I successfully compile my first Shared Library with the ld commannd. It is located in the following path.
/home/user/code/lib/libMy-lib.so
Although when I try to use it in a project I get the following error
/usr/bin/ld: cannot find -lMy-lib
This it my compile line
g++ SuperProject.cpp -o SuperProject -L/home/user/code/lib -lMy-lib -I/home/user/code/includes
I've been following these two tutorial and can't find what I'm doing wrong.
http://peon-developments.blogspot.ca/2011/07/creating-and-using-c-shared-libraries.html
http://www.javahotchocolate.com/tutorials/so.html
Set the path:
LD_LIBRARY_PATH=/home/user/code/lib
Related
I'm trying to include the MQTT-C-Client-Library in a simple C++ project.
I have included the header file succesfully like this #include "MQTTClient.h". Compiling it in the linux terminal was printing this errors:
[xy#localhost mosquittoProject]$ sudo g++ *.cpp -o MQTTTest
/tmp/ccHn3s6m.o: In function `main':
mosquitto_test.cpp:(.text+0x11e): undefined reference to `MQTTClient_create'
mosquitto_test.cpp:(.text+0x13f): undefined reference to `MQTTClient_connect'
collect2: error: ld returned 1 exit status
I figured out that I need to link the library after some googling: Example MQTT Client Code not working C
Based on this question and answer I tried compiling it again like this:
sudo g++ -L/home/xy/Desktop/paho.mqtt.c/build/output/ *.cpp -l paho-mqtt3c -o MQTTTest
Which compiles fine but when running I get still an error.
Console commands and output:
[xy#localhost mosquittoProject]$ sudo g++ -L/home/xy/Desktop/paho.mqtt.c/build/output/ *.cpp -l paho-mqtt3c -o MQTTTest
[xy#localhost mosquittoProject]$ ./MQTTTest
./MQTTTest: error while loading shared libraries: libpaho-mqtt3c.so.1: cannot open shared object file: No such file or directory
I replaced the actual username by xy in this post.
What am I doing wrong here?
The problem looks like the library (libpaho-mqtt3c.so.1) is not on the library path.
It looks like you are linking against the build location of the library and have not installed it to the default system location (e.g. /usr/local/lib) by running sudo make install.
By default on Linux the runtime linker searches the locations listed in /etc/ld.so.conf and /etc/ld.so.conf.d. if you edit these remember to run sudo ldconfig to update the cache.
You can add the location of the library to the LD_LIBRARY_PATH environment variable e.g.:
$ LD_LIBRARY_PATH=/home/xy/Desktop/paho.mqtt.c/build/output/ ./MQTTTest
I'm trying to test out a new dev environment and I am having some problems referencing some of the required Qt libraries.
First I ran this:
$ g++ HelloWorld.C -o HelloWorld -I /usr/local/Trolltech/Qt-4.5.1/include/QtCore/ -I /usr/local/Trolltech/Qt-4.5.1/include/
and got this error:
/tmp/ccmsm4kZ.o: In function `QString::QString(char const*)':
HelloWorld.C:(.text._ZN7QStringC2EPKc[_ZN7QStringC5EPKc]+0x1d): undefined reference to `QString::fromAscii_helper(char const*, int)'
/tmp/ccmsm4kZ.o: In function `QString::~QString()':
HelloWorld.C:(.text._ZN7QStringD2Ev[_ZN7QStringD5Ev]+0x2d): undefined reference to `QString::free(QString::Data*)'
collect2: ld returned 1 exit status
So then I added reference to the QtCore library via:
$ g++ HelloWorld.C -o HelloWorld -I /usr/local/Trolltech/Qt-4.5.1/include/QtCore/ -I /usr/local/Trolltech/Qt-4.5.1/include/ -L /usr/local/Trolltech/Qt-4.5.1/lib -lQtCore
which removed the compile errors, however when I try to run the program I get this error:
./HelloWorld: error while loading shared libraries: libQtCore.so.4: cannot open shared object file: No such file or directory
I wasn't able to find a solution for this problem via google. Anyone have advice?
That error indicates that while the linker can find the library at compilation, it can't find it during runtime.
You should update your LD_LIBRARY_PATH to include that location like this:
In ~.bashrc probably somewhere near the bottom:
export LD_LIBRARY_PATH=$LD_LIBRARY_PATH:/usr/local/Trolltech/Qt-4.5.1/lib
Alternatively, if you want to make this persistent throughout your system (and have root access), you can make an entry in /etc/ld.so.conf.d (on RedHat, I'm not sure about the other distributions)
touch /etc/ld.so.conf.d/qt.conf
Add the path to this file, and then update your runtime via /sbin/ldconfig
I have written some code in Lib_file.h and Lib_file.cpp. I wish to convert this code to a static library. I am able to compile the code (using the command g++ -I <necessary include files> -o Lib_file.o Lib_file.cpp)to get Lib_file.o. I am also able to add it to an archive using the ar rvs Lib_file.a Lib_file.o command. Now when I try to use this library in some other code using the -L option, I get undefined reference errors. This errors point to the code in my Lib_file.o . So my question is how do I get the code in my Lib_file.cpp to link to the libraries that it uses.
