CODEWITHSUNDEEP
cmakefile
Jerry
Jerry

Reputation: 323

GNU make undefined reference to functions defined in shared library

I am trying to link to a shared library. But I kept getting the undefined reference error. The following is makefile:

LIBDIR :=./lib
LIB :=-lminus 
OBJDIR :=objdir
SOURCES=$(wildcard ./src/*.c)
OBJS :=$(patsubst ./src/%.c, $(OBJDIR)/%.o, $(SOURCES))

INCPATH = -Ilib -Isrc
vpath %.h ./src ./lib
vpath %.c ./src ./lib
optest : $(OBJS)
    cc -o optest $(OBJS)

$(OBJDIR)/main.o : main.c add.h mul.h did.h minus.h 
    cc $(INCPATH) -o $@ -c $< -L$(LIBDIR) $(LIB) 

$(OBJDIR)/%.o: %.c %.h | $(OBJDIR)
    cc -o $@ -c $<

$(OBJDIR):
    mkdir $@


clean :
    rm -rf $(OBJDIR)
    rm -f optest
    rm -f ./src/*.o

The shared library is called libminus, which is put in the ./lib directory. The main function in main.c uses the function minus defined in this library. I searched online, people met this problem before. Most of their problems were solved after the shared libraries were put after the object files in the rule command. I also tried this, but it didn't work for me. The error I got is as follows:

mkdir objdir
cc -o objdir/mul.o -c ./src/mul.c
cc -o objdir/did.o -c ./src/did.c
cc -Ilib -Isrc -o objdir/main.o -c ./src/main.c -L./lib -lminus  
cc -o objdir/add.o -c ./src/add.c
cc -o optest  objdir/mul.o  objdir/did.o  objdir/main.o  objdir/add.o
objdir/main.o: In function `main':
main.c:(.text+0xa5): undefined reference to `minus'
collect2: error: ld returned 1 exit status
makefile:11: recipe for target 'optest' failed
make: *** [optest] Error 1

Can any one give some suggestion? Thank you.

Upvotes: 0

Views: 453

Answers (1)

Kaz
Kaz

Reputation: 58647

You're putting the lib stuff into the wrong rule:

$(OBJDIR)/main.o : main.c add.h mul.h did.h minus.h 
    cc $(INCPATH) -o $@ -c $< -L$(LIBDIR) $(LIB)

This just compiles main.c to main.o. The -L and $(LIB) don't belong here. They have to be in the build recipe of this rule, which links the executable:

optest : $(OBJS)
    cc -o optest $(OBJS)

Upvotes: 2

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