Fix build failures with `OPT = 0` due to inline functions (#19767)

Co-authored-by: Joel Challis <git@zvecr.com>

platforms/common.mk

@@ -2,6 +2,8 @@ PLATFORM_COMMON_DIR = $(PLATFORM_PATH)/$(PLATFORM_KEY)
 
 TMK_COMMON_SRC +=	\
 	$(PLATFORM_PATH)/suspend.c \
+	$(PLATFORM_PATH)/synchronization_util.c \
+	$(PLATFORM_PATH)/timer.c \
 	$(PLATFORM_COMMON_DIR)/hardware_id.c \
 	$(PLATFORM_COMMON_DIR)/platform.c \
 	$(PLATFORM_COMMON_DIR)/suspend.c \

platforms/synchronization_util.c

@@ -0,0 +1,17 @@
+// Copyright 2023 Sergey Vlasov (@sigprof)
+// SPDX-License-Identifier: GPL-2.0-or-later
+
+#include "synchronization_util.h"
+
+// Generate out-of-line copies for inline functions defined in synchronization_util.h.
+
+#if !defined(PLATFORM_SUPPORTS_SYNCHRONIZATION)
+#    if defined(SPLIT_KEYBOARD)
+extern inline void split_shared_memory_lock(void);
+extern inline void split_shared_memory_unlock(void);
+#    endif
+#endif
+
+#if defined(SPLIT_KEYBOARD)
+QMK_IMPLEMENT_AUTOUNLOCK_HELPERS(split_shared_memory)
+#endif

platforms/synchronization_util.h

@@ -29,6 +29,12 @@ inline void split_shared_memory_unlock(void){};
         prefix##_unlock();                                                  \
     }
 
+/* Generate an out-of-line implementation in case the inline functions defined
+ * by the above macro don't actually get inlined. */
+#define QMK_IMPLEMENT_AUTOUNLOCK_HELPERS(prefix)                  \
+    extern inline unsigned prefix##_autounlock_lock_helper(void); \
+    extern inline void     prefix##_autounlock_unlock_helper(unsigned* unused_guard);
+
 /* Convinience macro the automatically generate the correct RAII-style
  * lock_autounlock function macro */
 #define QMK_DECLARE_AUTOUNLOCK_CALL(prefix) unsigned prefix##_guard __attribute__((unused, cleanup(prefix##_autounlock_unlock_helper))) = prefix##_autounlock_lock_helper

platforms/timer.c

@@ -0,0 +1,8 @@
+// Copyright 2023 Sergey Vlasov (@sigprof)
+// SPDX-License-Identifier: GPL-2.0-or-later
+
+#include "timer.h"
+
+// Generate out-of-line copies for inline functions defined in timer.h.
+extern inline fast_timer_t timer_read_fast(void);
+extern inline fast_timer_t timer_elapsed_fast(fast_timer_t last);

quantum/mousekey.c

@@ -24,7 +24,7 @@
 #include "debug.h"
 #include "mousekey.h"
 
-inline int8_t times_inv_sqrt2(int8_t x) {
+static inline int8_t times_inv_sqrt2(int8_t x) {
     // 181/256 is pretty close to 1/sqrt(2)
     // 0.70703125                 0.707106781
     // 1 too small for x=99 and x=198