GNU make manual 翻译( 一百七十九)

最新推荐文章于 2020-05-17 16:54:10 发布

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#操作系统

本文详细介绍了Makefile中如何使用条件式进行编译，并通过示例解释了文本层面的工作原理，展示了不同条件下makefile规则的变化。

继续翻译

   As this example illustrates, conditionals work at the textual level:
the lines of the conditional are treated as part of the makefile, or
ignored, according to the condition.  This is why the larger syntactic
units of the makefile, such as rules, may cross the beginning or the
end of the conditional.

   When the variable `CC' has the value `gcc', the above example has
this effect:

     foo: $(objects)
             $(CC) -o foo $(objects) $(libs_for_gcc)

When the variable `CC' has any other value, the effect is this:

     foo: $(objects)
             $(CC) -o foo $(objects) $(normal_libs)

   Equivalent results can be obtained in another way by
conditionalizing a variable assignment and then using the variable
unconditionally:

     libs_for_gcc = -lgnu
     normal_libs =

     ifeq ($(CC),gcc)
       libs=$(libs_for_gcc)
     else
       libs=$(normal_libs)
     endif

     foo: $(objects)
             $(CC) -o foo $(objects) $(libs)