通过命令行附加到GNU make变量

查看 override directive . 您可能需要修改makefile一次,但它应该做您想做的事情。

override CFLAGS += -Wall

app: main.c
    gcc $(CFLAGS) -o app main.c 

命令行示例:

$ make
gcc -Wall -o app main.c 
$ make CFLAGS=-g
gcc -g -Wall -o app main.c 

预备

我需要一种实际附加的方法,并提出:

override CFLAGS := -Wall $(CFLAGS)

有两种方法可以传递变量以生成:

• 使用命令行参数:

  make VAR=value
  

• 使用环境:

  export VAR=var; make
  

  或者(更好,因为它仅为当前命令更改环境)

  VAR=var make
  

它们略有不同。第一个更强。这意味着你知道你想要什么。第二种可能被认为是一种暗示。它们之间的区别在于运算符 = 和 += override

CC ?= gcc
CFLAGS += -Wall
INTERNAL_VARS = value

并称之为:

CFLAGS=-g make

注意,如果您想退出 -Wall

make CFLAGS=

请不要使用 推翻 推翻 .

只是一个便条,因为我感到困惑-让这个文件 testmake

$(eval $(info A: CFLAGS here is $(CFLAGS)))

override CFLAGS += -B

$(eval $(info B: CFLAGS here is $(CFLAGS)))

CFLAGS += -C

$(eval $(info C: CFLAGS here is $(CFLAGS)))

override CFLAGS += -D

$(eval $(info D: CFLAGS here is $(CFLAGS)))

CFLAGS += -E

$(eval $(info E: CFLAGS here is $(CFLAGS)))

然后:

$ make -f testmake
A: CFLAGS here is 
B: CFLAGS here is -B
C: CFLAGS here is -B
D: CFLAGS here is -B -D
E: CFLAGS here is -B -D
make: *** No targets.  Stop.
$ make -f testmake CFLAGS+=-g
A: CFLAGS here is -g
B: CFLAGS here is -g -B
C: CFLAGS here is -g -B
D: CFLAGS here is -g -B -D
E: CFLAGS here is -g -B -D
make: *** No targets.  Stop.

和 override 试做 文件:

$ make -f testmake
A: CFLAGS here is 
B: CFLAGS here is -B
C: CFLAGS here is -B -C
D: CFLAGS here is -B -C -D
E: CFLAGS here is -B -C -D -E
make: *** No targets.  Stop.
$ make -f testmake CFLAGS+=-g
A: CFLAGS here is -g
B: CFLAGS here is -g
C: CFLAGS here is -g
D: CFLAGS here is -g
E: CFLAGS here is -g
make: *** No targets.  Stop.

所以

• 推翻 一次,它只能附加另一个带有 推翻
• 当没有 推翻 完全试图附加(如在 += )从命令行覆盖该变量的每个实例。