diff --git a/README.md b/README.md
index f5cf9634fe..55e4320cff 100644
--- a/README.md
+++ b/README.md
@@ -7,7 +7,7 @@ Vim - the text editor - for macOS
 
 - Vim README: [README_vim.md](README_vim.md)
 
-- [![MacVim GitHub CI](https://github.com/macvim-dev/macvim/workflows/MacVim%20GitHub%20CI/badge.svg)](https://github.com/macvim-dev/macvim/actions?query=workflow%3A%22MacVim+GitHub+CI%22)
+- [![MacVim GitHub CI](https://github.com/macvim-dev/macvim/actions/workflows/ci-macvim.yaml/badge.svg)](https://github.com/macvim-dev/macvim/actions/workflows/ci-macvim.yaml)
 
 - Packaged in [![Homebrew package](https://repology.org/badge/version-for-repo/homebrew/macvim.svg)](https://repology.org/metapackage/macvim/versions) [![MacPorts package](https://repology.org/badge/version-for-repo/macports/macvim.svg)](https://repology.org/metapackage/macvim/versions)
 
diff --git a/src/MacVim/MMBackend.m b/src/MacVim/MMBackend.m
index cce7d8ca83..5e3bc0ff45 100644
--- a/src/MacVim/MMBackend.m
+++ b/src/MacVim/MMBackend.m
@@ -28,6 +28,7 @@
  */
 
 #import "MMBackend.h"
+#include "gui_macvim.pro"
 
 
 
@@ -56,11 +57,6 @@
 
 static id evalExprCocoa(NSString * expr, NSString ** errstr);
 
-void im_preedit_start_macvim();
-void im_preedit_end_macvim();
-void im_preedit_abandon_macvim();
-void im_preedit_changed_macvim(char *preedit_string, int cursor_index);
-
 enum {
     MMBlinkStateNone = 0,
     MMBlinkStateOn,
@@ -149,9 +145,6 @@
 };
 
 
-extern GuiFont gui_mch_retain_font(GuiFont font);
-
-
 @interface NSString (MMServerNameCompare)
 - (NSComparisonResult)serverNameCompare:(NSString *)string;
 @end
@@ -1375,7 +1368,7 @@ - (NSString *)evaluateExpression:(in bycopy NSString *)expr
 /// Extracts the text currently selected in visual mode, and returns it.
 ///
 /// @return the string representing the selected text, or NULL if failure.
-static char_u *extractSelectedText()
+static char_u *extractSelectedText(void)
 {
     // Note: Most of the functionality in Vim that allows for extracting useful
     // text from a selection are in the register & clipboard utility functions.
diff --git a/src/MacVim/MacVim.h b/src/MacVim/MacVim.h
index 1f4328b6a7..6da8a3b757 100644
--- a/src/MacVim/MacVim.h
+++ b/src/MacVim/MacVim.h
@@ -505,7 +505,7 @@ extern NSString *VimFindPboardType;
 
 extern int ASLogLevel;
 
-void ASLInit();
+void ASLInit(void);
 
 #if defined(MM_USE_ASL)
 
diff --git a/src/MacVim/MacVim.m b/src/MacVim/MacVim.m
index c005048d5a..97d8d7e3b1 100644
--- a/src/MacVim/MacVim.m
+++ b/src/MacVim/MacVim.m
@@ -253,7 +253,7 @@ + (id)dictionaryWithData:(NSData *)data
 
 
     void
-ASLInit()
+ASLInit(void)
 {
     NSUserDefaults *ud = [NSUserDefaults standardUserDefaults];
 
diff --git a/src/MacVim/gui_macvim.m b/src/MacVim/gui_macvim.m
index 797926c58e..b0cc5b0cd6 100644
--- a/src/MacVim/gui_macvim.m
+++ b/src/MacVim/gui_macvim.m
@@ -49,7 +49,7 @@
 // -- Initialization --------------------------------------------------------
 
     void
-macvim_early_init()
+macvim_early_init(void)
 {
     NSBundle *bundle = [NSBundle mainBundle];
     if (bundle) {
@@ -145,7 +145,7 @@
 
 /* Called directly after forking (even if we didn't fork). */
     void
-gui_macvim_after_fork_init()
+gui_macvim_after_fork_init(void)
 {
     ASLInit();
     ASLogDebug(@"");
@@ -606,7 +606,7 @@
  * Set default colors.
  */
     void
-gui_mch_def_colors()
+gui_mch_def_colors(void)
 {
     MMBackend *backend = [MMBackend sharedInstance];
 
@@ -1385,8 +1385,6 @@
 // -- Input Method ----------------------------------------------------------
 
