makefile - 隐式规则先决条件中的通配符

Question

BUILT_DIR = /tmp/obj 
SRC = /source/dir  

/tmp/obj/%/builtin.o : $(SRC)/%/*.c
      gcc $^ -o $@

但是你知道:

In order for the pattern rule to apply, its target pattern must match the file name under consideration and all of its prerequisites (after pattern substitution) must name files that exist or can be made.

如果我执行 make/tmp/obj/hfa/builtin.o，make 会报错:

make: *** No rule to make target/tmp/obj/hfa/builtin.o'.停止。`

如何修改 Makefile 以满足我的要求？

Answer 1

可以使用二级扩展

BUILT_DIR = /tmp/obj 
SRC = /source/dir  
.SECONDEXPANSION:
/tmp/obj/%/builtin.o : $$(wildcard $(SRC)/%/*.c)
      gcc $^ -o $@