如何在Makefile中定义C ++预处理器变量

Question

I have a C++ preprocessor written like this:

  #ifdef cpp_variable
   //x+y;
  #endif

please anyone tell me how to define this in Makefile.

thanks!

Answer 1

This is compiler specific.

GCC uses -Dcpp_variable=VALUE or just -Dcpp_variable

Microsoft 's compilers use /D

Answer 2

Search your compiler documentation to find how to do that.

For example for g++ the syntax is :

g++ -Dcpp_variable <other stuff>

Which corresponds to adding

CPPFLAGS += -Dcpp_variable

in your makefile.

Answer 3

添加到Makefile：

CPPFLAGS = -Dcpp_variable

Answer 4

语法是特定于编译器的，因为gcc使用-D选项，如下所示： -Dcpp_variable 。

Answer 5

Take a variable in Makefile and whatever you need to define in it just add -DXXX. Where XXX in you case is cpp_variable.

For example

COMPILE_OPTS = -DXXX

g++ -c $(COMPILE_OPTS) $<