Makefile：创建函数会导致错误

Question

我的程序接收命令行参数。

我希望我的 Makefile 能够处理如下参数：

make run arg1 arg2 arg3

或

make debug arg1 arg2 arg3

在我的 Makefile 中，我使用这个答案中建议的方法。 第一个版本是

# Description of variables

# If the first argument is "run" or "debug"...
ifeq (run,$(firstword $(MAKECMDGOALS)))
        # use the rest as arguments for "run"
        ARGS := $(wordlist 2,$(words $(MAKECMDGOALS)),$(MAKECMDGOALS))
        # ...and turn them into do-nothing targets
        $(eval $(ARGS):;@:)
else ifeq (debug,$(firstword $(MAKECMDGOALS)))
        # use the rest as arguments for "run"
        ARGS := $(wordlist 2,$(words $(MAKECMDGOALS)),$(MAKECMDGOALS))
        # ...and turn them into do-nothing targets
        $(eval $(ARGS):;@:)
endif

all: $(EXECUTABLE)

# The rest of the Makefile

效果很好。

为了消除代码重复，我决定描述该函数

parse_args

：

# Description of variables

# Function to parse command line arguments
define parse_args
        # Extract the rest of the arguments after the first one
        $(eval ARGS := $(wordlist 2,$(words $(MAKECMDGOALS)),$(MAKECMDGOALS)))
        # ...and turn them into do-nothing targets
        $(eval $(ARGS):;@:)
endef

# If the first argument is "run" or "debug"...
ifeq (run,$(firstword $(MAKECMDGOALS)))
        $(call parse_args)
else ifeq (debug,$(firstword $(MAKECMDGOALS)))
        $(call parse_args)
endif

# The rest of the Makefile

但是这个版本的代码会产生错误：

:~/c/database_binary_and_hash_search$ make debug file add apple
Makefile:109: *** recipe commences before first target.  Stop.

也许有人可以解释为什么代码会这样？

Answer 1

也许有人可以解释为什么代码会这样？

恐怕这是一个乏味的解释。一旦

make

看到一行开始 使用选项卡时，它会认为该行位于配方上下文中，并且您有选项卡 您不希望

make

出现在菜谱上下文中。 这个答案 可能误导了您，因为它有双空格缩进，但实际上不是制表符。 像这样重写来解决这个问题：

$ cat Makefile
# Function to parse command line arguments
define parse_args
# Extract the rest of the arguments after the first one
$(eval ARGS := $(wordlist 2,$(words $(MAKECMDGOALS)),$(MAKECMDGOALS)))
$(eval $(ARGS):;@:))
endef

# If the first argument is "run" or "debug"...
ifeq (run,$(firstword $(MAKECMDGOALS)))
$(call $(parse_args))
else ifeq (debug,$(firstword $(MAKECMDGOALS)))
$(call $(parse_args))
endif

.PHONY: run debug

run:
    @echo running with args $(ARGS)
    
debug:
    @echo debugging with args $(ARGS)
    

这给你：

$ make run a b c
running with args a b c
$ make debug x y z
debugging with args x y z
$ make
running with args
$ make debug
debugging with args
$ make x
make: *** No rule to make target 'x'. Stop.