Question

我正在尝试在Trivia服务器程序中使用mongo C驱动程序，用它来跟踪登录信息分数等。

我花了相当多的时间来弄清楚如何在makefile中编译东西但是我能够包含mongoc.h所以像mongoc_client这样的东西工作得很好。一旦我尝试实际使用一个函数，例如mongoc_init我得到

> undefined reference to `mongoc_init'

我觉得事情应该链接，因为mongoc.h包含所有其他头文件，看起来它正确链接。这是我的makefile - 我不知道该怎么做，甚至不知道提供什么信息来解决这个问题。

client:
    make -f makefile.client

server:
    make -f makefile.server

clean:
    rm -f *~ *.o tserve core tclient core *.tar *.zip *.gzip *.bzip *.gz

^ Makefile

C = gcc
CFLAGS = -g -Wall
LDFLAGS = -lpthread
INFO = -L/usr/local/lib -I/usr/local/include/libmongoc-1.0 -I/usr/local/include/libbson-1.0 -lmongoc-1.0 -lbson-1.0

all: tserve

csapp.o: csapp.c csapp.h
        $(CC) $(CFLAGS) -c csapp.c

tserve.o: tserve.c readq.h csapp.h
        $(CC) $(CFLAGS) -c tserve.c $(INFO)

readq.o: readq.c readq.h csapp.h
        $(CC) $(CFLAGS) -c readq.c

tserve: tserve.o readq.o csapp.o

^ makefile.server

C = gcc
CFLAGS = -g -Wall
LDFLAGS = -lpthread

all: tclient

csapp.o: csapp.c csapp.h
        $(CC) $(CFLAGS) -c csapp.c

tclient.o: tclient.c csapp.h
        $(CC) $(CFLAGS) -c tclient.c

tclient: tclient.o csapp.o

^ makefile.client

如果值得注意 - 系统问题是使用以下代码安装了驱动程序

system("wget https://github.com/mongodb/mongo-c-driver/releases/download/1.0.2/mongo-c-driver-1.0.2.tar.gz");
system("tar -xzf mongo-c-driver-1.0.2.tar.gz");
system("rm mongo-c-driver-1.0.2.tar.gz");
if (chdir("mongo-c-driver-1.0.2"))
    perror("error:");
system("./configure --prefix=/usr --libdir=/usr/lib64");
system("make");
system("sudo make install");

代码也在https://www.github.com/decix/TriviaServer

Answer 1

您只能使用包含INFO的{{1}}变量（这是您需要的）来构建-lmongoc-1.0 -lbson-1.0。在此构建步骤中，不涉及链接器，因此不评估tserve.o选项并且不执行任何操作。相反，您需要在构建-l时指定它们。

您可以通过提供执行此操作的tserve的配方来解决此问题，例如

tserve

...但在我看来，将tserve: tserve.o readq.o csapp.o $(CC) $(LDFLAGS) $(INFO) -o $@ $+拆分并将部分放入预定义规则用于相关目的的变量会更好。然后你的整个Makefile可以替换为

INFO

然后将通过隐式规则构建# C compiler CC = gcc # C compiler flags CFLAGS = -g -Wall # C preprocessor flags CPPFLAGS = -I/usr/local/include/libmongoc-1.0 -I/usr/local/include/libbson-1.0 -pthread # Linker flags LDFLAGS = -L/usr/local/lib -pthread # Libraries LDLIBS = -lmongoc-1.0 -lbson-1.0 all: tserve csapp.o: csapp.c csapp.h tserve.o: tserve.c readq.h csapp.h readq.o: readq.c readq.h csapp.h tserve: tserve.o readq.o csapp.o文件，这些规则从相应的.o文件生成它们并使用.c和CPPFLAGS，从而省去了指定配方的麻烦显式 - 仅存在跟踪依赖关系的规则 - 链接步骤使用使用CFLAGS和LDFLAGS的隐式规则。请注意，我在LDLIBS和-pthread中都提供了CPPFLAGS，因为它与预处理器和链接器都相关。

有关详细信息，请参阅GNU制作手册中有关implicit rules的内容，并谈到依赖关系跟踪，您可能会发现this article关于自动化它的启发。

Answer 2

the following file is expected to be named Makefile.mak


# note: with very minor changes this should work for most C projects
#       irregardless of the OS being used

SHELL := /bin/sh

.PHONY: all clean

#
# macro for all *.c files
# (NOTE:
# (the following 'wildcard' will pick up ALL .c files
# (like FileHeader.c and FunctionHeader.c
# (which should not be part of the build
# (so be sure no unwanted .c files in directory
# (or change the extension
#
SRC := $(wildcard *.c)
OBJ := $(SRC:.c=.o)
DEP := $(SRC:.c=.d)
INC := $(SRC:.c=.h)


CC       := /usr/bin/gcc
MAKE     := /usr/bin/make


name := tserve

CFLAGS := -c -g -std=c11 -Wall -Wextra -pedantic-errors
#CPPFLAGS += =MD

# when #(DEBUG) is used in the compile/link steps,
# them max info for the gdb debugger is generated
DEBUG   := -ggdb3
LDFLAGS := -L/lib -L/usr/lib -L/usr/local/lib

LIBS :=  -lpthread -lmongoc-1.0 -lbson-1.0

INC := -I/usr/local/include/libmongoc-1.0 -I/usr/local/include/libbson-1.0
name := tserve

all: $(name)


#
# link the .o files into the executable
# using the linker flags
# -- explicit rule
#
$(name): $(OBJ)
    #
    # ======= $(name) Link Start =========
    $(CC) $(LDFLAGS) -o $@ $(OBJ) $(LIBS)
    # ======= $(name) Link Done ==========
    #

#
#create dependancy files
# -- inference rule
#
%.d: %.c Makefile.mak
    #
    # ========= START $< TO $@ =========
    $(CC) -M $(CPPFLAGS) $< > $@.$$$$;                      \
    sed 's,\($*\)\.o[ :]*,\1.o $@ : ,g' < $@.$$$$ > $@;     \
    rm -f $@.$$$$
    # ========= END $< TO $@ =========

#
# compile the .c file into .o files using the compiler flags
# -- inference rule
#
%.o: %.c %.d
    #
    # ========= START $< TO $@ =========
    $(CC) $(CCFLAGS) -c $< -o $@ -I. $(INC)
    # ========= END $< TO $@ =========
    #


clean:
    # ========== CLEANING UP ==========
    rm -f *.o
    rm -f $(name).map
    rm -f $(name)
    rm -f *.d
    # ========== DONE ==========


ifneq "$(MAKECMDGOALS)" "clean"
-include $(DEP)
endif

mongoc_init undefined reference

2 个答案: