I am compiling a C++ application using GNU g++. The project takes advantage of OpenSSL libraries.
Background
On my machine (a 64 bit CentOS quad core) I compile and link my files.
g++ -g -c -L/usr/local/lib/ -L/usr/lib64/
-I/usr/local/include/ -I/usr/local/ssl/include/
-lcrypto mysrc1.cpp mysrc2.cpp mysrc3.cpp
g++ -L/usr/local/lib/ -L/usr/lib64/ -lcrypto
*.o -o ./myapp.out
My application uses function MD5 which is contained in libcrypto.so. As you can see I specify to g++ the dirs where to search using the -L, -I options and which libraries to look for with the -l<lib-name> option. There are some trivial paths like /usr/local/lib which can be omitted of course, but I specified them because the makefile is parametric.
The problem
My problem is that I can successfully compile my stuff (first command), but linking fails (second command):
/usr/bin/ld: cannot find -lcrypto
collect2: ld returned 1 exit status
make: * [cppsims_par] Error 1
But I did check folders and everything... libcrypto.so is inside /usr/lib64/. What is going on?
It may help if you try strace to find why it failed the file lookup
strace -f -e trace=file g++ -L/usr/local/lib/ -L/usr/lib64/ -lcrypto
*.o -o ./myapp.out
I did find the problem and it is related to this question: ld cannot find an existing library
Actually I had no symlink libcrypto.so and the compiler was not able to find the library...
I had related issue, and resolved it after inspecting the trace.
I had
-L<my/path/to/lib> -llib_some_library
when it should have been
-L<my/path/to/lib> -lsome_library
Related
I am compiling an opensource project to run on my machine which is this project. It requires boost library so I installed the Boost_1_55 library on my ubuntu machine but the compiling process was not successfully finished by printing out some error messages as follows.
libtool: link: g++ -g -O3 -Wall -DKENLM_MAX_ORDER=6 -W -Wall -Wno-sign-compare -I./.. -pthread -I/usr/include -g -O2 -o .libs/query query_main.o ./.libs/libklm.so ../util/.libs/libklm_util.so -lz -L/usr/lib/x86_64-linux-gnu -lboost_program_options -lboost_thread -lboost_system -lpthread -lrt -pthread
../util/.libs/libklm_util.so: undefined reference to `boost::thread::join()'
../util/.libs/libklm_util.so: undefined reference to `boost::thread::~thread()'
./.libs/libklm.so: undefined reference to `boost::thread::start_thread()'
collect2: ld returned 1 exit status
This answer seems the solution for my problem but the result of ls -al /usr/local/lib | grep thread showed me like below.
libboost_thread.a
libboost_thread.so -> libboost_thread.so.1.55.0
libboost_thread.so.1.49.0
libboost_thread.so.1.55.0
I don't know what else to check more. Thank you in advance for your help.
You can try to add /usr/local/lib to LD_LIBRARY_PATH like this
export LD_LIBRARY_PATH=/usr/local/lib:$LD_LIBRARY_PATH
You have the static Boost library object (libboost_thread.so) but do you have the Boost development files installed? Check to see if the /usr/include/boost/thread directory exists and has *.hpp files in it. If not you may need to install the libboost-thread-dev package for your distribution or download the header files directly from Boost.org.
I'm trying to use X86_64-w64-mingw32-g++ (packaged in Archlinux's MingW package) to cross compile some C++ code into an Windows executable, however I'm having trouble getting past some issues.
I'm calling
x86_64-w64-mingw32-g++ -o build_win/asm build_win/asm.o build_win/asm_lib.o build_win/socket_boost.o -I../extra/etc -fopenmp -lrt -std=c++11 -g -lboost_system -lboost_serialization
from a makefile, but I get thrown the errors:
/usr/lib/gcc/x86_64-w64-mingw32/5.1.0/../../../../x86_64-w64-mingw32/bin/ld: cannot find -lrt
/usr/lib/gcc/x86_64-w64-mingw32/5.1.0/../../../../x86_64-w64-mingw32/bin/ld: cannot find -lboost_system
/usr/lib/gcc/x86_64-w64-mingw32/5.1.0/../../../../x86_64-w64-mingw32/bin/ld: cannot find -lboost_serialization
This works fine with native g++, so exactly do I have to change for mingw to compile?
EDIT: I have mingw-w64-boost package installed, which includes boost libraries pre-compiled and ready to be linked. However, it seems the naming convention is a bit different, and -lboost_system for example becomes -llibboost_system-mt (not exactly sure what the -mt suffix entails).
Problem is I can't find the mingw counterpart for -lrt. I've tried with both -lrtm and -lrtutils but in both cases I get:
[...]
undefined reference to `__imp_getsockopt'
Are you sure that -lboost_system and other libraries are present in the same directory as makefile ?
