Self-Contained C Shared Library

Question

I am currently developing a C library for a client and to do so I needed to use other libraries like: glib2.0, libxml2, lib, openssl and gmp. After I finished my development and created the .so I tried to compile a test program with it and found out that my library was not self-contained and that I needed to link the program with all those other libraries I mentioned above.

The client insist that he wants either a dll or a .so product and that it should be self contained, just one file so his application can consume it, the same way that he does with other libraries.

I am not sure what to do, it there a way to produced this self contained .so? If not possible what other options do I have? I am developing in solaris 11 and the target system is a Solaris server.

Thank you very much.

Makefile code:

# C compiler 
CC = gcc 

# C flags
CFLAGS = -fPIC -O3 -g 

# linking flags
LDFLAGS = -shared 
LDLIBS = $(shell xml2-config --cflags --libs) $(shell pkg-config --cflags --libs glib-2.0) -lssl -lcrypto -lm -lgmp -lz 

# target lib
TARGET_LIB = libservices.so
SRCS = lib1.c lib2.c lib3.c lib4.c # source files

OBJS = $(SRCS:.c=.o)
# Compilation 
.PHONY: all
all: ${TARGET_LIB}

$(TARGET_LIB): $(OBJS) 
    ${CC} ${LDFLAGS} $(OBJS) -o ${TARGET_LIB}

# pull in dependency info for *existing* .o files
-include $(OBJS:.o=.d)

# Compiles and Generates Dependency Info
%.o: %.c
    gcc $(CFLAGS) -c $*.c -o $*.o ${LDLIBS}
    gcc -MM $(CFLAGS) $*.c > $*.d

Example output of test code compilation

gcc -I/path/to/libservices -L/path/to/libservices services_test.c -o test -lservices

libservices.so: undefined reference to `EVP_CipherInit'
libservices.so: undefined reference to `g_free'
libservices.so: undefined reference to `xmlFreeDoc'
libservices.so: undefined reference to `g_str_equal'
libservices.so: undefined reference to `g_hash_table_lookup'
libservices.so: undefined reference to `__gmpz_get_str'
libservices.so: undefined reference to `EVP_CIPHER_CTX_block_size'
libservices.so: undefined reference to `xmlCheckVersion'
libservices.so: undefined reference to `EVP_EncryptFinal'
libservices.so: undefined reference to `g_hash_table_new'
libservices.so: undefined reference to `EVP_CIPHER_CTX_init'
libservices.so: undefined reference to `xmlNodeGetContent'
libservices.so: undefined reference to `xmlCleanupParser'
libservices.so: undefined reference to `__gmpz_pow_ui'
libservices.so: undefined reference to `EVP_EncryptUpdate'
libservices.so: undefined reference to `__gmpz_clear'
libservices.so: undefined reference to `xmlParseDoc'
libservices.so: undefined reference to `g_hash_table_insert'
libservices.so: undefined reference to `EVP_DecryptInit_ex'
libservices.so: undefined reference to `EVP_EncryptInit_ex'
libservices.so: undefined reference to `g_hash_table_destroy'
libservices.so: undefined reference to `g_list_free'
libservices.so: undefined reference to `EVP_DecryptFinal'
libservices.so: undefined reference to `g_str_hash'
libservices.so: undefined reference to `__gmpz_init_set_str'
libservices.so: undefined reference to `EVP_DecryptUpdate'
libservices.so: undefined reference to `EVP_CipherFinal'
libservices.so: undefined reference to `__gmpz_sizeinbase'
libservices.so: undefined reference to `xmlDocGetRootElement'
libservices.so: undefined reference to `g_hash_table_foreach'
libservices.so: undefined reference to `EVP_CIPHER_CTX_cleanup'
libservices.so: undefined reference to `EVP_CipherUpdate'
collect2: error: ld returned 1 exit status

If I link it with the other libraries doing:

gcc -I/path/to/libservices -L/path/to/libservices servicios_test.c -o test -lservices -lssl -lcrypto -lm -lgmp -lz `pkg-config --cflags --libs glib-2.0` `xml2-config --cflags --libs`

And then add the path using:

export LD_LIBRARY_PATH=/path/to/libservices:$LD_LIBRARY_PATH

the test code works fine.

Answer 1

I think you are more or less done.

The whole point of shared libraries is to not include anything from any other library dependencies. That's the job of the runtime linker, not the compile-time linker.

Since the application apparently depends on other libraries already, your library, and any additional libraries your library depends on but which the application does not already depend on, are just more libraries to add to the list.

Answer 2

In theory it is possible but I can't think of a reasonable reason to go on that path. Also it would be quite hard to do it. In terms of code here's what you should do:

LDLIBS = $(shell xml2-config --cflags --libs) $(shell pkg-config --cflags --libs glib-2.0) -Bstatic -lssl -lcrypto -lm -lgmp -lz

By adding -Bstatic, you instruct the linker to use the static versions of the libraries that follow. But there's a catch: the static version of the libraries must exist on the system that you compile your .so on. Some of them might exist by default, but you'll have to do extra work:

• libm, libgmp, libz - most likely there are packages in the os that have the static version of those, you have to install them (usually the package names are lib${LIBNAME}-static or lib${LIBNAME}-devel)
• for libcrypto and libssl, you'll have to recompile OpenSSL as static libraries.