Runtime "symbol lookup error" after compilation and linking of .so - c++

Question

first of all I've searched this one quite a bit and haven't managed to find a question with the same situation.
I'm building a 32 bit plugin as a shared-object on a 64 bit machine and using cpp-redis. cpp-redis built fine and I used a cmake toolchain to force 32 bit, checked the .o files during build and confirmed they are 32 bit.
I compiled and linked my very basic program (consisting of one main source file and an extra lib for talking to my host application since this is a plugin).
Upon running loading the plugin into the host app, I am greeted with:
symbol lookup error: plugins/samp-redis.so: undefined symbol: _ZN9cpp_redis16redis_subscriberC1ERKSt10shared_ptrINS_7network10io_serviceEE
I'm pretty stumped as I've added the cpp-redis dir to the linker path with -L and the library with -l, here's my comp/link lines:
(SDK_DIR is my host app sdk, pretty small and minimal set of .c/h files)
g++ -fpermissive -fPIC -m32 -std=c++11 -c -O3 -w -D LINUX -I$(SDK_DIR) -I$(SDK_DIR)/amx -I/usr/local/include/cpp_redis (source .cpp files...)
g++ -v -Wall -O2 -m32 -fshort-wchar -s -shared -L/usr/local/lib/ -lcpp_redis -o $(OUTFILE) *.o
Which runs fine with no errors, I ran the link stage with -v to check the flags went in properly and it all looks fine.
(added some newlines for readability)
Using built-in specs.
COLLECT_GCC=g++
COLLECT_LTO_WRAPPER=/usr/lib/gcc/x86_64-linux-gnu/4.9/lto-wrapper
Target: x86_64-linux-gnu
Configured with: ../src/configure
-v
--with-pkgversion='Debian 4.9.2-10'
--with-bugurl=file:///usr/share/doc/gcc-4.9/README.Bugs
--enable-languages=c,c++,java,go,d,fortran,objc,obj-c++
--prefix=/usr
--program-suffix=-4.9
--enable-shared
--enable-linker-build-id
--libexecdir=/usr/lib
--without-included-gettext
--enable-threads=posix
--with-gxx-include-dir=/usr/include/c++/4.9
--libdir=/usr/lib
--enable-nls
--with-sysroot=/
--enable-clocale=gnu
--enable-libstdcxx-debug
--enable-libstdcxx-time=yes
--enable-gnu-unique-object
--disable-vtable-verify
--enable-plugin
--with-system-zlib
--disable-browser-plugin
--enable-java-awt=gtk
--enable-gtk-cairo
--with-java-home=/usr/lib/jvm/java-1.5.0-gcj-4.9-amd64/jre
--enable-java-home
--with-jvm-root-dir=/usr/lib/jvm/java-1.5.0-gcj-4.9-amd64
--with-jvm-jar-dir=/usr/lib/jvm-exports/java-1.5.0-gcj-4.9-amd64
--with-arch-directory=amd64
--with-ecj-jar=/usr/share/java/eclipse-ecj.jar
--enable-objc-gc
--enable-multiarch
--with-arch-32=i586
--with-abi=m64
--with-multilib-list=m32,m64,mx32
--enable-multilib
--with-tune=generic
--enable-checking=release
--build=x86_64-linux-gnu
--host=x86_64-linux-gnu
--target=x86_64-linux-gnu
Thread model: posix
gcc version 4.9.2 (Debian 4.9.2-10)
COMPILER_PATH=/usr/lib/gcc/x86_64-linux-gnu/4.9/
:/usr/lib/gcc/x86_64-linux-gnu/4.9/
:/usr/lib/gcc/x86_64-linux-gnu/
:/usr/lib/gcc/x86_64-linux-gnu/4.9/
:/usr/lib/gcc/x86_64-linux-gnu/
LIBRARY_PATH=/usr/lib/gcc/x86_64-linux-gnu/4.9/32/
:/usr/lib/gcc/x86_64-linux-gnu/4.9/../../../../lib32/
:/lib/../lib32/
:/usr/lib/../lib32/
:/usr/lib/gcc/x86_64-linux-gnu/4.9/
:/usr/lib/gcc/x86_64-linux-gnu/4.9/../../../
:/lib/
:/usr/lib/
COLLECT_GCC_OPTIONS='-v' '-Wall' '-O2' '-m32' '-fshort-wchar' '-s' '-shared' '-L/usr/local/lib/' '-o' 'samp-redis.so' '-shared-libgcc' '-mtune=generic' '-march=i586'
/usr/lib/gcc/x86_64-linux-gnu/4.9/collect2
-plugin /usr/lib/gcc/x86_64-linux-gnu/4.9/liblto_plugin.so
-plugin-opt=/usr/lib/gcc/x86_64-linux-gnu/4.9/lto-wrapper
-plugin-opt=-fresolution=/tmp/cc0Lo5po.res
-plugin-opt=-pass-through=-lgcc_s
-plugin-opt=-pass-through=-lc
-plugin-opt=-pass-through=-lgcc_s
--sysroot=/
--build-id
--eh-frame-hdr
-m elf_i386
--hash-style=gnu
-shared
-o samp-redis.so
-s /usr/lib/gcc/x86_64-linux-gnu/4.9/../../../../lib32/crti.o /usr/lib/gcc/x86_64-linux-gnu/4.9/32/crtbeginS.o
-L/usr/local/lib/
-L/usr/lib/gcc/x86_64-linux-gnu/4.9/32
-L/usr/lib/gcc/x86_64-linux-gnu/4.9/../../../../lib32
-L/lib/../lib32
-L/usr/lib/../lib32
-L/usr/lib/gcc/x86_64-linux-gnu/4.9
-L/usr/lib/gcc/x86_64-linux-gnu/4.9/../../..
