diff --git a/make_helpers/build_macros.mk b/make_helpers/build_macros.mk
index 89f43f2..9ca6bdf 100644
--- a/make_helpers/build_macros.mk
+++ b/make_helpers/build_macros.mk
@@ -38,6 +38,18 @@
 $(eval uppercase_result:=$(call uppercase_internal,$(uppercase_table),$(1)))$(uppercase_result)
 endef
 
+# Convenience function for setting a variable to 0 if not previously set
+# $(eval $(call default_zero,FOO))
+define default_zero
+	$(eval $(1) ?= 0)
+endef
+
+# Convenience function for setting a list of variables to 0 if not previously set
+# $(eval $(call default_zeros,FOO BAR))
+define default_zeros
+	$(foreach var,$1,$(eval $(call default_zero,$(var))))
+endef
+
 # Convenience function for adding build definitions
 # $(eval $(call add_define,FOO)) will have:
 # -DFOO if $(FOO) is empty; -DFOO=$(FOO) otherwise
@@ -45,7 +57,6 @@
     DEFINES			+=	-D$(1)$(if $(value $(1)),=$(value $(1)),)
 endef
 
-
 # Convenience function for addding multiple build definitions
 # $(eval $(call add_defines,FOO BOO))
 define add_defines