makefile - 如何在 Makefile 中正确添加两个数字

Question

我想知道哪种解决方案更好地在 Makefile 中添加两个数字。就我而言，我将使用函数 add如下所示:

result = $(call add, 34, 56)
$(error $(result))                        

解决方案1:

add    = $(shell echo $$(( $(1) + $(2) )))

解决方案2:

add    = $(shell perl -e 'print $1 + $2')

解决方案3:

add    = $(shell echo '$1 + $2' | bc | tr '\n' ' ')

解决方案4:

16 := x x x x x x x x x x x x x x x
_input_int := $(foreach a,$(16),$(foreach b,$(16),$(foreach c,$(16),$(16)))))

_decode = $(words $1)
_encode = $(wordlist 1,$1,$(_input_int))
_plus = $1 $2
_max = $(subst xx,x,$(join $1,$2))

_push = $(eval stack := $$1 $(stack))
_pop = $(word 1,$(stack))$(eval stack := $(wordlist 2,$(words $(stack)),$(stack)))
_pope = $(call _encode,$(call _pop))
_pushd = $(call _push,$(call _decode,$1))

calculate=$(eval stack:=)$(foreach t,$1,$(call handle,$t))$(stack)
handle   =$(call _pushd,                                          \
            $(if $(filter +,$1),                                  \
              $(call _plus,$(call _pope),$(call _pope)),          \
                $(call _encode,$1)))

add     = $(strip $(foreach v,$(2), $(call calculate, $v $(1) +))) 

我承认解决方案 4 很荒谬，但它是唯一一个不依赖于诸如 bash 之类的外部工具的解决方案。 , perl或 bc .

Answer 1

试试 GNU Make Standard Library ，它提供整数算术函数。