diff --git a/4tech_defines.h b/4tech_defines.h
index 648c6ad6..3fe56aa9 100644
--- a/4tech_defines.h
+++ b/4tech_defines.h
@@ -42,6 +42,7 @@ typedef double f64;
 #define global static
 #define local_const static const
 #define global_const static const
+#define external extern "C"
 
 #define ArrayCount(a) ((sizeof(a))/(sizeof(*a)))
 #define ExpandArray(a) (a), (ArrayCount(a))
diff --git a/osx_objective_c_to_cpp_links.h b/osx_objective_c_to_cpp_links.h
index 20cdc62f..b374b59a 100644
--- a/osx_objective_c_to_cpp_links.h
+++ b/osx_objective_c_to_cpp_links.h
@@ -41,29 +41,29 @@ typedef struct OSX_Vars{
 // In C++ layer.
 extern OSX_Vars osx;
 
-void*
+external void*
 osx_allocate(umem size);
 
-void
+external void
 osx_resize(int width, int height);
 
-void
+external void
 osx_character_input(u32 code, OSX_Keyboard_Modifiers modifier_flags);
 
-void
+external void
 osx_mouse(i32 mx, i32 my, u32 type);
 
-void
+external void
 osx_mouse_wheel(float dx, float dy);
 
-void
+external void
 osx_step();
 
-void
+external void
 osx_init();
 
 // In Objective-C layer.
-void
+external void
 osx_post_to_clipboard(char *str);
 
 #endif
diff --git a/platform_mac/mac_4ed.cpp b/platform_mac/mac_4ed.cpp
index 945a6c75..9a3a5f3c 100644
--- a/platform_mac/mac_4ed.cpp
+++ b/platform_mac/mac_4ed.cpp
@@ -18,40 +18,40 @@ OSX_Vars osx;
 
 // TODO(allen): Implement a real allocate
 #include <stdlib.h>
-void*
+external void*
 osx_allocate(umem size){
     void *result = malloc(size);
     return(result);
 }
 
-void
+external void
 osx_resize(int width, int height){
     osx.width = width;
     osx.height = height;
     // TODO
 }
 
-void
+external void
 osx_character_input(u32 code, OSX_Keyboard_Modifiers modifier_flags){
     // TODO
 }
 
-void
+external void
 osx_mouse(i32 mx, i32 my, u32 type){
     // TODO
 }
 
-void
+external void
 osx_mouse_wheel(float dx, float dy){
     // TODO
 }
 
-void
+external void
 osx_step(){
     // TODO
 }
 
-void
+external void
 osx_init(){
     // TODO
 }