So I'm going nuts trying to figure this one out. Here's my basic setup:
I'm compiling a shared library with a bunch of core functionality that uses a lot of boost stuff. We'll call this library libpf_core.so. It's linked with the boost static libraries, specifically the python, system, filesystem, thread, and program_options libraries. This all goes swimmingly.
Now, I have a little test program called test_socketio which is compiled into a shared library (it's loaded as a plugin at runtime). It uses some boost stuff like boost::bind and boost::thread, and it's linked again libpf_core.so (which has the boost libraries included remember).
When I go to compile test_socketio though, out of all my plugins it gives me a linking error:
[ Building test_socketio ]
g++ -c -pg -g -O0 -I/usr/local/include -I../include test_socketio.cc -o test_socketio.o
g++ -shared test_socketio.o -lpy_core -o test_socketio.so
Undefined symbols:
"boost::lock_error::lock_error()", referenced from:
boost::unique_lock<boost::mutex>::lock() in test_socketio.o
ld: symbol(s) not found
collect2: ld returned 1 exit status
And I'm going crazy trying to figure out why this is. I've tried explicitly linking boost::thread into the plugin to no avail, tried ensuring that I'm using the boost headers associated with the libraries linked into libpf_core.so in case there was a conflict there.
Is there something OSX specific regarding boost that I'm missing? In my searching on google I've seen a number of other people get this error but no one seems to have come up with a satisfactory solution.
Edit: Figured it out, OSX comes with boost 1.40 in /usr/local/include. Needed to put the headers for my version of boost somewhere and make sure that my plugins sees those first.
You need to link to libboost_thread. Add the -lboost_thread switch.
When you link libpf_core.so against the static boost libraries, it's only going to get copies of the functions it actually uses. The linker doesn't bother to pull in functions that aren't referenced by the code in your library.
You need to link your test program against the boost libraries as well. You can't reliably "chain" the linkages.
Related
I am trying to compile my C++ project on Linux x64 with boost libraries 1.57.
This project is compiled with scons and I successfully compiled it on my Arch Linux, but this time failed on a Ubuntu machine.
I added -lboost_coroutine flag for linking but the error "undefined reference" still existed.
/usr/bin/g++ -o build/gcc.release/app -pthread -g
build/gcc.release/src/han/unity/rpcx.o
-lpthread -lz -lboost_coroutine -lboost_context -lboost_date_time
build/gcc.release/src/han/unity/rpcx.o: In function `attributes':
/usr/local/include/boost/coroutine/attributes.hpp:31: undefined reference
to `boost::coroutines::stack_traits::default_size()'
I noticed that the attributes.hpp is exactly one of the boost coroutine header files. And I tried with nm to boost coroutine libs and it seems no problem.
nm /usr/local/lib/libboost_coroutine.a | grep "default_size"
0000000000000170 T _ZN5boost10coroutines12stack_traits12default_sizeEv
I searched the possible reasons for this error and most are about the order of linker flags. And in this case the rpcx.o depends on boost_coroutine, so this appears in front.
What else could be the causes?
After several hours effort, I finally solved it.
That turns out to be the old boost (v1.55) lib still existing, which has static libraries with the same name of my manually installed boost library (v1.57). The linker found the v1.55 static libs before v1.57, so it used these libs for linking. However, in the old version, the function boost::coroutines::stack_traits::default_size() is still not introduced, which makes the linker cannot find the right location of this function, and returns "undefind reference".
For those who happens to find this questions from googling "undefined reference" errors during compiling, I got several steps about debugging this kind of problem and wrote here for your information.
Check if the library you linked with exists in /usr/lib/ or /usr/local/lib/, if not, try to install these first.
Check if you added the correct linking flag for your referred libs. For example, if you use boost_coroutine libs, be sure to add -lboost_coroutine during linking.
Check if the order of linking flags are correct (for gcc). This could be the cause of most cases. Make sure to put B in front of A if B depends on A.
Check if different versions exists for the same libraries.
I hope these could help somehow.
