请教Makefile中的一条代码

superlinux

PLATFORM_CPPFLAGS +=$(call cc-option,-mapcs-32,$(call cc-option,-mabi=apcs-gnu),)

上面这段代码等号右边是什么意思？

superlinux

楼上的这种回复真让我无奈啊，不过还是谢谢吧
我问的是$(call cc-option,-mapcs-32,$(call cc-option,-mabi=apcs-gnu),)这个是什么意思

MMMIX

原帖由 superlinux 于 2007-9-22 15:57 发表
楼上的这种回复真让我无奈啊，不过还是谢谢吧
我问的是$(call cc-option,-mapcs-32,$(call cc-option,-mabi=apcs-gnu),)这个是什么意思

哦，是我看岔了。这个你自己查文档吧， 这种问题实在没什么好问的。

cjaizss

摘自info make

The `call' Function
===================

   The `call' function is unique in that it can be used to create new
parameterized functions.  You can write a complex expression as the
value of a variable, then use `call' to expand it with different values.

   The syntax of the `call' function is:

     $(call VARIABLE,PARAM,PARAM,...)

   When `make' expands this function, it assigns each PARAM to
temporary variables `$(1)', `$(2)', etc.  The variable `$(0)' will
contain VARIABLE.  There is no maximum number of parameter arguments.
There is no minimum, either, but it doesn't make sense to use `call'
with no parameters.

   Then VARIABLE is expanded as a `make' variable in the context of
these temporary assignments.  Thus, any reference to `$(1)' in the
value of VARIABLE will resolve to the first PARAM in the invocation of
`call'.

   Note that VARIABLE is the _name_ of a variable, not a _reference_ to
that variable.  Therefore you would not normally use a `$' or
parentheses when writing it.  (You can, however, use a variable
reference in the name if you want the name not to be a constant.)

   If VARIABLE is the name of a builtin function, the builtin function
is always invoked (even if a `make' variable by that name also exists).

   The `call' function expands the PARAM arguments before assigning
them to temporary variables.  This means that VARIABLE values
containing references to builtin functions that have special expansion
rules, like `foreach' or `if', may not work as you expect.

   Some examples may make this clearer.

   This macro simply reverses its arguments:

     reverse = $(2) $(1)

     foo = $(call reverse,a,b)

Here FOO will contain `b a'.

   This one is slightly more interesting: it defines a macro to search
for the first instance of a program in `PATH':

     pathsearch = $(firstword $(wildcard $(addsufix /$(1),$(subst :, ,$(PATH)))))

     LS := $(call pathsearch,ls)

Now the variable LS contains `/bin/ls' or similar.

   The `call' function can be nested.  Each recursive invocation gets
its own local values for `$(1)', etc. that mask the values of
higher-level `call'.  For example, here is an implementation of a "map"
function:

     map = $(foreach a,$(2),$(call $(1),$(a)))

   Now you can MAP a function that normally takes only one argument,
such as `origin', to multiple values in one step:

     o = $(call map,origin,o map MAKE)

   and end up with O containing something like `file file default'.

   A final caution: be careful when adding whitespace to the arguments
to `call'.  As with other functions, any whitespace contained in the
second and subsequent arguments is kept; this can cause strange
effects.  It's generally safest to remove all extraneous whitespace when
providing parameters to `call'.

摘自《跟我一起写Makefile》

六、call函数
call函数是唯一一个可以用来创建新的参数化的函数。你可以写一个非常复杂的表达式，这个表达式中，你可以定义许多参数，然后你可以用call函数来向这个表达式传递参数。其语法是：
$(call <expression>,<parm1>,<parm2>,<parm3>...)
当make执行这个函数时，<expression>参数中的变量，如$(1)，$(2)，$(3)等，会被参数<parm1>，<parm2>，<parm3>依次取代。而<expression>的返回值就是call函数的返回值。例如：
reverse = $(1) $(2)
foo = $(call reverse,a,b)
那么，foo的值就是“a b”。当然，参数的次序是可以自定义的，不一定是顺序的，如：
reverse = $(2) $(1)
foo = $(call reverse,a,b)
此时的foo的值就是“b a”。