I have tried the following options so far
I. After creating the Lib_file.o, I tried the following command
g++ -L<include path> -l<.a files> Lib_file.o . On executing this command, I get the following error
/usr/lib/../lib64/crt1.o: In function `_start':
init.c:(.text+0x20): undefined reference to `main'
collect2: ld returned 1 exit status
II. I tried to include all the necessary .a files in a new archive along with my Lib_file.o using the ar command. Still I get the undefined reference error when I try to use the Lib_file.a library with my application
Please help me out here
First of all, all libraries are normally named something like libxyz.a where xyz is the name of the library.
Secondly, you try to create a program using only the object file you used for the library, and also linking it with itself. This will of course not work, since the library have no main function which is needed for normal programs. You have to create another program, and link that one with the library.
Like
gcc myotherprogram.c -o myotherprogram -L/some/path -lxyz
As you can see in my command line above, I placed the library last on the command line. It's needed because the linker look for dependencies in kind of reversed order.
Edit: Linking your static library with other libraries: You don't. A static library is completely standalone, and if it needs other libraries itself to work then they have to be present on the command line when compiling the actual program.
For example, lets say that library xyz depends on the standard math library (i.e. the m library). You can't "link" with it when creating the xyz library as you don't actually link static libraries, you just put a collection of object files together in an archive (ar and the .a extension is for archive). When you build the actual application that needs the xyz library you also needs to link with whatever libraries that xyz needs:
gcc myotherprogram.c -o myotherprogram -L/some/path -lxyz -lm
I have a very basic C++ project in code blocks that makes use of glfw.so and two other libraries that are compiled to .so files from another project, libHorde3D.so and libHorde3DUtils.so. The latter are placed in the project root folder, while glfw is somewhere in my /usr/lib (I think).
I have added the project folder to the linker and compiler search paths in code blocks. I have added the libHorde3D.so and libHorde3DUtils.so as well as glfw.so to the Link Libraries in the Linker Settings tab. I thought that this would be enough based on the previous similar questions here on stackoverflow.
However when I press build:
ld cannot find -lHorde3D.so
ld cannot find -lHorde3DUtils.so
ld cannot find -lglfw.so
My system is Arch Linux 64 and I am using GCC.
I also tried bopying libHorde3D.so and libHorde3DUtils.so in /usr/lib and /usr/lib64 with no success.
P.S. All search paths are copied across the Debug and Release target.
Say, if the library name is libmylibrary.so, then linker option to link against that library would look like -lmylibrary. Note that lib prefix and .so suffix are not there — they are added automatically by the linker. In your case it seems like you specified the wrong name. Try removing .so from it, that should solve the problem.
Here is a simple demonstration of how to trigger the failure by making a similar mistake:
$ echo 'int main() { return 0; }' > test.c
$ gcc -o test ./test.c -lc
$ gcc -o test ./test.c -lc.so
/usr/bin/ld: cannot find -lc.so
collect2: ld returned 1 exit status
$
The first command succeeds and the second one (with incorrect library name) fails.
You must not pass ".so". The linker options are
-lHorde3D -lHorde3DUtils -lglfw
This way the linker will search for "libHorde3D.so" etc. in the library path(s).
I am have been attempting to get a C++ project setup using boost file system library using eclipse. I followed these directions to install boost on my system. The directions where pretty much
download
extract
run bootstrap.sh
run ./bjam architecture=combined
That seemed to go fine, no errors. I then fired up eclipse and created a new test project called test with a single file called test.cpp. The code in it is:
#include <stdio.h>
#include <boost/filesystem.hpp>
int main() {
boost::filesystem::path path("/Users/schoen"); // random pathname
bool result = boost::filesystem::is_directory(path);
printf("Path is a directory : %d\n", result);
return 0;
}
This is just something simple to make sure it is all set up correctly. Of course I tried to compile at this point and it failed. Did some googling and found this site. It said to add the boost library to the linker by going to project properties and adding "boost_filesystem". I tried this, and well it didn't work.
Can someone point me in the right direction or give me a hint to how to set up Boost in an Eclipse project?
I am new to C++ and Eclipse, and most my experience is in Java with Netbeans. So I am pretty lost at the moment.
UPDATE
I just wanted to update on what I have tried based on the answers given.
Based on Alex's suggestion I added boost_system and boost_filesystem to the linker list. I was still getting the same compiler errors.
Following the suggestion from rve I added the path to the boost libraries to the Library search path. When this did not work. I cleared out the linker list and tried it with just the library search path. This also did not work.
I then cleared the Library search path. I then manually edited the command on the linker window to be 'g++ -L/Users/jacobschoen/Library/boost_1_45_0/stage/lib -lboost -lboost_filesystem'. This also did not work.
In all of these I tried setting the path to boost to be '/Users/jacobschoen/Library/boost_1_45_0' and '/Users/jacobschoen/Library/boost_1_45_0/stage/lib'. Neither worked.