 #if defined(FEAT_EVAL)
-void call_imactivatefunc(int active);
-int call_imstatusfunc(void);
 # ifdef FEAT_GUI
 #  define USE_IMACTIVATEFUNC (!gui.in_use && *p_imaf != NUL)
 #  define USE_IMSTATUSFUNC (!gui.in_use && *p_imsf != NUL)
@@ -1819,7 +1817,7 @@
  * adding / removing a toolbar) when guioptions 'k' is set.
  */
     void
-gui_mch_resize_view()
+gui_mch_resize_view(void)
 {
     [[MMBackend sharedInstance] resizeView];
 }
@@ -1892,14 +1890,14 @@
 
 
     void
-gui_mch_leave_fullscreen()
+gui_mch_leave_fullscreen(void)
 {
     [[MMBackend sharedInstance] leaveFullScreen];
 }
 
 
     void
-gui_mch_fuopt_update()
+gui_mch_fuopt_update(void)
 {
     if (!gui.in_use)
         return;
@@ -1916,7 +1914,7 @@
 
 
     void
-gui_macvim_update_modified_flag()
+gui_macvim_update_modified_flag(void)
 {
     [[MMBackend sharedInstance] updateModifiedFlag];
 }
@@ -1983,7 +1981,7 @@
 }
 
     void
-gui_macvim_wait_for_startup()
+gui_macvim_wait_for_startup(void)
 {
     MMBackend *backend = [MMBackend sharedInstance];
     if ([backend waitForAck])
@@ -2006,7 +2004,7 @@
 }
 
     void *
-gui_macvim_new_autoreleasepool()
+gui_macvim_new_autoreleasepool(void)
 {
     return (void *)[[NSAutoreleasePool alloc] init];
 }
diff --git a/src/ex_cmds2.c b/src/ex_cmds2.c
index 435bea474c..6372446b70 100644
--- a/src/ex_cmds2.c
+++ b/src/ex_cmds2.c
@@ -155,7 +155,7 @@ browse_save_fname(buf_T *buf)
 /*
  * "Save changes" dialog that conforms to the Apple HIG.
  */
-    int
+    static int
 vim_dialog_save_changes(buf_T *buf)
 {
     char_u	buff[IOSIZE];
@@ -181,7 +181,7 @@ vim_dialog_save_changes(buf_T *buf)
  * "Save all changes" dialog that tries to emulate the above "Save changes"
  * dialog for the case of several modified buffers.
  */
-    int
+    static int
 vim_dialog_save_all_changes(buf_T *buf)
 {
     char_u	buff[IOSIZE];
diff --git a/src/gui_xim.c b/src/gui_xim.c
index 4d789c544f..3a7abaef98 100644
--- a/src/gui_xim.c
+++ b/src/gui_xim.c
@@ -634,7 +634,7 @@ im_commit_cb(GtkIMContext *context UNUSED,
 im_preedit_start_cb(GtkIMContext *context UNUSED, gpointer data UNUSED)
 # else
     void
-im_preedit_start_macvim()
+im_preedit_start_macvim(void)
 # endif
 {
 #ifdef XIM_DEBUG
@@ -655,7 +655,7 @@ im_preedit_start_macvim()
 im_preedit_end_cb(GtkIMContext *context UNUSED, gpointer data UNUSED)
 # else
     void
-im_preedit_end_macvim()
+im_preedit_end_macvim(void)
 # endif
 {
 #ifdef XIM_DEBUG
@@ -681,7 +681,7 @@ im_preedit_end_macvim()
 
 #ifdef FEAT_GUI_MACVIM
     void
-im_preedit_abandon_macvim()
+im_preedit_abandon_macvim(void)
 {
     /* Abandon preedit text, don't send any backspace sequences. */
     im_preedit_cursor = 0;
diff --git a/src/os_macosx.m b/src/os_macosx.m
index 9b7128ba22..c49678150c 100644
--- a/src/os_macosx.m
+++ b/src/os_macosx.m
@@ -524,7 +524,7 @@ - (void) sound:(NSSound *)sound didFinishPlaying:(BOOL)flag
 #endif
 
