如何在make变量/函数中使用多个空格？

Question

通常，make组合多个连续的空格字符。有时这种行为是不需要的。对于这种情况，这是示例：

.PHONY: help

help:
    $(info Usage: make [command] [VARIABLES])
    $(info )
    $(info command1 ..... Do what command1 does and)
    $(info                let the sentence continue.)
    $(info command2 ..... Description of command2)

通缉输出：

Usage: make [command] [VARIABLES]

command1 ..... Do what command1 does and
               let the sentence continue.
command2 ..... Description of command2

实际输出：

Usage: make [command] [VARIABLES]

command1 ..... Do what command1 does and
 let the sentence continue.                 # Not aligned with "Do" in line above
command2 ..... Description of command2

换句话说，有没有办法在make中对齐或引用空格？

Answer 1

有一个老技巧：

EMPTY=
SPACE=$(EMPTY) $(EMPTY)

所以，在你的情况下：

.PHONY: help

EMPTY=
SPACE=$(EMPTY) $(EMPTY)

help:
    $(info Usage: make [command] [VARIABLES])
    $(info )
    $(info command1 ..... Do what command1 does and)
    $(info $(SPACE)$(SPACE)$(SPACE)$(SPACE)$(SPACE)$(SPACE)$(SPACE)$(SPACE)$(SPACE)$(SPACE)$(SPACE)$(SPACE)$(SPACE)$(SPACE)$(SPACE)let the senten\
ce continue.)
    $(info command2 ..... Description of command2)

Answer 2

第一个想法：不要在配方中使用$(info ...)。而是使用像echo等shell命令。然后你可以使用引用等来保留空格。

第二个想法，使用define变量定义来包含完整的内容：

define USAGE
Usage: make [command] [VARIABLES]

command1 ..... Do what command1 does and
               let the sentence continue.
command2 ..... Description of command2
endef

.PHONY: help
help: ; $(info $(value USAGE))