-lcpp_redis amxplugin2.o amxplugin.o main.o
-lstdc++
-lm
-lgcc_s
-lc
-lgcc_s /usr/lib/gcc/x86_64-linux-gnu/4.9/32/crtendS.o /usr/lib/gcc/x86_64-linux-gnu/4.9/../../../../lib32/crtn.o
Am I misunderstanding the linking stage or statically linking? It has been a while since I did C++... I'm all about Python and Go these days!
EDIT:
Compiling with -W,--no-undefined results in this output:
Using built-in specs.
COLLECT_GCC=g++
COLLECT_LTO_WRAPPER=/usr/lib/gcc/x86_64-linux-gnu/4.9/lto-wrapper
Target: x86_64-linux-gnu
Configured with: ../src/configure
-v
--with-pkgversion='Debian 4.9.2-10'
--with-bugurl=file:///usr/share/doc/gcc-4.9/README.Bugs
--enable-languages=c,c++,java,go,d,fortran,objc,obj-c++
--prefix=/usr
--program-suffix=-4.9
--enable-shared
--enable-linker-build-id
--libexecdir=/usr/lib
--without-included-gettext
--enable-threads=posix
--with-gxx-include-dir=/usr/include/c++/4.9
--libdir=/usr/lib
--enable-nls
--with-sysroot=/
--enable-clocale=gnu
--enable-libstdcxx-debug
--enable-libstdcxx-time=yes
--enable-gnu-unique-object
--disable-vtable-verify
--enable-plugin
--with-system-zlib
--disable-browser-plugin
--enable-java-awt=gtk
--enable-gtk-cairo
--with-java-home=/usr/lib/jvm/java-1.5.0-gcj-4.9-amd64/jre
--enable-java-home
--with-jvm-root-dir=/usr/lib/jvm/java-1.5.0-gcj-4.9-amd64
--with-jvm-jar-dir=/usr/lib/jvm-exports/java-1.5.0-gcj-4.9-amd64
--with-arch-directory=amd64
--with-ecj-jar=/usr/share/java/eclipse-ecj.jar
--enable-objc-gc
--enable-multiarch
--with-arch-32=i586
--with-abi=m64
--with-multilib-list=m32,m64,mx32
--enable-multilib
--with-tune=generic
--enable-checking=release
--build=x86_64-linux-gnu
--host=x86_64-linux-gnu
--target=x86_64-linux-gnu
Thread model: posix
gcc version 4.9.2 (Debian 4.9.2-10)
COMPILER_PATH=/usr/lib/gcc/x86_64-linux-gnu/4.9/
:/usr/lib/gcc/x86_64-linux-gnu/4.9/
:/usr/lib/gcc/x86_64-linux-gnu/
:/usr/lib/gcc/x86_64-linux-gnu/4.9/
:/usr/lib/gcc/x86_64-linux-gnu/
LIBRARY_PATH=/usr/lib/gcc/x86_64-linux-gnu/4.9/32/
:/usr/lib/gcc/x86_64-linux-gnu/4.9/../../../../lib32/
:/lib/../lib32/
:/usr/lib/../lib32/
:/usr/lib/gcc/x86_64-linux-gnu/4.9/
:/usr/lib/gcc/x86_64-linux-gnu/4.9/../../../
:/lib/
:/usr/lib/
COLLECT_GCC_OPTIONS='-v' '-Wall' '-O2' '-m32' '-fshort-wchar' '-s' '-shared' '-L/usr/local/lib/' '-o' 'samp-redis.so' '-shared-libgcc' '-mtune=generic' '-march=i586'
/usr/lib/gcc/x86_64-linux-gnu/4.9/collect2
-plugin /usr/lib/gcc/x86_64-linux-gnu/4.9/liblto_plugin.so
-plugin-opt=/usr/lib/gcc/x86_64-linux-gnu/4.9/lto-wrapper
-plugin-opt=-fresolution=/tmp/ccOq8qY8.res
-plugin-opt=-pass-through=-lgcc_s
-plugin-opt=-pass-through=-lc
-plugin-opt=-pass-through=-lgcc_s
--sysroot=/
--build-id
--eh-frame-hdr
-m elf_i386
--hash-style=gnu
-shared
-o samp-redis.so
-s /usr/lib/gcc/x86_64-linux-gnu/4.9/../../../../lib32/crti.o /usr/lib/gcc/x86_64-linux-gnu/4.9/32/crtbeginS.o
-L/usr/local/lib/
-L/usr/lib/gcc/x86_64-linux-gnu/4.9/32
-L/usr/lib/gcc/x86_64-linux-gnu/4.9/../../../../lib32
-L/lib/../lib32
-L/usr/lib/../lib32
-L/usr/lib/gcc/x86_64-linux-gnu/4.9
-L/usr/lib/gcc/x86_64-linux-gnu/4.9/../../..