After battling my makefile woes I'm now onto problems with how the two libraries are supposed to interact. So, this is on Linux (CentOS 6.2 - 6.4, not that that seems to make much difference in terms of tools). The project, on the whole, is to be deployed in two flavors
A C++ Static library which is used for linking with other C++ appications (a *.a file)
A shared *.so which is deployed through python using Boost.python
I have everything compiling, but I'm not linking correctly somehow. In the case of the static library, it is built in two ways:
If meant to be linked with other C++ code, -fPIC is not used
If meant to be linked into the python module, use -fPIC
I control this through passing parameters to the make program. Presently, I'm trying to build the boost python module because the static stuff compiles just fine. So, I have dependencies on the boost libraries and zlib. The final linking command looks like this:
g++ -o pythonmod.so -L/boost/boost_libs -L/zlibs -lz -lboost_python -lboost_thread -lboost_regex -lboost_system /path/to/static.a -fPIC -shared [many_objects]
The "many_objects" comes from the various wrappers, and other code, that wraps the "pure" C++ from the boost.python layer in the code. Each of these object files are compiled with -fPIC as well. Their compiled with:
g++ -I/boost/boost_1_47 -I/usr/include/python2.6 -D _linux -MMD -std=c++0x -c -m32 -fPIC <input> -o <output>
The lines compiling the object files for the archive file look quite similar to the above only they do not include the python include directory.
I've found other links here to similar problems and tried the solutions but to no avail thus far. For example, this link uses -Wl,--whole-archive ... -Wl,--no-whole-archive. I tried this solution when I was trying to link in the static library archive before I was compiling it with -fPIC. Now that I'm doing that, I've tried this solution but also to no avail. In each case, every time I load up python and import the module, I get some sort of undefined symbol error --> something went wrong during linking.
How should I mix these libraries together to make the python module work?
After joining the gcc-help mailing list I received the pointer I needed to resolve the issue. The problem turned out to the ordering of the libraries used for linking on the build command line. Basically, the object files generated during the build for the *.so needed to be placed first. Then, the references to the boost and other libraries. Reordering the object files to reference the objects built for wrapping the static library before the other libraries was the key. No longer am I seeing weird "unresolved objects" when loading my python module.
After 4 or 5 years of using Visual Studio, my gcc knowledge had become sufficiently rusty that I'd forgotten the importance of ordering when it comes to linking.
I am trying to compile a program on my system with Debian Wheezy and g++4.7. I want it to be able to run on another system with Debian Squeeze (and no recent g++). I can't compile the program on the Squeeze, because I use certain C++11 features the old g++ does not support, as well as a new Boost version and libcrypto++9.
As far as I understand the usual way to get around this problem is to static link the libraries not supported at the other system, in my case libstdc, boost and crypto++.
My (linking) compiler call right now is
g++-4.7 .obj/btcmirco.o -Wl,-Bstatic -lboost_program_options -lboost_system -lcrypto++ -Wl,-Bdynamic -lcurl -static-libgcc -std=c++11 -o MyProgram
However I seem to have missed something, because it throws a lot of undefined reference errors. It works fine if I dynamic link to crypto++ (and only static link libstdc and boost).
Can anyone tell me whats wrong, or if there is a fundamental error in my approach?
The linker errors I get are (shorted):
`.text._ZN8CryptoPP22BufferedTransformationD2Ev' referenced in section `.text._ZN8CryptoPP22BufferedTransformationD1Ev[_ZN8CryptoPP22BufferedTransformationD1Ev]' of /usr/lib/gcc/x86_64-linux-gnu/4.7/../../../../lib/libcrypto++.a(cryptlib.o): defined in discarded section `.text._ZN8CryptoPP22BufferedTransformationD2Ev[_ZN8CryptoPP22BufferedTransformationD5Ev]' of /usr/lib/gcc/x86_64-linux-gnu/4.7/../../../../lib/libcrypto++.a(cryptlib.o)
`.text._ZN8CryptoPP25MessageAuthenticationCodeD2Ev' referenced in section `.text._ZN8CryptoPP25MessageAuthenticationCodeD1Ev[_ZN8CryptoPP25MessageAuthenticationCodeD1Ev]' of /usr/lib/gcc/x86_64-linux-gnu/4.7/../../../../lib/libcrypto++.a(cryptlib.o): defined in discarded section `.text._ZN8CryptoPP25MessageAuthenticationCodeD2Ev[_ZN8CryptoPP25MessageAuthenticationCodeD5Ev]' of /usr/lib/gcc/x86_64-linux-gnu/4.7/../../../../lib/libcrypto++.a(cryptlib.o)
I experienced the same problem and this has to do with the fact that you are trying to mix code generated by g++-4.7 (your program) with code generated by a previous version of g++ (cryptopp library).
The reason behind this is that when you execute compile the library executing make command, it uses the default version of g++ set up for your system, usually the one that comes with the OS.
In order to solve the issue what you should do is compile cryptopp library with g++-4.7.
For that, compile the library by executing make CXX=g++-4.7. The resulting static library shouldn't give you the error when being linked with your code.
I have a problem, i want to compile my application with static linking of mysql connector.
