makefile - Makefile总是重建

Question

我正在使用以下简单的Makefile来构建一些简单的文件。我真的是制作Makefile的新手。我不知道为什么它会继续重建，即使文件是在首次制作之后就构建的，而且我也没有编辑任何文件。

EXE    = nextgenrsm
CC     = gcc
LIBS   = StarterWare_Files/
CFLAGS = -c 

INCLUDE_PATH =  StarterWare_Files/

MAIN_SRC = $(wildcard *.c)
MAIN_OBS = $(patsubst %.c,%.o,$(MAIN_SRC))

LIB_SRC = $(wildcard StarterWare_Files/*.c)
LIB_OBS = $(patsubst StarterWare_Files/%.c,%.o,$(LIB_SRC))

output: $(EXE)

$(EXE): $(MAIN_OBS) $(LIB_OBS)
    $(CC) $(MAIN_OBS) $(LIBS)$(LIB_OBS) -o $(EXE) 

$(MAIN_OBS): $(MAIN_SRC) 
    $(CC) $(CFLAGS) *.c -I$(INCLUDE_PATH)

$(LIB_OBS): $(LIB_SRC) 
    cd $(LIBS); \
    $(CC) $(CFLAGS) *.c -I../

clean:
    rm -rf $(LIBS)*.o $(EXE) *.o

新编辑的制作文件

EXE    = nextgenrsm
CC     = gcc
LIBS   = StarterWare_Files/
CPPFLAGS = _IStarterWare_Files/


MAIN_OBS = $(patsubst %.c,%.o,$(wildcard *.c))
LIB_OBS  = $(patsubst %.c,%.o,$(wildcard StarterWare_Files/*.c))

all: $(EXE)

$(EXE): $(MAIN_OBS) $(LIB_OBS)
   $(CC) -o $@ $(LDFLAGS) $(MAIN_OBS) $(LIB_OBS) $(LDLIBS)

%.o: %.c 
   $(CC) -o $@ -MD -MP $(CPPFLAGS) $(CFLAGS) -c $^

ALL_DEPS = $(patsubst %.o,%.d,$(MAIN_OBS), $(LIB_OBS))
-include $(ALL_DEPS)

clean:
   rm -f $(LIB_OBS) $(EXE) $(MAIN_OBS) $(ALL_DEPS)

.PHONY: all clean

每当我触摸StarterWare_Files/example.h并尝试再次进行制作时，都会引发错误，gcc无法将-o与-c或-S与多个文件一起指定。基本上，该命令将变为以下形式:gcc -o main.o -IStarterWare_Files -c main.c StarterWare_Files/test.h StarterWare_Files/add.h。

Answer 1

您的默认目标是output，但是您的makefile永远不会生成这样的文件，因此，每次您调用make时，它都会尝试生成output文件。

解决方案是将output目标标记为phony target。以及clean目标:

.PHONY: output clean

您可以利用built-in rules来从.o和automatic variables编译.c，以将您的makefile减少为:

EXE    := nextgenrsm
CC     := gcc
LIBS   := StarterWare_Files/
CPPFLAGS := -IStarterWare_Files

MAIN_OBS := $(patsubst %.c,%.o,$(wildcard *.c))
LIB_OBS  := $(patsubst %.c,%.o,$(wildcard StarterWare_Files/*.c))

all: $(EXE)
$(EXE) : $(MAIN_OBS) $(LIB_OBS)
    $(CC) -o $@ $(LDFLAGS) $^ $(LDLIBS)

clean:
    rm -f $(MAIN_OBS) $(LIB_OBS) $(EXE)

.PHONY: all clean   

如果您想自动生成 header 依赖项，请添加:

# This rule produces .o and also .d (-MD -MP) from .c.
%.o : %.c
    $(CC) -o $@ -MD -MP $(CPPFLAGS) $(CFLAGS) -c $<

# This includes all .d files produced along when building .o.
# On the first build there are not going to be any .d files.
# Hence, ignore include errors with -.
ALL_DEPS := $(patsubst %.o,%.d,$(MAIN_OBS) $(LIB_OBS))
-include $(ALL_DEPS)

clean:
    rm -f $(MAIN_OBS) $(LIB_OBS) $(EXE) $(ALL_DEPS)