Makefile 忽略模式中子目录的模式规则

Question

考虑以下目录结构:

.
  bar/
    foo/
      test.ext1
  _foo/

我用以下规则编写了一个makefile:

_%.ext2: bar/%.ext1 # % should match foo/test
    echo $*

但是正在运行 make _foo/test.ext2给出:

make: *** No rule to make target '_foo/test.ext2'.  Stop.

当我看着 make -d _foo/test.ext2 ，它甚至不考虑上述规则，即它直接跳转到尝试内置规则。我不明白这里发生了什么，所以有人可以向我解释一下吗？

编辑:
我希望能够从 bar 中的任意文件生成，例如:

bar/foo/test-2.ext1 -> _foo/test-2.ext2

bar/baz/another.ext1 -> _baz/another.ext2

等

_foo的存在和 _baz是有保证的。

Answer 1

这在 manual 中有解释:

When the target pattern does not contain a slash (and it usually does not), directory names in the file names are removed from the file name before it is compared with the target prefix and suffix.

和

When prerequisites are turned into file names, the directories from the stem are added at the front, while the rest of the stem is substituted for the %

因此，使用类似 _%.ext2 的模式下划线与文件名匹配，而不是目录名。所以它不匹配 _foo/test.ext2但它会匹配 foo/_test.ext2 (并寻找 foo/bar/test.ext1 )。你自己看:

$ cat Makefile
_%.ext2: bar/%.ext1
        echo Making $@ from $<

$ make -dr _foo/test.ext2
...
Considering target file '_foo/test.ext2'.
 File '_foo/test.ext2' does not exist.
 Looking for an implicit rule for '_foo/test.ext2'.
 No implicit rule found for '_foo/test.ext2'.
 Finished prerequisites of target file '_foo/test.ext2'.
Must remake target '_foo/test.ext2'.
make: *** No rule to make target '_foo/test.ext2'.  Stop.

$ make -dr foo/_test.ext2
...
Considering target file 'foo/_test.ext2'.
 File 'foo/_test.ext2' does not exist.
 Looking for an implicit rule for 'foo/_test.ext2'.
 Trying pattern rule with stem 'test'.
 Trying implicit prerequisite 'foo/bar/test.ext1'.
 Trying pattern rule with stem 'test'.
 Trying implicit prerequisite 'foo/bar/test.ext1'.
 Looking for a rule with intermediate file 'foo/bar/test.ext1'.
  Avoiding implicit rule recursion.
 No implicit rule found for 'foo/_test.ext2'.
 Finished prerequisites of target file 'foo/_test.ext2'.
Must remake target 'foo/_test.ext2'.
make: *** No rule to make target 'foo/_test.ext2'.  Stop.

修复它的最简单方法是使目标包含斜杠。如果您可以将输出移动到其他地方，则可以执行以下操作:

$ cat Makefile
OBJDIR := obj
$(OBJDIR)/_%.ext2: bar/%.ext1
        echo Making $@ from $<

$ make obj/_foo/test.ext2
echo Making obj/_foo/test.ext2 from bar/foo/test.ext1
Making obj/_foo/test.ext2 from bar/foo/test.ext1

甚至

$ cat Makefile
_/%.ext2: bar/%.ext1
        echo Making $@ from $<

$ make _/foo/test.ext2
echo Making _/foo/test.ext2 from bar/foo/test.ext1
Making _/foo/test.ext2 from bar/foo/test.ext1

如果您不能这样做，您可以尝试通过完整路径进行引用，即:

$ cat Makefile
$(CURDIR)/_%.ext2: bar/%.ext1
        echo Making $@ from $<

$ make $(pwd)/_foo/test.ext2
echo Making /path/to/curdir/_foo/test.ext2 from bar/foo/test.ext1
Making /path/to/curdir/_foo/test.ext2 from bar/foo/test.ext1

请注意，使用 ./不起作用，因为 GNU make strips 领先 ./来自使模式再次不匹配的目标:

$ cat Makefile
./_%.ext2: bar/%.ext1
        echo Making $@ from $<

$ make -dr ./_foo/test.ext2
...
Considering target file '_foo/test.ext2'.
 File '_foo/test.ext2' does not exist.
 Looking for an implicit rule for '_foo/test.ext2'.
 No implicit rule found for '_foo/test.ext2'.
 Finished prerequisites of target file '_foo/test.ext2'.
Must remake target '_foo/test.ext2'.
make: *** No rule to make target '_foo/test.ext2'.  Stop.

如果你想让你的同行评审同事紧张，你也可以使用一些二次扩展魔法来生成正确的先决条件名称，例如:

$ cat Makefile
percent := %
.SECONDEXPANSION:
%.ext2: bar/$$(patsubst _$$(percent),$$(percent),$$(@D))/$$*.ext1
        echo Making $@ from $<

$ make _foo/test.ext2
echo Making _foo/test.ext2 from bar/foo/test.ext1
Making _foo/test.ext2 from bar/foo/test.ext1

注: %必须通过 $(percent) 引用变量，否则 GNU make 解析器可能会提示或误解 patsubst功能。

您的 final方法有效，因为您的最终解决方案是静态模式规则。它不应用相同的“ strip 目录”方法，而只是匹配字符串。