rework structure

hifive1-vp/riscv-bldc-forced-commutation/bsp/libwrap/sys/sbrk.c

@@ -0,0 +1,18 @@
+/* See LICENSE of license details. */
+
+#include <stddef.h>
+#include "weak_under_alias.h"
+
+void *__wrap_sbrk(ptrdiff_t incr)
+{
+  extern char _end[];
+  extern char _heap_end[];
+  static char *curbrk = _end;
+
+  if ((curbrk + incr < _end) || (curbrk + incr > _heap_end))
+    return NULL - 1;
+
+  curbrk += incr;
+  return curbrk - incr;
+}
+weak_under_alias(sbrk);