-Bstatic
--no-undefined
-lcpp_redis amxplugin.o amxplugin2.o main.o
-lstdc++
-lm
-lgcc_s
-lc
-lgcc_s /usr/lib/gcc/x86_64-linux-gnu/4.9/32/crtendS.o /usr/lib/gcc/x86_64-linux-gnu/4.9/../../../../lib32/crtn.o
/usr/bin/ld: cannot find
-lgcc_s
/usr/bin/ld: cannot find
-lgcc_s
collect2: error: ld returned 1 exit status
makefile:15: recipe for target 'build' failed
make: *** [build] Error 1
Apparently it can't find gcc_s whatever that is? s=static?
I tried searching for gcc libs:
$ find /usr/ -name libgcc*
/usr/lib/gcc/x86_64-linux-gnu/4.9/libgcc_s.so
/usr/lib/gcc/x86_64-linux-gnu/4.9/libgcc_eh.a
/usr/lib/gcc/x86_64-linux-gnu/4.9/x32/libgcc_s.so
/usr/lib/gcc/x86_64-linux-gnu/4.9/x32/libgcc_eh.a
/usr/lib/gcc/x86_64-linux-gnu/4.9/x32/libgcc.a
/usr/lib/gcc/x86_64-linux-gnu/4.9/libgcc.a
/usr/lib/gcc/x86_64-linux-gnu/4.9/32/libgcc_s.so
/usr/lib/gcc/x86_64-linux-gnu/4.9/32/libgcc_eh.a
/usr/lib/gcc/x86_64-linux-gnu/4.9/32/libgcc.a
/usr/lib/gcc/x86_64-linux-gnu/4.9/libgcc_s_32.so
/usr/lib/gcc/x86_64-linux-gnu/4.9/libgcc_s_x32.so
/usr/lib/gcc/x86_64-linux-gnu/4.8/libgcc_s.so
/usr/lib/gcc/x86_64-linux-gnu/4.8/libgcc_eh.a
/usr/lib/gcc/x86_64-linux-gnu/4.8/libgcc.a
/usr/lib/x86_64-linux-gnu/libgccpp.so.1
/usr/lib/x86_64-linux-gnu/libgccpp.so.1.0.3
Yet doing a ldconfig search shows files named libgcc.so.1:
$ sudo /sbin/ldconfig -p | grep libgcc
libgccpp.so.1 (libc6,x86-64) => /usr/lib/x86_64-linux-gnu/libgccpp.so.1
libgcc_s.so.1 (libc6,x32) => /usr/libx32/libgcc_s.so.1
libgcc_s.so.1 (libc6,x86-64) => /lib/x86_64-linux-gnu/libgcc_s.so.1
libgcc_s.so.1 (libc6) => /usr/lib32/libgcc_s.so.1
Could this be the reason?
And googling the error brings up some results so I'll keep digging...

Answer 1

Even if you build cpp_redis as static library for it to be linkable with shared library it must be compiled with -fPIC flag ie code must be relocatable. Looks like in your case linker silently ignores incompatible code when linking shared lib. You can check if symbols from cpp_redis resolved into your plugin by running nm with your .so file.
According to your update, you should link your plugin with -W,--no-undefined not cpp_redis. Most probably it will fail as symbols from host program would be missing. But you can check if symbols from cpp_redis are listed as missing or not.