diff --git a/common/arch/sdl/digi_mixer_music.cpp b/common/arch/sdl/digi_mixer_music.cpp
index d22fdcce6..ba640d061 100644
--- a/common/arch/sdl/digi_mixer_music.cpp
+++ b/common/arch/sdl/digi_mixer_music.cpp
@@ -25,6 +25,8 @@
 #include "u_mem.h"
 #include "console.h"
 
+inline namespace dcx {
+
 namespace {
 
 class current_music_t
@@ -184,3 +186,5 @@ void mix_pause_resume_music()
 	else if (Mix_PlayingMusic())
 		Mix_PauseMusic();
 }
+
+}
diff --git a/common/arch/sdl/event.cpp b/common/arch/sdl/event.cpp
index 52bda327b..941de03dd 100644
--- a/common/arch/sdl/event.cpp
+++ b/common/arch/sdl/event.cpp
@@ -25,6 +25,8 @@
 #include "joy.h"
 #include "args.h"
 
+inline namespace dcx {
+
 void event_poll()
 {
 	SDL_Event event;
@@ -200,3 +202,4 @@ fix event_get_idle_seconds()
 	return (timer_query() - last_event)/F1_0;
 }
 
+}
diff --git a/common/arch/sdl/joy.cpp b/common/arch/sdl/joy.cpp
index 98888345b..fd68eee62 100644
--- a/common/arch/sdl/joy.cpp
+++ b/common/arch/sdl/joy.cpp
@@ -26,6 +26,8 @@
 #include "compiler-integer_sequence.h"
 #include "compiler-type_traits.h"
 
+inline namespace dcx {
+
 namespace {
 
 int num_joysticks = 0;
@@ -381,4 +383,6 @@ int event_joystick_get_button(const d_event &event)
 	Assert(e.type == EVENT_JOYSTICK_BUTTON_DOWN || e.type == EVENT_JOYSTICK_BUTTON_UP);
 	return e.button;
 }
+
+}
 #endif
diff --git a/common/arch/sdl/key.cpp b/common/arch/sdl/key.cpp
index 35a06e86d..8ff3f315b 100644
--- a/common/arch/sdl/key.cpp
+++ b/common/arch/sdl/key.cpp
@@ -28,6 +28,8 @@
 #include "dxxsconf.h"
 #include "compiler-array.h"
 
+inline namespace dcx {
+
 //-------- Variable accessed by outside functions ---------
 static bool keyd_repeat; // 1 = use repeats, 0 no repeats
 pressed_keys keyd_pressed;
@@ -509,3 +511,5 @@ void key_toggle_repeat(int enable)
 	}
 	key_flush();
 }
+
+}
diff --git a/common/arch/sdl/mouse.cpp b/common/arch/sdl/mouse.cpp
index 75b6e3854..fb5e9041f 100644
--- a/common/arch/sdl/mouse.cpp
+++ b/common/arch/sdl/mouse.cpp
@@ -23,6 +23,8 @@
 #include "args.h"
 #include "gr.h"
 
+inline namespace dcx {
+
 namespace {
 
 struct flushable_mouseinfo
@@ -251,3 +253,5 @@ void mouse_cursor_autohide()
 	}
 	SDL_ShowCursor(result);
 }
+
+}
diff --git a/common/arch/sdl/rbaudio.cpp b/common/arch/sdl/rbaudio.cpp
index 2be01dc6d..908b29903 100644
--- a/common/arch/sdl/rbaudio.cpp
+++ b/common/arch/sdl/rbaudio.cpp
@@ -31,6 +31,8 @@
 #include "partial_range.h"
 #include "compiler-range_for.h"
 
+inline namespace dcx {
+
 #define REDBOOK_VOLUME_SCALE 255
 
 static SDL_CD *s_cd = NULL;
@@ -319,3 +321,5 @@ void RBAList(void)
 	range_for (auto &i, partial_range(s_cd->track, static_cast<unsigned>(s_cd->numtracks)))
 		con_printf(CON_VERBOSE, "RBAudio: CD track %d, type %s, length %d, offset %d", i.id, (i.type == SDL_AUDIO_TRACK) ? "audio" : "data", i.length, i.offset);
 }
+
+}
diff --git a/common/arch/sdl/timer.cpp b/common/arch/sdl/timer.cpp
index 0dd7a4ff9..c08489c60 100644
--- a/common/arch/sdl/timer.cpp
+++ b/common/arch/sdl/timer.cpp
@@ -17,6 +17,8 @@
 #include "config.h"
 #include "multi.h"
 
