Getting undefined reference error from makefile

Question

I am working on a project that uses some code written by someone else inside a folder called CommandParser. My project is called TCP_IP and inside it there is the CommandParser folder.

This is my makefile.

TARGET = $(BIN_DIR)/sim_tcp_ip
LIBS = -lpthread -L ./CommandParser -lcli
OBJS = $(OBJ_DIR)/prueba.o \
       $(OBJ_DIR)/ListaEnlazada.o \
       $(OBJ_DIR)/Grafico.o \
       $(OBJ_DIR)/Net.o \
       $(OBJ_DIR)/Topologias.o
BIN_DIR = ./bin
OBJ_DIR = ./obj
INC_DIR = ./inc
SRC_DIR = ./src
CFLAGS = -Wall -I$(INC_DIR)

$(TARGET): $(OBJS) CommandParser/libcli.a
    mkdir -p $(BIN_DIR)
    gcc $(CFLAGS) $(OBJS) -o $(TARGET) $(LIBS)
    
$(OBJ_DIR)/%.o : %.c
    mkdir -p $(OBJ_DIR)
    gcc -c -MD $(CFLAGS) $< -o $@
    
CommandParser/libcli.a:
    (cd CommandParser; make)

-include $(OBJ_DIR)/*.d
    
.PHONY: clean
clean:
    rm -rf $(OBJ_DIR) $(BIN_DIR)
    (cd CommandParser; make clean)
all:
    make
    (cd CommandParser; make)

CommandParser has its own makefile.

CC=gcc
CFLAGS=-g -Wall
INCLUDES=-I .
CLILIB=libcli.a
TARGET:exe ${CLILIB}
OBJ=cmd_hier.o parser.o serialize.o string_util.o clistd.o clicbext.o gluethread/glthread.o ut/utinfra/ut_parser.o
exe:testapp.o ${CLILIB}
    @echo "Building final executable"
    @ ${CC} ${CFLAGS} ${INCLUDES} testapp.o -o exe -L . -lcli -lpthread -lrt
cmd_hier.o:cmd_hier.c
    @echo "Building cmd_hier.o"
    @ ${CC} ${CFLAGS} -c ${INCLUDES} cmd_hier.c -o cmd_hier.o
parser.o:parser.c
    @echo "Building parser.o"
    @ ${CC} ${CFLAGS} -c ${INCLUDES} parser.c -o parser.o
gluethread/glthread.o:gluethread/glthread.c
    @echo "Building gluethread/glthread.o"
    @ ${CC} ${CFLAGS} -c ${INCLUDES} gluethread/glthread.c -o gluethread/glthread.o
serialize.o:serialize.c
    @echo "Building serialize.o"
    @ ${CC} ${CFLAGS} -c ${INCLUDES} serialize.c -o serialize.o
string_util.o:string_util.c
    @echo "Building string_util.o"
    @ ${CC} ${CFLAGS} -c ${INCLUDES} string_util.c -o string_util.o
clistd.o:clistd.c
    @echo "Building clistd.o"
    @ ${CC} ${CFLAGS} -c ${INCLUDES} clistd.c -o clistd.o
clicbext.o:clicbext.c
    @echo "Building clicbext.o"
    @ ${CC} ${CFLAGS} -c ${INCLUDES} clicbext.c -o clicbext.o
testapp.o:testapp.c
    @echo "Building testapp.o"
    @ ${CC} ${CFLAGS} -c ${INCLUDES} testapp.c -o testapp.o
ut/utinfra/ut_parser.o:ut/utinfra/ut_parser.c
    @echo "Building ut/utinfra/ut_parser.o"
    @ ${CC} ${CFLAGS} -c ${INCLUDES} ut/utinfra/ut_parser.c -o ut/utinfra/ut_parser.o
${CLILIB}: ${OBJ}
    @echo "Building Library ${CLILIB}"
    ar rs ${CLILIB} ${OBJ}
clean:
    rm -f exe
    rm -f *.o
    rm -f gluethread/*.o
    rm -f ut/utinfra/*.o
    rm -f ${CLILIB}
    rm -f CMD_HIST_RECORD_FILE.txt
install:
    cp ${CLILIB} /usr/local/lib/
    cp libcli.h /usr/include/
    cp cmdtlv.h /usr/include/
uninstall:
    rm -f /usr/local/lib/${CLILIB}
    rm -f /usr/include/libcli.h
    rm -f /usr/include/cmdtlv.h

When do make inside CommandParser, I don't get any error. However, something seems to be wrong with my makefile because if I do make in my TCP_IP folder, I get some undefined reference errors.

/usr/bin/ld: ./CommandParser/libcli.a(ut_parser.o): en la función ut_parser_init': /home/darinel/Documentos/Cursos/C++/TCP_IP/CommandParser/ut/utinfra/ut_parser.c:52: referencia a mq_open' sin definir

/usr/bin/ld: ./CommandParser/libcli.a(ut_parser.o): en la función run_test_case': /home/darinel/Documentos/Cursos/C++/TCP_IP/CommandParser/ut/utinfra/ut_parser.c:261: referencia a mq_timedreceive' sin definir

/usr/bin/ld: ./CommandParser/libcli.a(ut_parser.o): en la función cli_out': /home/darinel/Documentos/Cursos/C++/TCP_IP/CommandParser/ut/utinfra/ut_parser.c:517: referencia a mq_send' sin definir

collect2: error: ld returned 1 exit status

make: [makefile:16: bin/sim_tcp_ip] Error 1

The message shows that these errors come from the CommandParser code, and not from my code, even though it previously worked fine in the CommandParser folder.

Please don't paste images to StackOverflow; instead cut and paste the text into your question with proper formatting. Images are not searchable, we cannot cut/paste content into answers, and they aren't easy to read for some people. Thanks! — MadScientist, Sep 06 '21 at 01:03

score 3 · Accepted Answer · answered Sep 06 '21 at 02:36

It appears that the CommandParser library is looking for another library, that contains functions like mq_open, mq_send, and mq_timedreceive. If you look up these functions you'll see that they're provided by the realtime library, librt. So, you need to add the -lrt option to your link line.

Also, please pay close attention to the order of libraries on the link line. You should always order them highest-level to lowest-level. You have:

LIBS = -lpthread -L ./CommandParser -lcli

but -lpthread is a lower-level library so it should come after -lcli. Also, the modern way of building executables using threads is to use the -pthread option on BOTH the compile line AND the link line, so you should use:

LIBS = -pthread -L ./CommandParser -lcli -lrt

CFLAGS = -pthread -Wall -I$(INC_DIR)

Getting undefined reference error from makefile

1 Answers1