* src/pgtkmenu.c (menu_highlight_callback, menubar_selection_callback)
(popup_selection_callback):
* src/pgtkterm.c (size_allocate, pgtk_set_event_handler): Use
'gc_handle' or raw pointer, not 'glib_user_data'.

* src/pgtkfns.c:
* src/pgtkim.c:
* src/pgtkmenu.c:
* src/pgtkselect.c:
* src/pgtkterm.c:
* src/termcap.c:
* src/tparam.c: Delete superfluous comments explaining config.h.

* src/pgtkfns.c (Fx_create_frame):
(x_create_tip_frame): Use 'igc_xzalloc_ambig', not 'xzalloc'.
* src/pgtkmenu.c (pgtk_menu_show): Use 'SAFE_ALLOCA_LISP'.
* src/pgtkselect.c (pgtk_own_selection): Use temporary copies of the
symbol name strings.
(lisp_data_to_selection_data): Use temporary string copy.
* src/pgtkterm.c (pgtk_enumerate_devices):
(pgtk_free_devices):
(evq_enqueue): Use 'igc_xzalloc_ambig' etc.
(size_allocate): Use 'get_glib_user_data'.
(pgtk_link_touch_point):
(pgtk_unlink_touch_point):
(pgtk_unlink_touch_points):
(pgtk_free_frame_resources):
(pgtk_delete_display): Use 'igc_xzalloc_ambig' etc.
(pgtk_set_event_handler): Use 'glib_user_data'.

* src/gtkutil.c (style_changed_cb):
(xg_dialog_response_cb):
(xg_toggle_notify_cb):
(xg_finish_scroll_bar_creation):
(menu_bar_button_pressed_cb):
(find_scrollbar_cb):
(create_menus):
(xg_create_frame_widgets):
(xg_create_frame_outer_widgets):
(xg_tool_bar_callback):
(xg_tool_bar_help_callback):
(xg_make_tool_item):
(xg_dialog_run):
(xg_get_file_with_chooser):
(xg_get_widget_from_map): Use glib_user_data, free_glib_user_data.
* src/pgtkmenu.c (menubar_selection_callback):
(popup_selection_callback): Use glib_user_data, get_glib_user_data.

* src/pgtkmenu.c (pgtk_menu_show): Do not dereference save_wv if
null.  Problem found by gcc 20250110 (Red Hat 14.2.1-7)
-Wanalyzer-null-dereference.

* src/pgtkmenu.c (pgtk_menu_show): USE_SAFE_ALLOCA instead of alloca.
Problem found with --enable-gcc-warnings.

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