If not then please include -L flag which indicates the location of your library.
For example:
-L /path_openmp -fopenmp -L /path_boost_system/ -lboost_system -L /path_serialization -lboost_serialization
Moreover, you need not include -I and -g flag when creating an executable from .o files. These are needed when you create .o from .cpp files.
There is no rt library on Windows.
You are missing -lws2_32.
$ x86_64-w64-mingw32-nm -A /usr/x86_64-w64-mingw32/lib/*.a 2>/dev/null | grep getsockopt | grep " T "
I am trying to link a project with the following command:
g++ build/test.o -o bin/test -pthread -L lib -L /home/alexander/opt/lib -lboost_thread-mt
which results in the following errors:
/usr/bin/ld: cannot find -lboost_thread-mt
collect2: error: ld returned 1 exit status
However, the boost libraries are installed in the directory /home/alexander/opt/lib. Why does the linker do not find the boost libraries? I also tried to link with -I instead if -L with the same outcome...
Content of /home/alexander/opt/lib is /home/alexander/opt/lib/boost_1_57_0.
change libboost_thread-mt to libboost_thread, first find the address of libboost_thread.so and libboost_thread.a then make softlinks to these files in the same address,
so it should be:
ln -s /...libboostSourceFiles.../libboost_thread.so /..RequestTOmtFiles.../libboost_thread-mt.so
it works for other libboost -mt files too, like serialization , iostreams, programoptions
I would like to create a dynamic library for c++ program on linux.
In c++ program/system I`m using libconfig++ library, libpqxx library, some boost and c++11.
My steps:
1)
g++ -Wall -I/usr/local/include/ -std=c++0x -lconfig++ -Wall -lpqxx -lpq -fPIC -c ../SourceFiles/DBHandler.cpp ../SourceFiles/ParamServer.cpp ../SourceFiles/Functions.cpp
2)
g++ -shared -Wl,-soname,libctest.so.1 -o libctest.so.1.0 *.o
3)
ln -sf libctest.so.1.0 libctest.so.1
4)
ln -sf libctest.so.1.0 libctest.so
5) compile
g++ -Wall -I/path/to/include-files -L/path/to/libraries program.cpp -I/usr/local/include/ -std=c++0x -lconfig++ -lpqxx -lpq -lctest -o prog
After execute above command :
/usr/bin/ld: cannot find -lctest
collect2: ld returned 1 exit status
What am I doing wrong?
Here is the reference:
enter link description here
In step 5, you forgot -L. to look for libraries in the current directory.
By default, only a [long] list of system directories is used when searching for libraries.
You will also need to add . to the LD_LIBRARY_PATH environment variable before executing your program, so that the current directory is searched at runtime, too. Running ldconfig will avoid this, but if you are only testing your library and do not want to persistently affect your system, I would stick to the LD_LIBRARY_PATH approach.
An alternative is to "install" your library into one of those directories, such as /usr/local/lib (or your equivalent). You should use ldconfig after doing this, so that the dynamic library cache and all your symlinks are set up for you. This is the canonical approach but may not be suitable during iterative development of said library.
You need to ldconfig update the dynamic library cache -- it will also create the symbolic links for you.
See eg Section 3.5 of this Linux Documentation Project HOWTO
I am trying to build some software on a brand new install of CentOS 5.5
My compile line is :
g++ -I ../common/ -I ../readers/ -I ../writers/ -I /home/dcole/software/xerces-c-3.1.1/src -O3 -Wall -fopenmp -fPIC -o chipper chipper.cpp -L/usr/lib64/ ../../lib/IDT.a ../../lib/Linux/libxerces-c.a -lcurl -lidn -ldl -lssl ../../lib/Linux/libfftw3f.a -lpthread -lm
and I am getting
[exec] /usr/bin/ld: cannot find -lcurl
[exec] collect2: ld returned 1 exit status
Even though I can actually see the lib
$ /sbin/ldconfig -p | grep curl
libcurl.so.3 (libc6,x86-64) => /usr/lib64/libcurl.so.3
libcurl.so.3 (libc6) => /usr/lib/libcurl.so.3
So why cant g++ see it?
At link time, -lcurl tells the linker to look for libcurl.so.
From there, the SONAME within the library (libcurl.so.3) is embedded into the executable, and that's the filename that is searched for when executing.
You have libcurl.so.3 but may be lacking libcurl.so, which is needed for development.
What is your distribution? Usually there will be a second package with development headers/libraries, separate from the runtime bits.
Copy the file from any source /usr/lib/libcurl.so and place it in /usr/lib/, then try to compile. It will work out.