autotools - 在 autotools 中，什么是 dnl'ed？

Question

我在 autoconf 代码中看到很多关于被 dnl'ed 而不是 dnl'ed 的东西。什么是dnl？

Answer 1

来自 GNU M4 1.4.13 macro processor手动的:

8.1 Deleting whitespace in input

The builtin dnl stands for “Discard to Next Line”:

— Builtin: dnl

All characters, up to and including the next newline, are discarded without performing any macro expansion. A warning is issued if the end of the file is encountered without a newline.

The expansion of dnl is void.

它经常与 define 一起使用, 删除调用 define 之后的换行符.因此

   define(`foo', `Macro `foo'.')dnl A very simple macro, indeed.
   foo
   ⇒Macro foo.

与处理注释的方式相反(参见 Comments)，丢弃直到并包括下一个换行符的输入。

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