这些对象文件是如何在Makefile中编译的?

时间:2017-06-21 04:48:39

标签: makefile

我不知道是否有任何隐式编译目标文件的方法。这是“学习艰难的道路”一书中的Makefile。

CFLAGS=-g -O2 -Wall -Wextra -Isrc -rdynamic -DNDEBUG $(OPTFLAGS)
LIBS=-ldl $(OPTLIBS)
PREFIX?=/usr/local

SOURCES=$(wildcard src/**/*.c src/*.c)
OBJECTS=$(patsubst %.c,%.o,$(SOURCES))

TEST_SRC=$(wildcard tests/*_tests.c)
TESTS=$(patsubst %.c,%,$(TEST_SRC))

TARGET=build/liblcthw.a
SO_TARGET=$(patsubst %.a,%.so,$(TARGET))

# The Target Build
all: $(TARGET) $(SO_TARGET) tests

dev: CFLAGS=-g -Wall -Isrc -Wall -Wextra $(OPTFLAGS)
dev: all

$(TARGET): CFLAGS += -fPIC

$(TARGET): build $(OBJECTS)
    ar rcs $@ $(OBJECTS)
    ranlib $@
$(SO_TARGET): $(TARGET) $(OBJECTS)
    $(CC) -shared -o $@ $(OBJECTS)

build:
    @mkdir -p build
    @mkdir -p bin

# The Unit Tests
.PHONY: tests
tests: CFLAGS += $(TARGET)
tests: $(TESTS)
    sh ./tests/runtests.sh

# The Cleaner
clean:
    rm -rf build $(OBJECTS) $(TESTS)
    rm -f tests/tests.log
    find . -name "*.gc*" -exec rm {} \;
    rm -rf `find . -name "*.dSYM" -print`

# The Install
install: all
    install -d $(DESTDIR)/$(PREFIX)/lib/
    install $(TARGET) $(DESTDIR)/$(PREFIX)/lib/

# The Checker
check:
    @echo Files with potentially dangerous functions.
    @egrep '[^_.>a-zA-Z0-9](str(n?cpy|n?cat|xfrm|?dup|str|pbrk|tok|_)\
        |stpn?cpy|a?sn?printf|byte_)' $(SOURCES) || true

我没有看到任何将.c文件编译为.o文件的行。但是当我运行make时,结果就是:

cc -g -O2 -Wall -Wextra -Isrc -rdynamic -DNDEBUG -fPIC -c -o src/lcthw/list.o src/lcthw/list.c
ar rcs build/liblcthw.a src/lcthw/list.o
ranlib build/liblcthw.a

任何人都可以解释一下吗?

1 个答案:

答案 0 :(得分:0)

Make知道如何将.c文件编译到相应的.o文件中 - 它是一个内置规则。与语言类似。它还知道如何从单个源文件构建程序。等

您可以使用make -p -f /dev/null查看make定义的所有内置规则和默认宏。我从GNU Make 3.81获得的部分输出是:

…
LINK.c = $(CC) $(CFLAGS) $(CPPFLAGS) $(LDFLAGS) $(TARGET_ARCH)
…
COMPILE.c = $(CC) $(CFLAGS) $(CPPFLAGS) $(TARGET_ARCH) -c
…
%: %.c
#  commands to execute (built-in):
    $(LINK.c) $^ $(LOADLIBES) $(LDLIBS) -o $@
…
%.o: %.c
#  commands to execute (built-in):
    $(COMPILE.c) $(OUTPUT_OPTION) $<
…