Makefile macro definition: Extra_cflags + =-D with Config_ =y

Extra_cflags + =-D with Config_ =y

1.

If you define a macro config_debug

Defined in. C as: #define Config_debug

Defined in Makefile as: config_debug=y

If we want to enter a macro definition for a. c file in makefile, use Extra_cflags + = Dconfig_debug(equivalent to defining #define in. c Files config_ DEBUG)

At this point config_debug=y and extra_cflags + = Dconfig_debug The difference should you have seen, the former is used for makefile compile, for example obj-(config_ DEBUG) + = TEST.O, while the latter is used in the. C source file, for example:

#if defined (config_debug)

...

#else

...

#endif

2.

If you define a macro Config_debug = 3

Defined in. C as: #define CONFIG_DEBUG 3

If we want to enter a macro definition for the. c file in makefile, use extra_cflags + =-dconfig_debug=3

At this point the definitions are exactly the same.

Makefile macro definition: Extra_cflags + =-D with Config_ =y