how to create binary and .so using libtool

Question

I have a set of cpp files that I want to compile directly into a binary and also to compile into a shared library.

I have

bin_PROGRAMS=mybin
lib_LTLIBRARIES=libmylib.la

COMMON_SOURCES=f1.cpp f2.cpp f3.cpp

mybin_SOURCES=main.cpp $(COMMON_SOURCES)
libmylib_la_SOURCES=$(COMMON_SOURCES)

When I run this the cpp files are compiled twice, once with libtool and once without and sometimes libtool/automake complains

Makefile.am: object `f1.$(OBJEXT)' created both with libtool and without`

I tried putting COMMON_SOURCES into a .a file but then libtool complains when I link a .a with a .la (saying its not portable).

What I need is something like

bin_LTPROGRAMS=mybin

but that doesnt exist

edit: clarification - I am using automake/autoconf. What I have shown above is the meat of my automake Makefile.am

Answer 1

The issue is that the common sources need to be compiled differently when they are being made into a shared object than when they are being made into a static archive; in the case of the former, for example, g++ needs to be passed the -fPIC flag.

What I suggest is using two build directories.

Assuming this source hierarchy:

./src/Makefile.am
./src/f1.cpp
./src/f2.cpp
./src/f3.cpp
./src/main.cpp
./configure.ac
./Makefile.am

you would use something like this in ./src/Makefile.am:

bin_PROGRAMS = mybin
lib_LTLIBRARIES = libmylib.la

mybin_SOURCES = main.cpp
mybin_LDADD = libmylib.la

libmylib_la_SOURCES = f1.cpp f2.cpp f3.cpp

Then you create directories Release and ReleaseDisableShared in ./. In directory ./Release you run:

../configure && make

and in ./ReleaseDisableShared you run:

../configure --disable-shared && make

After building in each build directory, you use the mybin at ./ReleaseDisableShared/src/mybin and the libmylib.so at ./Release/src/libmylib.so.

See also:

• Position-independent code
• build .o files to specific directory using automake

Answer 2

Link against the library of common sources specifically:

bin_PROGRAMS = mybin
lib_LTLIBRARIES = libmylib.la

mybin_SOURCES = main.cpp
mybin_LDADD = libmylib.la
libmylib_la_SOURCES = f1.cpp f2.cpp f3.cpp

If libmylib.la ends up using files that shouldn't be linked into mybin, create a libtool convenience library, using a Makefile.am something like this:

bin_PROGRAMS = mybin
noinst_LTLIBRARIES = libcommon.la
lib_LTLIBRARIES = libmylib.la

mybin_SOURCES = main.cpp
mybin_LDADD = libcommon.la

libmylib_la_SOURCES = f4.cpp f5.cpp f6.cpp
libmylib_la_LIBADD = libcommon.la

libcommon_la_SOURCES = f1.cpp f2.cpp f3.cpp

This will link f1.cpp, f2.cpp, f3.cpp, f4.cpp, f5.cpp and f6.cpp into libmylib.la and main.cpp, f1.cpp, f2.cpp and f3.cpp into mybin.

Answer 3

If a target contains per-target CFLAGS (or similar), automake will make separate object files for building that target. Try adding some no-op flags to mybin, something like:

mybin_CPPFLAGS = -I.

or

mybin_CPPFLAGS = -DDUMMY -UDUMMY

Answer 4

You have to give object files created with libtool a different extension so they do not conflict. In fact, those files are text files containing meta information for both object files with relocatable and non-relocatable code (this is controlled with -fPIC gcc command line argument). The real files created by libtool are usually stored in ".libs" subdirectory. The basic makefile will look like this:

CC = $(CXX)
LIBTOOL = libtool --quiet

SRC = lib.cpp test.cpp
LIB_SRC = lib.cpp $(SRC)
LIB_OBJ = $(LIB_SRC:.cpp=.lo)

EXE_SRC = exe.cpp $(SRC)
EXE_OBJ = $(EXE_SRC:.cpp=.o)

EXE = test
LIB = libmylib.la

all: $(EXE) $(LIB)

clean:
    $(RM) *.o *.lo $(EXE) $(LIB)

$(EXE): $(EXE_OBJ)

$(LIB): $(LIB_OBJ)
    $(LIBTOOL) --tag=CXX --mode=link $(LINK.cc) -shared -version-info 1:0 -rpath $(shell readlink -f .) -o $@ $< $(LDLIBS)

%.o: %.cpp
    $(COMPILE.cc) -o $@ $<

%.lo: %.cpp
    $(LIBTOOL) --mode=compile --tag=CXX $(COMPILE.cc) -o $@ $<