Tweaked the debug building and printing a little - I hope this works OK for everyone. Let me know if not.

Tamped down a few warnings.
For the demo/server Makefile, made an either/or choice between executable size optimization (normal) or gdb debug info and no optimization.

bacnet-stack/demo/epics/Makefile

@@ -41,7 +41,7 @@ DEBUGGING =
 OPTIMIZATION = -Os
 ifeq (${BUILD},debug)
 OPTIMIZATION = -O0
-DEBUGGING = -g
+DEBUGGING = -g -DDEBUG_ENABLED=1
 endif
 # put all the flags together
 CFLAGS = -Wall $(DEBUGGING) $(OPTIMIZATION) $(INCLUDES) $(DEFINES)

bacnet-stack/demo/epics/main.c

@@ -903,7 +903,7 @@ int main(
     bool found = false;
     BACNET_OBJECT_ID myObject;
     uint8_t buffer[MAX_PDU] = { 0 };
-    BACNET_READ_ACCESS_DATA *rpm_object;
+    BACNET_READ_ACCESS_DATA *rpm_object = NULL;
     KEY nextKey;
 
     CheckCommandLineArgs(argc, argv);   /* Won't return if there is an issue. */

bacnet-stack/demo/server/Makefile

@@ -37,19 +37,27 @@ LIBRARY1=-L$(BACNET_LIB_DIR),-l$(BACNET_LIB_NAME)
 LIBRARY2=-lws2_32,-lgcc,-lm,-liphlpapi,-lwinmm
 LIBRARIES=$(LIBRARY1),$(LIBRARY2)
 endif
+
 #build for release (default) or debug
-DEBUGGING =
-OPTIMIZATION = -Os
 ifeq (${BUILD},debug)
+# Use -g to put info for gdb in the executable
+DEBUGGING = -g -DDEBUG_ENABLED=1
 OPTIMIZATION = -O0
-DEBUGGING = -g
+LINK_OPTIMIZATION = 
 ifeq (${BACDL_DEFINE},-DBACDL_BIP=1)
 DEFINES += -DBIP_DEBUG
 endif
+else 
+DEBUGGING =
+# Use -f optimizations and then link option --gc-sections to reduce executable size.
+# Of course, not when you want debug output for gdb!
+OPTIMIZATION = -Os -fdata-sections -ffunction-sections
+LINK_OPTIMIZATION = -Wl,--gc-sections
 endif
+
 # put all the flags together
-CFLAGS = -Wall $(DEBUGGING) $(OPTIMIZATION) $(INCLUDES) $(DEFINES) -fdata-sections -ffunction-sections
+CFLAGS = -Wall $(DEBUGGING) $(OPTIMIZATION) $(INCLUDES) $(DEFINES) 
-LFLAGS = -Wl,-Map=$(TARGET).map,$(LIBRARIES),--gc-sections
+LFLAGS = -Wl,-Map=$(TARGET).map,$(LIBRARIES) $(LINK_OPTIMIZATION)
 
 SRCS = main.c
 

bacnet-stack/include/debug.h

@@ -43,16 +43,19 @@
 extern "C" {
 #endif /* __cplusplus */
 
-#if DEBUG_ENABLED
     void debug_printf(
         const char *format,
         ...);
+#if DEBUG_ENABLED
+    /* Nothing more here */
 #else
-    static void debug_printf(
+    /* If your compiler supports it, this is more compact: 
+    inline void debug_printf(
         const char *format,
         ...) {
         format = format;
     }
+    */
 #endif
 #ifdef __cplusplus
 }

bacnet-stack/lib/Makefile

@@ -33,7 +33,7 @@ DEBUGGING =
 WARNINGS = -Wall -Wmissing-prototypes
 ifeq (${BUILD},debug)
 OPTIMIZATION = -O0
-DEBUGGING = -g
+DEBUGGING = -g -DDEBUG_ENABLED=1
 ifeq (${BACDL_DEFINE},-DBACDL_BIP=1)
 DEFINES += -DBIP_DEBUG
 endif

bacnet-stack/src/debug.c

@@ -55,4 +55,10 @@ void debug_printf(
 
     return;
 }
+#else
+void debug_printf(
+    const char *format,
+    ...) {
+    format = format;
+}
 #endif