make命令回显Makefile执行脚本命令

时间：2023-03-08 17:44:38
make命令回显Makefile执行脚本命令 
/**********************************************************************

 *                make命令回显Makefile执行脚本命令

 * 说明：

 *     当我们拿到别人的源代码的时候，如果是用Makefile组织的，同时希望能够

 * 跟踪一下源代码的编译架构，从而建立对源代码的组织架构的全局理解，可以通

 * 过传入V=1打开执行回显功能，当然要源代码的Makefile支持这个功能。

 *

 *                                2018-6-29 深圳 宝安西乡 曾剑锋

 *********************************************************************/

一、参考文档：

    https://github.com/ZengjfOS/Buildroot/blob/fsl_uboot_L4.1.15_from_TP/Makefile

二、Makefile Help

    # Beautify output

    # ---------------------------------------------------------------------------

    #

    # Normally, we echo the whole command before executing it. By making

    # that echo $($(quiet)$(cmd)), we now have the possibility to set

    # $(quiet) to choose other forms of output instead, e.g.

    #

    #         quiet_cmd_cc_o_c = Compiling $(RELDIR)/$@

    #         cmd_cc_o_c       = $(CC) $(c_flags) -c -o $@ $<

    #

    # If $(quiet) is empty, the whole command will be printed.

    # If it is set to "quiet_", only the short version will be printed.

    # If it is set to "silent_", nothing will be printed at all, since

    # the variable $(silent_cmd_cc_o_c) doesn't exist.

    #

    # A simple variant is to prefix commands with $(Q) - that's useful

    # for commands that shall be hidden in non-verbose mode.

    #

    #    $(Q)ln $@ :<

    #

    # If KBUILD_VERBOSE equals  then the above command will be hidden.

    # If KBUILD_VERBOSE equals  then the above command is displayed.

    #

    # To put more focus on warnings, be less verbose as default

    # Use 'make V=1' to see the full commands

    ifeq ("$(origin V)", "command line")

      KBUILD_VERBOSE = $(V)

    endif

    ifndef KBUILD_VERBOSE

      KBUILD_VERBOSE =

    endif

    ifeq ($(KBUILD_VERBOSE),)

      quiet =

      Q =

    else

      quiet=quiet_

      Q = @

    endif

三、命令解析

    . %config：

        [...省略]

        %config: scripts_basic outputmakefile FORCE

            $(Q)$(MAKE) $(build)=scripts/kconfig $@

        [...省略]

    . 添加调试信息：

        [...省略]

        %config: scripts_basic outputmakefile FORCE

            $(info zengjf $@ $(Q))

            $(Q)$(MAKE) $(build)=scripts/kconfig $@

        [...省略]

    . $(info zengjf $@ $(Q))输出信息：

        zengjf mx6dlsabresd_defconfig @

    . 可知：$(Q) = @

    . 从上面Makefile Help中可以，Makefile中的Q变量和KBUILD_VERBOSE有关，KBUILD_VERBOSE和make执行的时候V变量有关；

    . 所以执行make相关的命令，加入V=1就可以回显make命令执行的流程了。

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