makefile - 不执行虚假目标的配方

Question

考虑从 GNU make 手册中摘录的 PHONY 目标:

Once this is done, make clean' will run the commands regardless of whether there is a file namedclean'.

为什么我没有看到我的食谱被执行，尽管在调试输出中 make 说它必须重新制作这些目标？下面是一个示例 makefile 来演示该问题:

all:
    @echo Rule to build 'all'

.PHONY: clean a.clean b.clean
clean: a.clean b.clean
    @echo Cleaning toplevel

%.clean:
    @echo Cleaning $*

这是输出 - 注意没有提到 Cleaning $*

make: Entering directory `/tmp'
Cleaning toplevel
make: Leaving directory `/tmp'

这是 -d 的输出:

Considering target file `clean'.
 File `clean' does not exist.
  Considering target file `a.clean'.
   File `a.clean' does not exist.
   Finished prerequisites of target file `a.clean'.
  Must remake target `a.clean'.
 Successfully remade target file `a.clean'.
  Considering target file `b.clean'.
   File `b.clean' does not exist.
   Finished prerequisites of target file `b.clean'.
  Must remake target `b.clean'.
  Successfully remade target file `b.clean'.
 Finished prerequisites of target file `clean'.
Must remake target `clean'.

Answer 1

来自 the same section of the manual :

因为它知道假目标不会命名可以从其他文件重新制作的实际文件，make 会跳过隐式规则搜索假目标(请参阅隐式规则)。

是的，Make 知道它必须“重新制作”a.clean 和 b.clean，但是在寻找这样做的规则时，它不会考虑您的模式规则。它找不到这些目标的配方，所以它耸了耸肩，认为工作完成并继续前进。

您可以通过将模式规则设为静态 模式规则来解决此问题:

a.clean b.clean : %.clean :
    @echo Cleaning $*