errsv;
+#endif
 
       if (g_cancellable_set_error_if_cancelled (state->cancellable, error))
         return FALSE;

gio/glocalfileinfo.c

@@ -897,19 +897,21 @@ get_access_rights (GFileAttributeMatcher *attribute_matcher,
       writable = FALSE;
       if (parent_info->writable)
 	{
+#ifdef G_OS_WIN32
+	  writable = TRUE;
+#else
 	  if (parent_info->is_sticky)
 	    {
-#ifndef G_OS_WIN32
 	      uid_t uid = geteuid ();
 
 	      if (uid == statbuf->st_uid ||
 		  uid == parent_info->owner ||
 		  uid == 0)
-#endif
 		writable = TRUE;
 	    }
 	  else
 	    writable = TRUE;
+#endif
 	}
 
       if (_g_file_attribute_matcher_matches_id (attribute_matcher, G_FILE_ATTRIBUTE_ID_ACCESS_CAN_RENAME))

gio/glocalvfs.c

@@ -129,7 +129,7 @@ g_local_vfs_parse_name (GVfs       *vfs,
   GFile *file;
   char *filename;
   char *user_prefix;
-  const char *user_start, *user_end;
+  const char *user_end;
   char *rest;
   
   g_return_val_if_fail (G_IS_VFS (vfs), NULL);
@@ -141,19 +141,22 @@ g_local_vfs_parse_name (GVfs       *vfs,
     {
       if (*parse_name == '~')
 	{
+#ifdef G_OS_UNIX
+	  const char *user_start;
+	  user_start = parse_name + 1;
+#endif
 	  parse_name ++;
-	  user_start = parse_name;
 	  
 	  while (*parse_name != 0 && *parse_name != '/')
 	    parse_name++;
 	  
 	  user_end = parse_name;
 
+#ifdef G_OS_UNIX
 	  if (user_end == user_start)
 	    user_prefix = g_strdup (g_get_home_dir ());
 	  else
 	    {
-#ifdef G_OS_UNIX
               struct passwd *passwd_file_entry;
               char *user_name;
 
@@ -165,9 +168,11 @@ g_local_vfs_parse_name (GVfs       *vfs,
 		  passwd_file_entry->pw_dir != NULL)
 		user_prefix = g_strdup (passwd_file_entry->pw_dir);
 	      else
-#endif
 		user_prefix = g_strdup (g_get_home_dir ());
 	    }
+#else
+	  user_prefix = g_strdup (g_get_home_dir ());
+#endif
 
 	  rest = NULL;
 	  if (*user_end != 0)

gio/gregistrysettingsbackend.c

@@ -1800,7 +1800,7 @@ watch_thread_function (LPVOID parameter)
            * likely to block (only when changing notification subscriptions).
            */
           event = g_slice_new (RegistryEvent);
-          event->self = g_object_ref (self->owner);
+          event->self = G_REGISTRY_BACKEND (g_object_ref (self->owner));
           event->prefix = g_strdup (prefix);
           event->items = g_ptr_array_new_with_free_func (g_free);
 

gio/gsocket.c

@@ -572,7 +572,7 @@ g_socket (gint     domain,
 
   if (fd < 0)
     {
-      int errsv = get_socket_errno ();
+      errsv = get_socket_errno ();
 
       g_set_error (error, G_IO_ERROR, socket_io_error_from_errno (errsv),
 		   _("Unable to create socket: %s"), socket_strerror (errsv));
@@ -3251,7 +3251,7 @@ g_socket_send_with_timeout (GSocket       *socket,
     {
       win32_unset_event_mask (socket, FD_WRITE);
 
-      if ((ret = send (socket->priv->fd, buffer, size, G_SOCKET_DEFAULT_SEND_FLAGS)) < 0)
+      if ((ret = send (socket->priv->fd, (const char *)buffer, size, G_SOCKET_DEFAULT_SEND_FLAGS)) < 0)
 	{
 	  int errsv = get_socket_errno ();
 

glib/gmessages.c

@@ -1533,7 +1533,6 @@ static gboolean
 win32_is_pipe_tty (int fd)
 {
   gboolean result = FALSE;
-  int error;
   HANDLE h_fd;
   FILE_NAME_INFO *info = NULL;
   gint info_size = sizeof (FILE_NAME_INFO) + sizeof (WCHAR) * MAX_PATH;

glib/gnulib/meson.build

@@ -1,6 +1,7 @@
 # glib enables -Werror=format-nonliteral by default, but the embedded gnulib
 # needs to handle user provided format strings.
-extra_gnulib_args = cc.get_supported_arguments(['-Wno-format-nonliteral'])
+extra_gnulib_args = cc.get_supported_arguments([
+  '-Wno-format-nonliteral', '-Wno-duplicated-branches'])
 
 gnulib_lib = static_library('gnulib', 'asnprintf.c', 'printf.c', 'printf-args.c', 'printf-parse.c', 'vasnprintf.c',
   include_directories : [configinc, glibinc],

glib/gslice.c

@@ -1432,11 +1432,15 @@ allocator_memalign (gsize alignment,
           guint8 *amem = (guint8*) ALIGN ((gsize) mem, sys_page_size);
           if (amem != mem)
             i--;        /* mem wasn't page aligned */
+          G_GNUC_BEGIN_IGNORE_DEPRECATIONS
           while (--i >= 0)
             g_trash_stack_push (&compat_valloc_trash, amem + i * sys_page_size);
+          G_GNUC_END_IGNORE_DEPRECATIONS
         }
     }
+  G_GNUC_BEGIN_IGNORE_DEPRECATIONS
   aligned_memory = g_trash_stack_pop (&compat_valloc_trash);
+  G_GNUC_END_IGNORE_DEPRECATIONS
 #endif
   if (!aligned_memory)
     errno = err;
@@ -1451,7 +1455,9 @@ allocator_memfree (gsize    memsize,
   free (mem);
 #else
   mem_assert (memsize <= sys_page_size);
+  G_GNUC_BEGIN_IGNORE_DEPRECATIONS
   g_trash_stack_push (&compat_valloc_trash, mem);
+  G_GNUC_END_IGNORE_DEPRECATIONS
 #endif
 }
 

glib/gspawn-win32.c

@@ -544,7 +544,6 @@ do_spawn_with_pipes (gint                 *exit_status,
   GError *conv_error = NULL;
   gint conv_error_index;
   gchar *helper_process;
-  CONSOLE_CURSOR_INFO cursor_info;
   wchar_t *whelper, **wargv, **wenvp;
   gchar *glib_dll_directory;
 

glib/tests/mainloop.c

@@ -1150,6 +1150,7 @@ read_bytes (gint         fd,
   return TRUE;
 }
 
+#ifdef G_OS_UNIX
 static void
 test_unix_fd (void)
 {
@@ -1206,6 +1207,7 @@ test_unix_fd (void)
   close (fds[1]);
   close (fds[0]);
 }
+#endif
 
 static void
 assert_main_context_state (gint n_to_poll,
@@ -1513,6 +1515,7 @@ test_unix_file_poll (void)
 
 #endif
 
+#ifdef G_OS_UNIX
 static gboolean
 timeout_cb (gpointer data)
 {
@@ -1564,6 +1567,7 @@ test_mainloop_wait (void)
 
   g_main_context_unref (context);
 }
+#endif
 
 static gboolean
 nfds_in_cb (GIOChannel   *io,