My command line:
g++ -o newserver stdafx.cpp ... -lboost_system -lboost_thread
-lpthread -lmysqlcppconn -static /usr/lib/libmysqlcppconn-static.a -std=c++0x
But i have error:
/usr/bin/ld: cannot find -lmysqlcppconn
/tmp/ccxpOfdZ.o: In function `IsEqualsDns(unsigned long, std::basic_string<char, std::char_traits<char>, std::allocator<char> >)':
Server.cpp:(.text+0x356e): warning: Using 'gethostbyname' in statically linked applications requires at runtime the shared libraries from the glibc version used for linking
collect2: ld returned 1 exit status
How can i fix this?
Thanks!
Where is the library libsqlcppconn.a or libsqucppconn.so
(static or dynamic)? The compiler is looking for it, and
doesn't find it.
Presumably, this is the same library as
/usr/lib/mysqlcppconn-static.a. If so, just drop the
-lmysqlcppconn. Or just use -lmysqlcppconn-static (no
spaces), and forget about the /usr/lib/libmysqlconn-static.a.
With a name like that, there shouldn't be a corresponding .so,
which means that g++ will link it statically, even without the
-static. You only need the -static if there is both
a libmysqlconn-static.so and a libmysqlconn-static.a in the
same directory.
With regards to the second error (which is just a warning, but
will cause problems if you try to run the linked program on
other machines, or even after an upgrade of your machine): if
you use -static anywhere in your command line (as you
currently do), then it applies to all files linked afterwards.
Including the system libraries, which you don't want to link
statically. My guess is that the -static isn't necessary (see
above); if it is, place it immediately before the library you
want to link statically, and place a -dynamic immediately
after (so that any following libraries, including the system
libraries, will be dynamically linked).
You could try g++ -static YOUR ARGUMENTS.
If you are coming from a Windows platform, linking against Boost can give a few surprises. The typicall Boost installation (e.g. after ./b2 install) will make both dynamic and static libraries and put them in the same directory. Typically, the two library forms only differ in their extension (.so or .a).
Windows supports auto-linking, which basically means that library files contain some flags in their first few bytes indicating whether they are for dynamic or for static linking. On Linux platforms, this is not the case and the linker gets confused which file to load (since you don't provide the extension of the library name). Therefore, you need to tell your linker which form of linking you want.
I would like to utilize the UnitTest++ library in a testing file. However, I am having some difficulty getting the library to be included at compile time. So here is my current directory structure:
tests/
UnitTests++/
libUnitTest++.a
src/
UnitTests++.h
unit/
test.cpp
I have just used the UnitTest++ getting started guide to just get the library setup. Here is test.cpp:
// test.cpp
#include <UnitTest++.h>
TEST(FailSpectacularly)
{
CHECK(false);
}
int main()
{
return UnitTest::RunAllTests();
}
And I am currently trying to compile with:
gcc -lUnitTest++ -L../UnitTest++/ -I../UnitTest++/src/ test.cpp
I am currently getting a bunch output with ld: symbol(s) not found at the end. So how would I be able to get the UnitTest++ library properly included when this program is compiled? I am on a Mac and I'd also like for there to be an easy way for people on a Linux machine to run these same tests.
Whew, I hope this provides enough information, if not please let me know.
I was able to build it in the following manner
gcc -L../UnitTest++/ -I../UnitTest++/src/ test.cpp -lUnitTest++ -lstdc++
or
g++ -L../UnitTest++/ -I../UnitTest++/src/ test.cpp -lUnitTest++
that links to libstdc++ automatically.
GCC documentation says:
-llibrary
-l library
Search the library named library when linking. (The second alternative with the library as a separate argument is only for POSIX compliance and is not recommended.)
It makes a difference where in the command you write this option; the linker searches and processes libraries and object files in the order they are specified.
Thus, foo.o -lz bar.o' searches libraryz' after file foo.o but before bar.o. If bar.o refers to functions in `z', those functions may not be loaded.
I guess that's why the library symbols are not found when you first specify -lUnitTest++ and then test.cpp
Compile test.cpp to get test.o
and use
g++ test.o libUnitTest++.a -o ./exectest
to get the ./exectest executable
libUnitTest++.a is just an archive of all the object files of UnitTest++. You just need to link all the object files (your test object file + libUnitTest++.a)
Try editing the makefile that came with unittest++ and make it suitable for your case
The message ld: symbol(s) not found means you haven't compiled the library. So you need to go in the UnitTest++ folder, compile and install it.
I've never worked on a MAC, but in linux, libraries are usually compiled and installed with:
./configure
make
make install
In the UnitTest++ link you posted, you should simply:
make install
Then you will have the UnitTest++.so library in the libraries folder of your OS. Now the library can be linked with your program with the -lUnitTest++ command.
Usually you have to put -Lsomething before the -lsomething that requires it.