linux - 如何在Makefile中测试CFLAGS中是否加入了某个符号？

Question

如果我在 Makefile 下面添加一行:

CFLAGS += -DMY_SYMBOL

如何测试子目录Makefile中是否定义了'MY_SYMBOL'？似乎以下不起作用:

ifdef MY_SYMBOL
#do something
endif

谢谢。

以下似乎也不起作用:

define symbol_in_cflags_check
@echo $(1)
@echo $(2)
ifeq ($(1), $(2))
SUBDIRS := music
endif
endef

RESULT := $(foreach SYMBOL, $(shell echo $(CFLAGS)), $(call symbol_in_cflags_check, $(SYMBOL), -DIN_MUSIC))

Answer 1

ifneq (,$(filter MY_SYMBOL,$(CFLAGS)))
# it is in CFLAGS, so do something
else
# it is NOT in CFLAGS, so do something else
endif