CODEWITHSUNDEEP
cmakefileshared-libraries
Elfayer
Elfayer

Reputation: 4571

make: *** No rule to make target `gcc', needed by `libmy.so'. Stop

I would like to compile .c files to a .so (shared library). And I don't understand why, I have that makefile that makes me an error:

LIB = libmy.so

SRC =   lib.c

CC = gcc

OBJ = $(CC) -c -fPIC $(SRC)

all: $(LIB)

re: fclean all

$(LIB): $(OBJ)
        $(CC) -shared -fPIC $(OBJ) -o $(LIB)

clean:
        $(RM) $(OBJ)

fclean: clean
        $(RM) $(LIB)

Thanks in advance for helping.

Upvotes: 0

Views: 3864

Answers (3)

Elfayer
Elfayer

Reputation: 4571

That works :

LIB = libmy.so

SRC =   lib.c

CC = gcc

OBJ = $(SRC:.c=.o)

all: $(LIB)

re: fclean all

$(LIB):
        $(CC) -c -fPIC $(SRC)
        $(CC) -shared -fPIC $(SRC) -o $(NAME)
clean:
        $(RM) $(OBJ)

fclean: clean
        $(RM) $(LIB)

I just need OBJ = $(SRC:.c=.o) in fclean

Upvotes: 0

Austin Phillips
Austin Phillips

Reputation: 15776

The problem is in the following line:

$(LIB): $(OBJ)

When expanded this becomes:

libmy.so : gcc -c -fPIC lib.c

Hence the error.

What you probably wanted was :

OBJ = lib.o

To save you having to manually convert all .c source files to .o you can use a rule like this instead of OBJ = lib.o:

OBJ = $(SRC:%.c=%.o)

This creates a variable OBJ containing a list of all the files in SRC with any .c extension changed to .o. eg. If we had SRC = foo.c bar.c then the rule above would automatically expand to:

OBJ = foo.o bar.o

Upvotes: 5

Christoph
Christoph

Reputation: 169793

$(LIB): $(OBJ)

expands to

libmy.so: gcc -c -fPIC $(SRC)

ie you put your recipe into the depency list, and make rightfully complains.

Personally, I'd write the makefile like this:

CC := gcc
RM := rm -f

LIB := libmy.so
OBJ := lib.o
GARBAGE := $(OBJ)

.PHONY: all clean realclean

all: $(LIB)

$(LIB): LDFLAGS += -shared
$(LIB): $(OBJ)
    $(CC) $(LDFLAGS) -o $@ $<

$(OBJ): CFLAGS += -fPIC
$(OBJ): %.o : %.c
    $(CC) $(CFLAGS) -c -o $@ $<

realclean: GARBAGE += $(LIB)
clean realclean:
    $(RM) $(GARBAGE)

Note that your original version did not contain a rule to make $(OBJ). If you wanted to use the implicit one, you would need to add -fPIC to CFLAGS.

Upvotes: 0

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