c - 转义换行符是 POSIX make 的一部分吗？

Question

POSIX make标准页面有关于转义换行符的说法(强调我的):

The treatment of escaped s throughout the makefile is historical practice. For example, the inference rule:

.c.o\
:

works, and the macro:

f=  bar baz\
   biz
a:
   echo ==$f==

echoes "==bar baz biz==".

“历史实践”是什么意思？

我是否可以在严格符合 POSIX makefile 中使用转义换行符？

Answer 1

POSIX 标准对转义换行符有这样的规定(这是在实际的标准文本中，而不是在信息部分或理性部分中):

When an escaped <newline> (one preceded by a <backslash>) is found anywhere in the makefile except in a command line, an include line, or a line immediately preceding an include line, it shall be replaced, along with any leading white space on the following line, with a single <space>. When an escaped <newline> is found in a command line in a makefile, the command line shall contain the <backslash>, the <newline>, and the next line, except that the first character of the next line shall not be included if it is a <tab>. When an escaped <newline> is found in an include line or in a line immediately preceding an include line, the behavior is unspecified.

这是您在转义换行符方面所依赖的 POSIX 强制行为。