C++ Statically linked shared library

Question

I have a shared library used by a another application beyond my control which requires *.so objects. My library makes use of sqlite3 which needs to be statically linked with it (I absolutely need a self-contained binary).

When I try to compile and link my library:

-fpic -flto -pthread -m64
-flto -static -shared

I end up with the following error:

/usr/bin/ld: /usr/local/lib/gcc/x86_64-unknown-linux-gnu/4.6.1/crtbeginT.o: relocation R_X86_64_32 against `__DTOR_END__' can not be used when making a shared object; recompile with -fPIC
/usr/local/lib/gcc/x86_64-unknown-linux-gnu/4.6.1/crtbeginT.o: could not read symbols: Bad value
collect2: ld returned 1 exit status

What is recompile with -fPIC related to? My code or CRT?

I have already tried to compile my object with -fPIC with the same result.

Thanks.

EDIT:

The problem does not seem to be related to SQLite3.

I wrote a simple one-line-do-nothing library which compiles and links like this:

g++ -c -fPIC -o bar.o bar.cpp
g++ -shared -o bar.so bar.o

but not like this:

g++ -c -fPIC -o bar.o bar.cpp
g++ -static -shared -o bar.so bar.o

The problem seems to be related to CRT (crtbeginT.o). Am I supposed to recompile GCC --with-pic or anything?

Answer 1

You shouldn't use the -static flag when creating a shared library, it's for creating statically linked executables.

If you only have a static version of the library, you can just link it in using -lsqlite3. But if there's both a dynamic version(.so) and a static version, the linker will prefer the dynamic one.

To instruct the linker to pick the static one, give the linker the -Bstatic flag, and make it switch back to dynamic linking for other stuff (like libc and dynamic runtime support) with -Bdynamic. That is, you use the flags:

 -Wl,-Bstatic -lsqlite3 -Wl,-Bdynamic  

Alternativly, you can just specify the full path of the .a file, e.g. /usr/lib/libsqlite3.a instead of any compiler/linker flags.

With the GNU ld, you can also use -l:libsqlite3.a instead of -lsqlite3. This will force the use of the library file libsqlite3.a instead of libsqlite3.so, which the linker prefers by default.

Remember to make sure the .a file have been compiled with the -fpic flag, otherwise you normally can't embed it in a shared library.

Answer 2

Any code that will somehow make its way into a dynamic library should be relocatable. It means that everything that is linked with your .so, no matter statically or dynamically, should be compiled with -fPIC. Specifically, static sqlite library should also be compiled with -fPIC.

Details of what PIC means are here: http://en.wikipedia.org/wiki/Position-independent_code