linux linking to a .so , but still getting undefined reference - c++

Question

I am trying to create an executable that uses code from both static libraries and a shared library:
The static libs are several boost .a , pthread and libbus.a. The shared lib is a libwrap.so.
Note that the libwrap , uses code from libbus and libbus uses code from pthread. Finally, the executable uses code from libwrap and from boost.
Since the order of libraries included in the linker matters I am trying to find the "winning" sequence.
The linking stage is the following (pasted in multiple lines for convenience):
$ /usr/bin/c++
-Wall -Wextra
-fPIC
-fvisibility=hidden -fno-strict-aliasing -Wno-long-long
-m64
-rdynamic
-D_UNICODE -DUNICODE
CMakeFiles/Wrapper_Test.dir/test.cpp.o
/usr/local/lib/libboost_log.a
/usr/local/lib/libboost_system.a
/usr/local/lib/libboost_filesystem.a
/usr/local/lib/libboost_date_time.a
/usr/local/lib/libboost_thread.a
/usr/local/lib/libboost_log_setup.a
/usr/local/lib/libboost_chrono.a
-pthread
/home/nass/dev/Data_Parser/trunk/external/lib/linux64_gcc_release/libbus.a
-L/home/nass/dev/Data_Parser_build/lib #this is where the libwrap.so is located
-Wl,-rpath,/home/nass/dev/Data_Parser_build/lib
-lwrap #the shared lib
-o ../../../bin/Wrapper_Test
The link error is
CMakeFiles/Wrapper_Test.dir/test.cpp.o: In function `main':
test.cpp:(.text+0x2e): undefined reference to `wrapperNamespace::GetWrapper()'
collect2: error: ld returned 1 exit status
The GetWrapper() is located in libwrap.so of course, and I can verify it is a symbol that can be found in there:
$ nm -Ca ../../../lib/libwrap.so | grep GetWrapper
00000000000423d6 t wrapperNamespace::GetWrapper()
However, the linker cannot find it. what am I doing wrong here?
EDIT:
The linking command above is generated by the following CMakeLists.txt file:
set(TARGET_NAME Wrapper_Test)
#set(CMAKE_BINARY_DIR ${CMAKE_SOURCE_DIR}/bin)
#set(EXECUTABLE_OUTPUT_PATH ${CMAKE_BINARY_DIR})
#set(LIBRARY_OUTPUT_PATH ${CMAKE_BINARY_DIR})
# INCLUDE INTERNAL FOLDER
include_directories(${CMAKE_SOURCE_DIR}/include/Wrapper)
add_executable(${TARGET_NAME} test.cpp)
add_boost_lib(${TARGET_NAME} log system filesystem date_time thread log_setup chrono)
setup_libbus(${TARGET_NAME}) #the libbus.a
target_link_libraries(${TARGET_NAME} -L../../../lib -lwrap)
set_property(TARGET ${TARGET_NAME} PROPERTY FOLDER test)

Answer 1

I would start by looking at the cmake file which generates these lines.
It should be simple to add shared libaries to your path, for example:
find_library(
LIBWrapper
NAMES wrap
PATHS /home/nass/dev/Data_Parser_build/lib
)
And then link them to your test file, for example
add_executable(test src/test.cpp)
target_link_libraries(test ${LIBWrapper})
Similar should work for static libraries. This has the advantage that you don't have to deal with all the compiler/platform specific details which CMake supposedly handles for you, and which can be fairly complex & obscure.
If your library is generated dynamically, i.e. before cmake configuration time, you could just pass the appropriate linking flags to target_link_libraries:
target_link_libraries(test -L/home/nass/dev/Data_Parser_build/lib -lwrap)
I have used this suggestion in a few projects (e.g. https://github.com/caskorg/cask/blob/master/CMakeLists.txt) which dynamically generate the library, then link against it. If this doesn't work I suspect something else is wrong.

Answer 2

You should use -Wl,-Bstatic in front of static libs and -Wl,-Bdynamic for the dynamic ones. You also need to use -l for libraries and -L for library paths.
Something like:
$ /usr/bin/c++ test.cpp.o \
-L/usr/local/lib \
-Wl,-Bstatic \
-lboost_log \
-lsystem \
-L/home/nass/dev/Data_Parser_build/lib \
-Wl-Bdynamic \
-Wl,-rpath,/home/nass/dev/Data_Parser_build/lib \
-lwrap \
-o ../../../bin/Wrapper_Test
looks better. Many things depend on the version of your compiler/linker/OS.