[修改] export导出的变量的副本，子makefile修改变量不上层

.editorconfig

@@ -1,14 +0,0 @@
-# EditorConfig is awesome: https://EditorConfig.org
-
-# top-most EditorConfig file
-root = true
-
-[*]
-end_of_line = lf
-charset     = utf-8
-
-[Makefile]
-indent_style = tab
-indent_size  = 8
-trim_trailing_whitespace = false
-insert_final_newline     = false

01-Variable_MAKEFILE_LIST/Makefile

@@ -1,11 +0,0 @@
-
-makedir := $(abspath $(lastword $(MAKEFILE_LIST)))
-$(warning makedir1=$(makedir))
-
-include dir1/Makefile
-
-makedir := $(abspath $(lastword $(MAKEFILE_LIST)))
-$(warning makedir3=$(makedir))
-
-all:
-	@echo "Completing the main Makefile"

01-Variable_MAKEFILE_LIST/dir1/Makefile

@@ -1,6 +0,0 @@
-
-
-makedir := $(abspath $(lastword $(MAKEFILE_LIST)))
-$(warning makedir2=$(makedir))
-
-

02-Test_set_after_reference/Makefile

@@ -1,10 +0,0 @@
-
-PUBLIC_INCVPATH += $(PROJECT_ROOT)/public
-$(warning "PUBLIC_INCVPATH : $(PUBLIC_INCVPATH), with PROJECT_ROOT not set")
-
-PROJECT_ROOT:=$(CURDIR)
-
-$(warning "PUBLIC_INCVPATH : $(PUBLIC_INCVPATH), with PROJECT_ROOT set")
-
-all:
-	@echo "This is a dummy target to ensure the Makefile is valid."

Makefile

@@ -0,0 +1,8 @@
+
+var_a = a
+
+export var_a 
+
+all:
+	make -C dir1
+	echo "Get var_a=$(var_a)"

dir1/Makefile

@@ -0,0 +1,8 @@
+
+
+$(warning var_a=$(var_a))
+var_a = b
+
+all:
+	echo "set var_a=b"
+