message: Define _LIBCPP_DEBUG in debug builds
  This macro is used to enable assertions and iterator debugging checks
  within libc++
diff: @@ -115,7 +115,7 @@ endif
  ifeq ($(CFG), debug)
  ODIR=_debug
  CFLAGS += -O0 -DDEBUG
  - CFLAGS += -D_GLIBCXX_DEBUG -D_GLIBCXX_DEBUG_PEDANTIC -D_GLIBCXX_SANITIZE_VECTOR
  + CFLAGS += -D_GLIBCXX_DEBUG -D_GLIBCXX_DEBUG_PEDANTIC -D_GLIBCXX_SANITIZE_VECTOR -D_LIBCPP_DEBUG=1
  else
  ODIR=_release
  CFLAGS += -O2 -DNDEBUG
  