Makefile 忽略模式中包含子目录的模式规则

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 $*

然而运行 make _foo/test.ext2 给出：

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

当我查看 make -d _foo/test.ext2 时，它甚至没有考虑上述规则，即它直接跳转到尝试内置规则。我不明白这里发生了什么，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
等等

保证_foo和_baz存在。

Answer 1

规则 _%.ext2: bar/%.ext1，当在目标 _foo/test.ext2 上调用时，将匹配词干 (%) 等于 foo 的规则。要使规则生效，需要有一个文件（或规则）来创建 bar/%.ext1 = bar/foo.ext1.

根据 OP，输入文件是 bar/foo/test1.ext1.

尝试调整依赖关系：

_%/test.ext2: bar/%/test.ext1
    echo $*

Answer 2

我通过将以下内容添加到 makefile 中设法避免了这个问题：

TARGETS := $(patsubst bar/%,_%,$(patsubst %.ext1,%.ext2,$(wildcard bar/**/*.ext1)))

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

这基本上是预先构建目标（从 bar/ 中可用的文件），然后将规则应用于它们。但是，我不确定为什么模式规则适用于这种情况而不适用于原始情况，所以我仍然希望得到解释。

Answer 3

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，对于像 _%.ext2 这样的模式，下划线与文件名而不是目录名匹配。所以它不匹配 _foo/test.ext2 但它会匹配 foo/_test.ext2（并查找 foo/bar/test.ext1）。自己看看：

$ 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.

最简单的修复方法是让目标包含斜杠。如果你可以将输出移动到别处，你可以这样做：

$ 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

如果做不到，可以尝试全路径引用，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 从目标中生成前导 ./ 的条带，使模式再次不匹配：

$ 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适当的先决条件名称，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

注意：% 必须通过 $(percent) 变量引用，否则 GNU make 解析器可能会抱怨或误解 patsubst 函数。

您的最终方法有效，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 directory' 方法，而只是匹配字符串。

Makefile 忽略模式中包含子目录的模式规则

Makefile ignores pattern rule with subdirectory in pattern

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