+inline namespace dcx {
+
 static fix64 F64_RunTime = 0;
 
 fix64 timer_update()
@@ -71,3 +73,5 @@ void timer_delay_bound(const unsigned caller_bound)
 		}
 	}
 }
+
+}
diff --git a/common/arch/sdl/window.cpp b/common/arch/sdl/window.cpp
index ffed5e5cb..a680ad41e 100644
--- a/common/arch/sdl/window.cpp
+++ b/common/arch/sdl/window.cpp
@@ -20,6 +20,8 @@
 #include "dxxerror.h"
 #include "event.h"
 
+inline namespace dcx {
+
 struct window
 {
 	grs_canvas w_canv;					// the window's canvas to draw to
@@ -221,3 +223,5 @@ int window_is_modal(window &wind)
 {
 	return wind.w_modal;
 }
+
+}
diff --git a/common/include/digi_mixer_music.h b/common/include/digi_mixer_music.h
index 7cbf9200a..acb286c8b 100644
--- a/common/include/digi_mixer_music.h
+++ b/common/include/digi_mixer_music.h
@@ -10,10 +10,10 @@
  *  -- MD2211 (2006-04-24)
  */
 
-#ifndef _SDLMIXER_MUSIC_H
-#define _SDLMIXER_MUSIC_H
+#pragma once
 
 #ifdef __cplusplus
+inline namespace dcx {
 
 int mix_play_music(const char *, int);
 int mix_play_file(const char *, int, void (*)());
@@ -24,6 +24,5 @@ void mix_resume_music();
 void mix_pause_resume_music();
 void mix_free_music();
 
-#endif
-
+}
 #endif
diff --git a/common/include/editor/editor.h b/common/include/editor/editor.h
index 9129de9ff..cf714c147 100644
--- a/common/include/editor/editor.h
+++ b/common/include/editor/editor.h
@@ -30,10 +30,8 @@ COPYRIGHT 1993-1999 PARALLAX SOFTWARE CORPORATION.  ALL RIGHTS RESERVED.
 #include "ui.h"
 #include "fmtcheck.h"
 
-struct window;
-
 #ifdef __cplusplus
-
+#include "fwd-window.h"
 #include "fwd-segment.h"
 #include "objnum.h"
 
diff --git a/common/include/editor/info.h b/common/include/editor/info.h
index d69c482e3..7dfba4341 100644
--- a/common/include/editor/info.h
+++ b/common/include/editor/info.h
@@ -23,17 +23,13 @@ COPYRIGHT 1993-1998 PARALLAX SOFTWARE CORPORATION.  ALL RIGHTS RESERVED.
  *
  */
 
-#ifndef _INFO_H
-#define _INFO_H
+#pragma once
 
 #ifdef __cplusplus
-
-struct window;
+#include "fwd-window.h"
 
 struct window *info_window_create(void);
 
 extern int init_info;
 
 #endif
-
-#endif
diff --git a/common/include/editor/objpage.h b/common/include/editor/objpage.h
index 7f67643d9..c42ee5f56 100644
--- a/common/include/editor/objpage.h
+++ b/common/include/editor/objpage.h
@@ -23,14 +23,13 @@ COPYRIGHT 1993-1998 PARALLAX SOFTWARE CORPORATION.  ALL RIGHTS RESERVED.
  *
  */
 
-#ifndef _OBJPAGE_H
-#define _OBJPAGE_H
+#pragma once
 
 #include "ui.h"
 
 #ifdef __cplusplus
+#include "fwd-event.h"
 
-struct d_event;
 struct vms_angvec;
 
 int objpage_grab_current(int n);
@@ -43,5 +42,3 @@ int objpage_do(const d_event &event);
 extern void draw_object_picture(int id, vms_angvec *orient_angles, int type);
 
