为什么 GNU Make 罐头食谱不起作用？

Question

我期望看到由下面的 makefile 创建的文件 foo1 和 foo3。但是，仅创建了一个文件 foo3。对我来说，罐头食谱 make-foo 似乎被 make 忽略了。目标 foo1 和 foo2（空配方）的调试结果是相同的。

# why canned recipe doesn't work ?
# http://www.gnu.org/software/make/manual/make.html#Canned-Recipes
define make-foo =
echo making $@
touch $@
endef

.PHONY: all
all: foo1 foo2 foo3

# foo1 is not created, but why ?
.PHONY: foo1
foo1:
    $(make-foo)

# debug output similar to foo1
.PHONY: foo2
foo2:

# this works
.PHONY: foo3
foo3:
    echo making $@
    touch $@

运行 make：

xxxx@xxxx:/dev/shm$ make -dRr
GNU Make 3.81
Copyright (C) 2006  Free Software Foundation, Inc.
This is free software; see the source for copying conditions.
There is NO warranty; not even for MERCHANTABILITY or FITNESS FOR A
PARTICULAR PURPOSE.

This program built for i686-pc-linux-gnu
Reading makefiles...
Reading makefile `makefile'...
Updating makefiles....
 Considering target file `makefile'.
  Looking for an implicit rule for `makefile'.
  No implicit rule found for `makefile'.
  Finished prerequisites of target file `makefile'.
 No need to remake target `makefile'.
Updating goal targets....
Considering target file `all'.
 File `all' does not exist.
  Considering target file `foo1'.
   File `foo1' does not exist.
   Finished prerequisites of target file `foo1'.
  Must remake target `foo1'.
  Successfully remade target file `foo1'.
  Considering target file `foo2'.
   File `foo2' does not exist.
   Finished prerequisites of target file `foo2'.
  Must remake target `foo2'.
  Successfully remade target file `foo2'.
  Considering target file `foo3'.
   File `foo3' does not exist.
   Finished prerequisites of target file `foo3'.
  Must remake target `foo3'.
echo making foo3
Putting child 0x0914c5f0 (foo3) PID 3132 on the chain.
Live child 0x0914c5f0 (foo3) PID 3132 
making foo3
Reaping winning child 0x0914c5f0 PID 3132 
touch foo3
Live child 0x0914c5f0 (foo3) PID 3133 
Reaping winning child 0x0914c5f0 PID 3133 
Removing child 0x0914c5f0 PID 3133 from chain.
  Successfully remade target file `foo3'.
 Finished prerequisites of target file `all'.
Must remake target `all'.
Successfully remade target file `all'.

缺少 foo1：

xxxx@xxxx:/dev/shm$ ll foo*
-rw-r--r-- 1 xxxx xxxx 0 2011-02-17 20:04 foo3

Answer 1

我认为您不希望在 define 行末尾添加 = 。这个 makefile 在这里对我有用：

define make-foo
echo making $@
touch $@
endef

.PHONY: foo1
foo1:
    $(make-foo)

示例：

$ make
echo making foo1
making foo1
touch foo1
$ ls
Makefile  foo1

GNU make 手册 似乎表明 = 应该没问题，但像你一样，如果我有它，我会得到不同的行为。

编辑：我刚刚问：

GNU 在多行变量声明中做出差异

澄清一下这里发生的事情......