Gnu Makefile的多行变量展开问题

[torthtyo]

最近在玩Openjdk9，其中有些makefile的宏（多行变量）看不懂，不知到makefile的问题哪里发帖比较好，暂时发到这里，希望熟悉makefile的人能够多多指教。

Openjdk9 forest url：http://hg.openjdk.java.net/jdk9/jdk9

在root repo 下面的：make/Main。gmk 有一段代码调用eval展开多行变量：

################################################################################
# Targets for compiling native executables
$(eval $(call DeclareRecipesForPhase, LAUNCHER, \
    TARGET_SUFFIX := launchers, \
    FILE_PREFIX := Launcher, \
    MAKE_SUBDIR := launcher, \
    CHECK_MODULES := $(ALL_MODULES), \
    USE_WRAPPER := true))

ALL_TARGETS += $(LAUNCHER_TARGETS)

################################################################################

多行变量的定义在：make/MakeHelpers.gmk

# Helper macro for DeclareRecipesForPhase
# Declare a recipe for calling the module and phase specific makefile.
# If there are multiple makefiles to call, create a rule for each topdir
# that contains a makefile with the target $module-$suffix-$repodir, 
# (i.e: java.base-gensrc-jdk)
# Normally there is only one makefile, and the target will just be
# $module-$suffix
# Param 1: Name of list to add targets to
# Param 2: Module name
# Param 3: Topdir
define DeclareRecipeForModuleMakefile
  ifeq ($$($1_MULTIPLE_MAKEFILES), true)
    $2-$$($1_TARGET_SUFFIX): $2-$$($1_TARGET_SUFFIX)-$$(notdir $3)
    $1 += $2-$$($1_TARGET_SUFFIX)-$$(notdir $3)

    $2-$$($1_TARGET_SUFFIX)-$$(notdir $3):
  else
    $2-$$($1_TARGET_SUFFIX):
  endif
    $(ECHO) $(LOG_INFO) "Building $$@"
        ifeq ($$($1_USE_WRAPPER), true)
      +($(CD) $(SRC_ROOT)/make && $(MAKE) $(MAKE_ARGS) \
          -f ModuleWrapper.gmk \
              $$(addprefix -I, $$(wildcard $$(addprefix $3/, $(MAKE_MAKEDIR_LIST)) \
              $$(addsuffix /$$($1_MAKE_SUBDIR), $$(addprefix $3/, $(MAKE_MAKEDIR_LIST))))) \
              MODULE=$2 MAKEFILE_PREFIX=$$($1_FILE_PREFIX))
        else
      +($(CD) $$(dir $$(firstword $$(wildcard $$(patsubst %, \
              $3/%/$$($1_MAKE_SUBDIR)/$$($1_FILE_PREFIX)-$2.gmk, $(MAKE_MAKEDIR_LIST))))) \
        && $(MAKE) $(MAKE_ARGS) \
              -f $$($1_FILE_PREFIX)-$2.gmk \
              $$(addprefix -I, $$(wildcard $$(addprefix $3/, $(MAKE_MAKEDIR_LIST)) \
              $$(addsuffix /$3, $$(addprefix $3/, $(MAKE_MAKEDIR_LIST))))) \
              MODULE=$2)
        endif

endef

# Helper macro for DeclareRecipesForPhase
# Param 1: Name of list to add targets to
# Param 2: Module name
define DeclareRecipesForPhaseAndModule
  $1_$2_TOPDIRS := $$(strip $$(sort $$(foreach d, $(MAKE_TOPDIR_LIST), \
      $$(patsubst $$d/%, $$d, $$(filter $$d/%, \
          $$(wildcard $$(patsubst %, %/$$($1_MAKE_SUBDIR)/$$($1_FILE_PREFIX)-$2.gmk, \
          $$(foreach s, $(MAKE_MAKEDIR_LIST), \
              $$(addsuffix /$$s, $(MAKE_TOPDIR_LIST))))))))))

  # Only declare recipes if there are makefiles to call
  ifneq ($$($1_$2_TOPDIRS), )
    $$(foreach d, $$($1_$2_TOPDIRS), \
        $$(eval $$(call DeclareRecipeForModuleMakefile,$1,$2,$$d)))
    $1 += $2-$$($1_TARGET_SUFFIX)
    $1_MODULES += $2
  endif
endef

# Declare recipes for a specific module and build phase if there are makefiles
# present for the specific combination.
# Param 1: Name of list to add targets to
# Named params:
# TARGET_SUFFIX : Suffix of target to create for recipe
# MAKE_SUBDIR : Subdir for this build phase
# FILE_PREFIX : File prefix for this build phase
# USE_WRAPPER : Set to true to use ModuleWrapper.gmk
# CHECK_MODULES : List of modules to try
# MULTIPLE_MAKEFILES : Set to true to handle makefils for the same module in
#                      phase in multiple repos
# Exported variables:
# $1_MODULES : All modules that had rules generated
# $1_TARGETS : All targets generated
define DeclareRecipesForPhase
  $(foreach i,2 3 4 5 6 7, $(if $($i),$(strip $1)_$(strip $($i)))$(NEWLINE))
  $(if $(8),$(error Internal makefile error: Too many arguments to \
      DeclareRecipesForPhase, please update MakeHelper.gmk))

  $$(foreach m, $$($(strip $1)_CHECK_MODULES), \
      $$(eval $$(call DeclareRecipesForPhaseAndModule,$(strip $1),$$m)))

  $(strip $1)_TARGETS := $$($(strip $1))
endef

################################################################################

里面$(foreach i,2 3 4 5 6 7, $(if $($i),$(strip $1)_$(strip $($i)))$(NEWLINE))这句就没看懂。后面貌似很多变量有用到，比如 $$(foreach m, $$($(strip $1)_CHECK_MODULES) 前面 $(strip $1)_$(strip $($i)))$(NEWLINE) 定义的变量在后面用到了，但是我理解前面只是打印出$(strip $1)_$(strip $($i)))$(NEWLINE) 并没有赋值，这样算定义了一个变量吗？

我看到后面很多代码引用到了第一个foreach 定义的变量，如：$$($(strip $1)_CHECK_MODULES)， $$($1_MAKE_SUBDIR)/$$($1_FILE_PREFIX)。有没有熟悉named param的解释一下？

[mLee79]

$(foreach i,2 3 4 5 6 7, $(if $($i),$(strip $1)_$(strip $($i)))$(NEWLINE)) ------------------------------------------------------------------------------------------- $(eval LAUNCHER_TARGET_SUFFIX := launchers LAUNCHER_FILE_PREFIX := Launcher ..... LAUNCHER_USE_WRAPPER := true ) 其他自己带进去跟. 在 Makefile 里多用 $(info .... ) $(error ....) 打 trace, 看不懂的地方就加个 $(error ..... ) 上去看看展开是什么..

[mLee79]

$(foreach i,2 3 4 5 6 7, $(if $($i),$(strip $1)_$(strip $($i)))$(NEWLINE)) ------------------------------------------------------------------------------------------- $(eval LAUNCHER_TARGET_SUFFIX := launchers LAUNCHER_FILE_PREFIX := Launcher ..... LAUNCHER_USE_WRAPPER := true ) 其他自己带进去跟. 在 Makefile 里多用 $(info .... ) $(error ....) 打 trace, 看不懂的地方就加个 $(error ..... ) 上去看看展开是什么..

[赵4老师]

搜“跟我一起写makefile”