 #endif
-
-#endif
diff --git a/common/include/editor/texpage.h b/common/include/editor/texpage.h
index a1b9b492f..f88f2aba8 100644
--- a/common/include/editor/texpage.h
+++ b/common/include/editor/texpage.h
@@ -29,8 +29,7 @@ COPYRIGHT 1993-1999 PARALLAX SOFTWARE CORPORATION.  ALL RIGHTS RESERVED.
 #include "ui.h"
 
 #ifdef __cplusplus
-
-struct d_event;
+#include "fwd-event.h"
 
 extern int TextureLights;
 extern int TextureEffects;
diff --git a/common/include/event.h b/common/include/event.h
index 75052db2a..e981b27af 100644
--- a/common/include/event.h
+++ b/common/include/event.h
@@ -12,6 +12,7 @@
 #include "maths.h"
 
 #ifdef __cplusplus
+inline namespace dcx {
 
 enum event_type : unsigned
 {
@@ -79,4 +80,5 @@ struct d_select_event : d_event
 
 fix event_get_idle_seconds();
 
+}
 #endif
diff --git a/common/include/fwd-event.h b/common/include/fwd-event.h
index 6e107b3c9..57af9762a 100644
--- a/common/include/fwd-event.h
+++ b/common/include/fwd-event.h
@@ -7,13 +7,13 @@
 
 #pragma once
 
+inline namespace dcx {
+
 struct d_event;
 struct d_create_event;
 struct d_change_event;
 struct d_select_event;
 
-#ifdef __cplusplus
-
 enum event_type : unsigned;
 
 int event_init();
@@ -44,4 +44,4 @@ static inline void event_toggle_focus(int activate_focus)
 // See how long we were idle for
 void event_reset_idle_seconds();
 
-#endif
+}
diff --git a/common/include/fwd-window.h b/common/include/fwd-window.h
index 9eb0f0dad..71b30be0f 100644
--- a/common/include/fwd-window.h
+++ b/common/include/fwd-window.h
@@ -11,9 +11,11 @@
 #include "fwd-event.h"
 #include "fwd-gr.h"
 
+void arch_init();
+inline namespace dcx {
+
 struct window;
 enum class window_event_result : uint8_t;
-void arch_init();
 
 template <typename T>
 using window_subfunction = window_event_result (*)(window *menu,const d_event &event, T *userdata);
@@ -45,4 +47,6 @@ int window_is_modal(window &wind);
 
 #define WINDOW_SEND_EVENT(w, e)	(event.type = e, (WINDOW_SEND_EVENT)(*w, event, __FILE__, __LINE__, #e))
 
+}
+
 #endif
diff --git a/common/include/joy.h b/common/include/joy.h
index c115d3661..81debbc4b 100644
--- a/common/include/joy.h
+++ b/common/include/joy.h
@@ -19,7 +19,7 @@
 #include "maths.h"
 #include <SDL.h>
 
-#ifdef __cplusplus
+inline namespace dcx {
 
 struct d_event;
 
@@ -37,13 +37,16 @@ extern void joy_close();
 const d_event_joystick_axis_value &event_joystick_get_axis(const d_event &event);
 extern void joy_flush();
 extern int event_joystick_get_button(const d_event &event);
-#endif
+
+}
 #else
 #define joy_init()
 #define joy_flush()
 #define joy_close()
 #endif
 
+inline namespace dcx {
+
 #if MAX_BUTTONS_PER_JOYSTICK
 extern void joy_button_handler(SDL_JoyButtonEvent *jbe);
 #else
@@ -61,3 +64,5 @@ extern int joy_axis_handler(SDL_JoyAxisEvent *jae);
 #else
 #define joy_axis_handler(jae)	(static_cast<void>(static_cast<SDL_JoyAxisEvent *const &>(jae)), 1)
 #endif
+
+}
diff --git a/common/include/key.h b/common/include/key.h
index d27cb385a..7e56006d2 100644
--- a/common/include/key.h
+++ b/common/include/key.h
@@ -41,6 +41,8 @@ COPYRIGHT 1993-1999 PARALLAX SOFTWARE CORPORATION.  ALL RIGHTS RESERVED.
 
 struct SDL_KeyboardEvent;
 