     void
-macosx_fork()
+macosx_fork(void)
 {
     pid_t pid;
     int   i;
diff --git a/src/proto.h b/src/proto.h
index 2ff290944e..b5f217d746 100644
--- a/src/proto.h
+++ b/src/proto.h
@@ -344,7 +344,4 @@ int clip_mch_own_selection(Clipboard_T *cbd);
 void clip_mch_request_selection(Clipboard_T *cbd);
 void clip_mch_set_selection(Clipboard_T *cbd);
 # endif
-# if defined(MACOS_X) && defined(FEAT_GUI)
-void macosx_fork();
-# endif
 #endif // !PROTO && !NOPROTO
diff --git a/src/proto/gui_macvim.pro b/src/proto/gui_macvim.pro
index d60abae7d2..8e47a4db32 100644
--- a/src/proto/gui_macvim.pro
+++ b/src/proto/gui_macvim.pro
@@ -1,6 +1,6 @@
-void macvim_early_init();
+void macvim_early_init(void);
 void gui_mch_prepare(int *argc, char **argv);
-void gui_macvim_after_fork_init();
+void gui_macvim_after_fork_init(void);
 int gui_mch_init_check(void);
 int gui_mch_init(void);
 void gui_mch_exit(int rc);
@@ -35,6 +35,7 @@ void gui_mch_draw_menubar(void);
 void gui_mch_enable_menu(int flag);
 void gui_mch_show_toolbar(int showit);
 void gui_mch_free_font(GuiFont font);
+GuiFont gui_mch_retain_font(GuiFont font);
 GuiFont gui_mch_get_font(char_u *name, int giveErrorIfMissing);
 char_u *gui_mch_get_fontname(GuiFont font, char_u *name);
 int gui_mch_init_font(char_u *font_name, int fontset);
@@ -72,7 +73,7 @@ int gui_mch_get_scrollbar_xpadding(void);
 int gui_mch_get_scrollbar_ypadding(void);
 void gui_mch_set_scrollbar_thumb(scrollbar_T *sb, long val, long size, long max);
 void gui_mch_set_shellsize(int width, int height, int min_width, int min_height, int base_width, int base_height, int direction);
-void gui_mch_resize_view();
+void gui_mch_resize_view(void);
 void gui_mch_set_sp_color(guicolor_T color);
 void gui_mch_set_text_area_pos(int x, int y, int w, int h);
 void gui_mch_set_winpos(int x, int y);
@@ -83,7 +84,7 @@ void gui_mch_start_blink(void);
 void gui_mch_stop_blink(int may_call_gui_update_cursor);
 void gui_mch_toggle_tearoffs(int enable);
 void mch_set_mouse_shape(int shape);
-void gui_mch_def_colors();
+void gui_mch_def_colors(void);
 void ex_macaction(exarg_T *eap);
 void gui_make_popup(char_u *path_name, int mouse_pos);
 
@@ -99,7 +100,7 @@ void gui_mch_enter_fullscreen(guicolor_T bg);
 void gui_mch_leave_fullscreen(void);
 void gui_mch_fuopt_update(void);
 
-void gui_macvim_update_modified_flag();
+void gui_macvim_update_modified_flag(void);
 void gui_macvim_add_to_find_pboard(char_u *pat);
 void gui_macvim_set_antialias(int antialias);
 void gui_macvim_set_ligatures(int ligatures);
@@ -115,7 +116,7 @@ void odb_end(void);
 char_u *get_macaction_name(expand_T *xp, int idx);
 int is_valid_macaction(char_u *action);
 
-void gui_macvim_wait_for_startup();
+void gui_macvim_wait_for_startup(void);
 void gui_macvim_get_window_layout(int *count, int *layout);
 
 void gui_mch_find_dialog(exarg_T *eap);
@@ -132,7 +133,7 @@ void *gui_mch_register_sign(char_u *signfile);
 
 void gui_mch_destroy_sign(void *sign);
 
-void *gui_macvim_new_autoreleasepool();
+void *gui_macvim_new_autoreleasepool(void);
 void gui_macvim_release_autoreleasepool(void *pool);
 
 void f_showdefinition(typval_T *argvars, typval_T *rettv);
diff --git a/src/proto/gui_xim.pro b/src/proto/gui_xim.pro
index bac7321de9..0768db7a2c 100644
--- a/src/proto/gui_xim.pro
+++ b/src/proto/gui_xim.pro
@@ -18,4 +18,12 @@ int preedit_get_status(void);
 int im_is_preediting(void);
 void xim_set_status_area(void);
 int xim_get_status_area_height(void);
+
+// MacVim
+void call_imactivatefunc(int active);
+int call_imstatusfunc(void);
+void im_preedit_start_macvim(void);
+void im_preedit_end_macvim(void);
+void im_preedit_abandon_macvim(void);
+void im_preedit_changed_macvim(char *preedit_string, int cursor_index);
 /* vim: set ft=c : */
diff --git a/src/proto/os_macosx.pro b/src/proto/os_macosx.pro
index c7f94ec9e2..96a3c4c271 100644
--- a/src/proto/os_macosx.pro
+++ b/src/proto/os_macosx.pro
@@ -4,4 +4,7 @@ bool sound_mch_play(const char_u* event, long sound_id, soundcb_T *callback, boo
 void sound_mch_stop(long sound_id);
 void sound_mch_clear(void);
 void sound_mch_free(void);
+
+// MacVim
+void macosx_fork(void);
 /* vim: set ft=c : */