Makefile 条件 OR 定义

发布于 2025-01-12 02:00:06 字数 278 浏览 4 评论 0原文

我有一个带有 2 个 ifdef 条件的 Makefile，当选择该特定配置时，它们执行相同的操作。

     #ifdef A
     //perform C
     #endif /* A */

     #ifdef B
     //perform C
     #endif /* B */

     #ifdef A || B
     //perform C
     #endif

最后一个代码块不起作用。在 Makefile 中执行它的正确方法是什么？

原文

I have a Makefile with 2 ifdef conditions that perform same action when that particular config is selected.

     #ifdef A
     //perform C
     #endif /* A */

     #ifdef B
     //perform C
     #endif /* B */

     #ifdef A || B
     //perform C
     #endif

Last code block is not working. What is the right way to execute it in Makefile?

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得不到的就毁灭 2025-01-19 02:00:06

#ifdef 和 #endif 不是 make 条件。您可能想要：

ifdef A
# whatever if make variable A is defined
AB := defined
endif

ifdef B
# whatever if make variable B is defined
AB := defined
endif

ifeq ($(AB),defined)
# whatever if the make variable A or B is defined
endif

请注意，ifdef A 与 ifneq ($(A),) 不同。因此，如果您想测试这些变量不是为了定义而是为了空性，您可能需要：

ifneq ($(A),)
# whatever if the value of make variable A is non-empty
endif

ifneq ($(B),)
# whatever if the value of make variable B is non-empty
endif

ifneq ($(A)$(B),)
# whatever if the value of make variable A or B is non-empty
endif

#ifdef and #endif are not make conditionals. You probably want:

ifdef A
# whatever if make variable A is defined
AB := defined
endif

ifdef B
# whatever if make variable B is defined
AB := defined
endif

ifeq ($(AB),defined)
# whatever if the make variable A or B is defined
endif

Note that ifdef A is not the same as ifneq ($(A),). So, if you want to test these variables not for definition but for emptiness, you probably want:

ifneq ($(A),)
# whatever if the value of make variable A is non-empty
endif

ifneq ($(B),)
# whatever if the value of make variable B is non-empty
endif

ifneq ($(A)$(B),)
# whatever if the value of make variable A or B is non-empty
endif

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逆流 2025-01-19 02:00:06

这是使用我在评论中提出的技术变体的一种方法：

# De Morgan's Law: (!a && !b) == !(a || b)
ifndef A
  ifndef B
    NEITHER_A_NOR_B_DEFINED :=
  endif
endif

ifndef NEITHER_A_NOR_B_DEFINED
  # Perform C
endif

Here's one way to do it using a variant of the technique I proposed in a comment:

# De Morgan's Law: (!a && !b) == !(a || b)
ifndef A
  ifndef B
    NEITHER_A_NOR_B_DEFINED :=
  endif
endif

ifndef NEITHER_A_NOR_B_DEFINED
  # Perform C
endif

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