As requested the comiler error for the above code is:
**** Build of configuration Debug for project test ****
make all
Building file: ../src/test.cpp
Invoking: GCC C++ Compiler
g++ -O0 -g3 -Wall -c -fmessage-length=0 -MMD -MP -MF"src/test.d" -MT"src/test.d" -o"src/test.o" "../src/test.cpp"
../src/test.cpp:10:32: warning: boost/filesystem.hpp: No such file or directory
../src/test.cpp: In function 'int main()':
../src/test.cpp:13: error: 'boost' has not been declared
../src/test.cpp:13: error: expected `;' before 'path'
../src/test.cpp:14: error: 'boost' has not been declared
../src/test.cpp:14: error: 'path' was not declared in this scope
make: *** [src/test.o] Error 1
If any one has any further suggestions I am still trying.
Second Update
On a suggestion by rholmes I added an include library along with the linker list and library search path. So now the compile error is:
**** Build of configuration Debug for project test ****
make all
Building target: test
Invoking: MacOS X C++ Linker
g++ -L/Users/jacobschoen/Library/boost_1_45_0 -o "test" ./src/test.o -lboost_system -lboost_filesystem
ld: library not found for -lboost_system
collect2: ld returned 1 exit status
make: *** [test] Error 1
Any ideas?
Just wanted to be clear on what actually worked, since it was kinda pieced together from a few answers.
Download the boost files and extract them to where you want to put them.
In your terminal navigate to the directory and run ./bootstrap.sh
When that is done run ./bjam (this takes a while so go smoke and get a cup of coffee)
Open up your eclipse Project and go to Project > Properties > C/C++ Build > Settings
Click on MacOS X C++ Linker > Libraries.
You should see a split window with the top being for 'Libraries (-l)'. In this section add both boost_system and boost_filesystem. In the bottom section it should be for 'Library Search Path (-L)'. Here you want to put the path to the stage/lib directory inside where you extracted the boost download. It should look similar to below:
Click GCC C++ Compiler > Includes. This will be a single pane where it says 'Include Paths (-I)', well I think it is an I as he font is weird and could be a lower case l also. Anyway in that section add the path to where you put boost without the stage/lib part. It should look like below:
Everything should compile now with out a problem, and if you need to use any other boost libraries it should be just a matter of adding it to the linker section where boost_filesystem and boost_system are. Enjoy.
Not sure where you do this in Eclipse these days, but under the include paths for Eclipse should be the path to the main boost directory (/Users/jacobschoen/Library/boost_1_45_0?). The compiler line should have something like the following in it, I would think:
Invoking: GCC C++ Compiler
g++ -I/Users/jacobschoen/Library/boost_1_45_0 -O0 -g3 -Wall -c -fmessage-length=0 -MMD (etc..)
Update: Looking at my system, the linker path on yours might be more appropriately:
-I/Users/jacobschoen/Library/boost_1_45_0/stage/lib
Depending, of course, upon how you've installed and built boost -- this is with my most recent attempt with a full source build. Depending upon how you obtained boost, this may or may not be different. I recently redid the boost on my Mac for 64 bit and haven't had much time to try it yet....
Add boost_system to the linker list, together with boost_filesystem.
I had recently uninstalled the boost rpm and installed Boost like how you did. I had no problems running Boost programs in Eclipse. I didn't add any extra parameters. Just installed boost and ran Boost programs. It works fine.
Tried your program in the vi editor. Commented out everything in main
#include <cstdio>
#include <boost/filesystem.hpp>
int main() {
/*boost::filesystem::path path("/Users/schoen"); // random pathname
bool result = boost::filesystem::is_directory(path);
printf("Path is a directory : %d\n", result);*/
return 0;
}
and it still gave this error:
/tmp/cc7TAIYS.o: In function `__static_initialization_and_destruction_0(int, int)':
test.cpp:(.text+0x29): undefined reference to `boost::system::get_system_category()'
test.cpp:(.text+0x35): undefined reference to `boost::system::get_generic_category()'
test.cpp:(.text+0x41): undefined reference to `boost::system::get_generic_category()'
test.cpp:(.text+0x4d): undefined reference to `boost::system::get_generic_category()'
test.cpp:(.text+0x59): undefined reference to `boost::system::get_system_category()'
collect2: ld returned 1 exit status
I'm puzzled. Boost programs work on my system, but your program's header files itself are giving a problem. I doubt it's a problem with Eclipse. It has to be something else.
I just ran into something very similar to this using eclipse and CDT... It turns out, using ubuntu and apt-get, libboost_system installs as libboost_system.1.40.0 in /usr/lib
If you try to add it via the library tab in Helios it will complain because it is looking for *.so and *.s0.1.40.0 clearly doesn't match that. However after looking closely at what the linker was trying to doo, I just typed the raw string "boost_system" into the include path adder. This resulted in the linker doing a " -lboost_system" which is a format the linker knows how to deal with in resolving version dependency... If you instead put in the full path to the .so file, the linker will just complain because it tries to do a " -l/usr/lib/libboost_system.so.1.40.0" .
So take my advice and just type in the simple " boost_system" after doing an apt-get install.. It will make it all very easy.