如果您只是想要一些输出，则需要单独使用$(info)。你可以在Makefile的任何地方这样做，它会显示这一行何时被求值:

$(info VAR="$(VAR)")

将输出VAR="<值的VAR>"每当make处理该行。这种行为非常依赖于位置，所以你必须确保$(info)展开发生在所有可以修改$(VAR)的事情已经发生之后!

一个更通用的选项是创建一个特殊的规则来打印变量的值。一般来说，规则是在变量赋值之后执行的，因此这将显示实际使用的值。(尽管规则可以改变变量。)良好的格式将有助于阐明变量的设置，而$(flavor)函数将告诉您某个变量的类型。所以在这个规则中:

print-% : ; $(info $* is a $(flavor $*) variable set to [$($*)]) @true

$* expands to the stem that the % pattern matched in the rule. $($*) expands to the value of the variable whose name is given by by $*. The [ and ] clearly delineate the variable expansion. You could also use " and " or similar. $(flavor $*) tells you what kind of variable it is. NOTE: $(flavor) takes a variable name, and not its expansion. So if you say make print-LDFLAGS, you get $(flavor LDFLAGS), which is what you want. $(info text) provides output. Make prints text on its stdout as a side-effect of the expansion. The expansion of $(info) though is empty. You can think of it like @echo, but importantly it doesn't use the shell, so you don't have to worry about shell quoting rules. @true is there just to provide a command for the rule. Without that, make will also output print-blah is up to date. I feel @true makes it more clear that it's meant to be a no-op.

运行它，你得到

$ make print-LDFLAGS
LDFLAGS is a recursive variable set to [-L/Users/...]

如果我想查看变量值，我通常会返回一个错误。(除非你想看看价值。它将停止执行。)

@echo $(NDK_PROJECT_PATH = $(NDK_PROJECT_PATH))

运行make -n;它告诉你变量的值。

Makefile……

all:
        @echo $(NDK_PROJECT_PATH)

命令:

export NDK_PROJECT_PATH=/opt/ndk/project
make -n 

输出:

echo /opt/ndk/project

你可以在读取makefile时打印出变量(假设你已经适当地标记了这个问题)，使用这个方法(使用一个名为“var”的变量):

$(info $$var is [${var}])

你可以把这个构造添加到任何recipe中，看看make会传递给shell什么:

.PHONY: all
all: ; $(info $$var is [${var}])echo Hello world

现在，这里发生的事情是，make将整个食谱($(info $$var is [${var}])echo Hello world)存储为一个递归展开的变量。当make决定运行配方时(例如，当您告诉它构建所有时)，它展开变量，然后将每一行结果分别传递给shell。

所以，在痛苦的细节中:

它扩展$(info $$var is [${var}])echo Hello world 为此，首先展开$(info $$var is [${var}]) $$变成字面上的$ ${var}变成:-)(说) 副作用是$var is[:-)]出现在标准输出 $(info…)的展开为空 Make留下echo Hello world 首先让打印在stdout上echo Hello world，让你知道它将要求shell做什么 shell在stdout上输出Hello world。

如果您只是想要一些输出，则需要单独使用$(info)。你可以在Makefile的任何地方这样做，它会显示这一行何时被求值:

$(info VAR="$(VAR)")

将输出VAR="<值的VAR>"每当make处理该行。这种行为非常依赖于位置，所以你必须确保$(info)展开发生在所有可以修改$(VAR)的事情已经发生之后!

一个更通用的选项是创建一个特殊的规则来打印变量的值。一般来说，规则是在变量赋值之后执行的，因此这将显示实际使用的值。(尽管规则可以改变变量。)良好的格式将有助于阐明变量的设置，而$(flavor)函数将告诉您某个变量的类型。所以在这个规则中:

print-% : ; $(info $* is a $(flavor $*) variable set to [$($*)]) @true

$* expands to the stem that the % pattern matched in the rule. $($*) expands to the value of the variable whose name is given by by $*. The [ and ] clearly delineate the variable expansion. You could also use " and " or similar. $(flavor $*) tells you what kind of variable it is. NOTE: $(flavor) takes a variable name, and not its expansion. So if you say make print-LDFLAGS, you get $(flavor LDFLAGS), which is what you want. $(info text) provides output. Make prints text on its stdout as a side-effect of the expansion. The expansion of $(info) though is empty. You can think of it like @echo, but importantly it doesn't use the shell, so you don't have to worry about shell quoting rules. @true is there just to provide a command for the rule. Without that, make will also output print-blah is up to date. I feel @true makes it more clear that it's meant to be a no-op.

运行它，你得到

$ make print-LDFLAGS
LDFLAGS is a recursive variable set to [-L/Users/...]

如果你使用android make (mka) @echo $(NDK_PROJECT_PATH)将不起作用，并给你错误***丢失分隔符。停止。” 如果你想在android make中打印变量，请使用这个答案

NDK_PROJECT_PATH := some_value
$(warning $(NDK_PROJECT_PATH))

这对我很有用