+inline namespace dcx {
+
 //==========================================================================
 // This installs the int9 vector and initializes the keyboard in buffered
 // ASCII mode. key_close simply undoes that.
@@ -55,7 +57,7 @@ extern array<unsigned char, KEY_BUFFER_SIZE> unicode_frame_buffer;
 extern void key_flush();    // Clears the 256 char buffer
 extern int event_key_get(const d_event &event);	// Get the keycode from the EVENT_KEY_COMMAND event
 extern int event_key_get_raw(const d_event &event);	// same as above but without mod states
-extern unsigned char key_ascii();
+unsigned char key_ascii();
 
 class pressed_keys
 {
@@ -224,4 +226,6 @@ struct key_props
 
 extern const array<key_props, 256> key_properties;
 
+}
+
 #endif
diff --git a/common/include/mouse.h b/common/include/mouse.h
index 1c3e571e6..787e4cf68 100644
--- a/common/include/mouse.h
+++ b/common/include/mouse.h
@@ -23,6 +23,8 @@
 struct SDL_MouseButtonEvent;
 struct SDL_MouseMotionEvent;
 
+inline namespace dcx {
+
 #define MOUSE_MAX_BUTTONS       16
 #define Z_SENSITIVITY		100
 #define MBTN_LEFT		0
@@ -87,4 +89,6 @@ static inline void event_mouse_get_delta(const d_event &event, int *dx, int *dy,
 	*dz = e.dz;
 }
 
+}
+
 #endif
diff --git a/common/include/rbaudio.h b/common/include/rbaudio.h
index d574e35e6..ed8f83c29 100644
--- a/common/include/rbaudio.h
+++ b/common/include/rbaudio.h
@@ -17,14 +17,12 @@ AND AGREES TO THE TERMS HEREIN AND ACCEPTS THE SAME BY USE OF THIS FILE.
 COPYRIGHT 1993-1999 PARALLAX SOFTWARE CORPORATION.  ALL RIGHTS RESERVED.
 */
 
-
-
-#ifndef _RBAUDIO_H
-#define _RBAUDIO_H
+#pragma once
 
 #define RBA_MEDIA_CHANGED	-1
 
 #ifdef __cplusplus
+inline namespace dcx {
 
 struct RBACHANNELCTL
 {
@@ -74,6 +72,5 @@ unsigned long RBAGetDiscID();
 // List the tracks on the CD
 void RBAList(void);
 
-#endif
-
+}
 #endif
diff --git a/common/include/timer.h b/common/include/timer.h
index 440a0560a..8cf7e960e 100644
--- a/common/include/timer.h
+++ b/common/include/timer.h
@@ -16,6 +16,7 @@
 #include "maths.h"
 
 #ifdef __cplusplus
+inline namespace dcx {
 
 fix64 timer_update();
 __attribute_warn_unused_result
@@ -31,4 +32,5 @@ static inline void timer_delay2(int fps)
 	timer_delay_bound(1000u / fps);
 }
 
+}
 #endif
diff --git a/common/include/window.h b/common/include/window.h
index b3bcf31ca..4cc4d8382 100644
--- a/common/include/window.h
+++ b/common/include/window.h
@@ -21,6 +21,7 @@
 
 #ifdef __cplusplus
 #include "fwd-window.h"
+inline namespace dcx {
 
 enum class window_event_result : uint8_t
 {
@@ -83,4 +84,5 @@ static inline window_event_result (WINDOW_SEND_EVENT)(window &w, const d_event &
 	return window_send_event(w, event);
 }
 
+}
 #endif
diff --git a/common/main/kconfig.h b/common/main/kconfig.h
index 8cb0a5e8b..19a308aaa 100644
--- a/common/main/kconfig.h
+++ b/common/main/kconfig.h
@@ -30,11 +30,10 @@ COPYRIGHT 1993-1999 PARALLAX SOFTWARE CORPORATION.  ALL RIGHTS RESERVED.
 
 #ifdef __cplusplus
 #include <vector>
+#include "fwd-event.h"
 #include "compiler-array.h"
 #include "compiler-type_traits.h"
 
-struct d_event;
-
 #if defined(DXX_BUILD_DESCENT_I) || defined(DXX_BUILD_DESCENT_II)
 struct control_info {
 	template <typename T>