Use SdFatUtil::FreeRam() for freeMemory() if there

Marlin/Marlin_main.cpp

@@ -402,7 +402,11 @@ void serial_echopair_P(const char *s_P, double v)
 void serial_echopair_P(const char *s_P, unsigned long v)
     { serialprintPGM(s_P); SERIAL_ECHO(v); }
 
-extern "C"{
+#ifdef SDSUPPORT
+  #include "SdFatUtil.h"
+  int freeMemory() { return SdFatUtil::FreeRam(); }
+#else
+  extern "C" {
     extern unsigned int __bss_end;
     extern unsigned int __heap_start;
     extern void *__brkval;
@@ -410,14 +414,15 @@ extern "C"{
     int freeMemory() {
       int free_memory;
 
-    if((int)__brkval == 0)
+      if ((int)__brkval == 0)
         free_memory = ((int)&free_memory) - ((int)&__bss_end);
       else
         free_memory = ((int)&free_memory) - ((int)__brkval);
 
       return free_memory;
     }
-}
+  }
+#endif //!SDSUPPORT
 
 //adds an command to the main command buffer
 //thats really done in a non-safe way.