make 笔记

GNU make

文档整理说明

• 本文档是旧版零散 make 记录收敛后的主文档.
• 后续统一以当前路径为准, 不再保留根路径兼容页.

查看所有 targets

.PHONY: no_targets__ list
no_targets__:
list:
	sh -c "$(MAKE) -p no_targets__ | awk -F':' '/^[a-zA-Z0-9][^\$$#\/\t=]*:([^=]|$$)/ {split(\$$1,A,/ /);for(i in A)print A[i]}' | grep -v '__\$$' | sort"

变量

赋值
    x = yes
    x ?= yes, 如果 x 未定义则赋值, 否则不处理
    x := $(y) yes, 只使用前面已经确定的变量值
    x += yes, 追加新的值

延迟展开与立即展开
    x = $(y) yes, y 的值会根据后续定义继续变化
    x := $(y) yes, y 的值在当前行就确定

打印变量
    $(warning $(XXX))
    $(error $(XXX))

判断

ifeq ($(VALIDATION),1)
ifdef PLATFORM
$(error PLATFORM: $(PLATFORM) defined)
else
$(error PLATFORM: $(PLATFORM) undefined)
endif
endif

Makefile 规则

Targets: Prerequisites [;Command]
    Command

Command 必须以 [Tab] 开始.

当规则的 target 是一个文件时, 它的任何一个依赖文件被修改后, 在执行 `make <target>` 时这个目标文件都会被重新生成.

普通依赖与 order-only 依赖

target : normal-prerequisites | order-only-prerequisites

• normal-prerequisites 是普通依赖.
• order-only-prerequisites 只保证执行顺序, 不会因为其变化而触发目标重新生成.

示例:

test: | $(OUTPUT_DIR)

伪目标

.PHONY : clean

clean :
    [-]rm *.o *.bin *.lst a.out

自动变量

foo.o : foo.c
    cc -c $(CFLAGS) $^ -o $@

• $@, 目标文件
• $^, 所有依赖文件
• $<, 第一个依赖文件

常用函数

过滤与替换

$(filter-out a.cpp, $(SRC)), 从 SRC 中排除 a.cpp

patsubst: 模式替换
obj = $(patsubst %.c, %.o, $(names))

subst: 普通字符串替换

foreach

$(foreach <var>,<list>,<text>), 循环

names := a b c d
files := $(foreach n,$(names),$(n).o)
得到 files 为 "a.o b.o c.o d.o"

wildcard / notdir / dir

wildcard: 扩展通配符
sources = $(wildcard *.c ./sub/*.c)

notdir: 去除路径
names = $(notdir $(sources))

dir: 只保留路径

call

call 函数是唯一一个可以创建定制化参数函数的引用函数

MAKECMDGOALS

"MAKECMDGOALS" 记录了命令行参数指定的终极目标列表

模式替换示例

foo := a.o b.o l.a c.o
bar := $(foo:%.o=%.c)

sets 'bar' to 'a.c b.c l.a c.c'

utils

# Function to traverse directory tree and find all files matching pattern from list
# Usage: $(call search_tree,src/,*.c *.cpp)
search_tree = $(sort $(if $1,$(foreach d,$(wildcard $1/*),$(call $0,$d,$2)$(filter $(subst *,%,$2),$d))))

# recursive wildcard
rwildcard = $(foreach d,$(wildcard $1*),$(call rwildcard,$d/,$2) $(filter $(subst *,%,$2),$d))

# Same as above, but removes directory prefix
search_dir = $(patsubst $1/%,%,$(call search_tree,$1,$2))

# Generates subdirectories recursively
# Usage $(call subdirs,path)
subdirs = $(filter-out .,$1 $(if $(filter-out .,$(call dirx,$1)),$(call $0,$(call dirx,$1))))

# Directory part of path but with trailing slash removed
dirx = $(sort $(patsubst %/,%,$(dir $1)))

# Changes \ to /, removes '/./' and trailing /.
normalize_path = $(patsubst %/.,%,$(subst /./,/,$(subst \,/,$1)))

# Converts relative path to absolute path
# Usage: $(call resolve_path,root,path_list)
resolve_path = $(call normalize_path,$(foreach p,$2,$(if $(call is_abs,$p),$p,$(addprefix $1/,$p))))

# Generates a build rule for a list of targets (T represent a target within a rule)
# Usage: $(call generate_rules,build_rule_name,targets)
generate_rules = $(foreach T,$2,$(eval $(value $1)))

# Escape given list of characters in text with escape character
# Usage: $(call esc,characters,escape_with,text)
esc = $(if $(firstword $1),$(subst $(firstword $1),$2$(firstword $1),$(call $0,$(wordlist 2, 100,$1),$2,$3)),$3)

# Modifies system PATH by prepending provided arguments. No spaces are allowed
# Usage $(call make_PATH,path1 path2)
make_PATH = $(eval export PATH = $(subst $(space),,$(foreach p,$1,$(call sys_path,$p)$(PATH_SEP)))$(PATH))

# Convert path to section name prefix: change / to . and remove src.
dir_to_sect = .$(subst src.,,$(subst /,.,$(basename $(1))))