Makefile shared library error - linux

Question

I was doing makefile test for creating static library and creating dynamic library from it. I have foo.h foo.c bar.c and main.c files in my directory.
I wrote a Makefile as follows:
#This makefile demonstrate the shared and static library creation.
CFLAGS = -Wall -Werror -fPIC
CFLAGS1 = -Wall
inc = /home/betatest/Public/implicit-rule-archive
all : foo.o bar.o libfoo.a libfoo.so run
foo.o: foo.c foo.h
#echo "Making the foo.o"
$(CC) -c $(CFLAGS) $< -o $#
bar.o : bar.c foo.h
#echo "Making the bar.o"
$(CC) -c $(CFLAGS) $< -o $#
libfoo.a(foo.o bar.o) : foo.o bar.o
ar cr $# $^
libfoo.so : libfoo.a
$(CC) -shared -o $# $^
run : main.c
$(CC) -L$(inc) $(CFLAGS1) -o $# $< -lfoo
.PHONY : clean
clean :
-rm -f *.o run libfoo.*
while making it gives the following the following errors:
Making the foo.o
cc -c -Wall -Werror -fPIC foo.c -o foo.o
Making the bar.o
cc -c -Wall -Werror -fPIC bar.c -o bar.o
make: *** No rule to make target 'libfoo.a', needed by 'all'. Stop.
I have written the archive statement as :
libfoo.a(foo.o bar.o) : foo.o bar.o
ar cr $# $^
from this to:
libfoo.a(*.o) : *.o
ar cr $# $^
Can I write the statement like this because in both the cases the error is the same.
I don't understand where I am going wrong. Thanks!!!!!

Answer 1

Instead of libfoo.a(foo.o bar.o) you want plain libfoo.a : foo.o bar.o.
Another thing is that .a files are normally built for linking against the final executable, hence object files for .a are compiled as position-dependent code. Shared libraries, on the other hand, require code compiled as position independent.
Hence, you can:
Get rid of libfoo.a.
Produce header dependencies automatically.
Establish complete dependencies on your targets so that make -j works robustly.
Set rpath so that run always finds libfoo.so in its directory.
This way:
CFLAGS = -Wall -Werror
LDFLAGS = -L/home/betatest/Public/implicit-rule-archive -Wl,-rpath,'$$ORIGIN'
all : run
run : main.o libfoo.so
$(CC) $(LDFLAGS) -o $# $^
libfoo.so : CFLAGS += -fPIC # Build objects for .so with -fPIC.
libfoo.so : foo.o bar.o
$(CC) -shared -o $# $^
# Compile any .o from .c. Also make dependencies automatically.
%.o : %.c
$(CC) -c $(CFLAGS) -o $# -MD -MP $<
# Include dependencies on subsequent builds.
-include $(wildcard *.d)
.PHONY : all clean
clean :
-rm -f *.o *.d run libfoo.*