I have written an SFML C++ game, and tried to start using threads, but after a while everything crashes. After searching I found out the fix seems to be to call XInitThreads();
but this does not work somehow.
simplified code:
#include <X11/Xlib.h>
int main() {
XInitThreads();
//other stuff
return 1337;
}
The error message I get when i try to compile is "undefined reference to symbol 'XInitThreads'. Could it be that the header file is working but there is no file where that method is implemented?
"undefined reference to symbol" is a linker error, not a compiler error. If you get this message, the compiler has already finished compiled the file into an object file, but is unable to find the shared library which contains the function to link the object file into an executable.
If you're using gcc, it generally means you have to add some -l flags, like so:
$ gcc prog.c -lX11
note that the order of -lX11 in the compiler argument matters, you would get an error if you do this:
$ gcc -lX11 prog.c
/tmp/ccBCxiFT.o: In function `main':
:(.text+0x5): undefined reference to `XInitThreads'
collect2: error: ld returned 1 exit status
You should add link X11 library setting -lX11 to your project. If you are using Eclipse navigate to projectproperties->C/C++ Build->Settings->Tool Settings->GCC Linker->Libraries and add "X11"
Add header-
#include<X11/Xlib.h>
Compile your source code using-
gcc <filename.extension> -lX11
Tested in Ubuntu 16.04 LTS
Related
I'm working on a C++ application. I would like to embed SpiderMonkey in the application.
I'm working with CMake, but I couldn't get that build. So, in an attempt to reduce complications, I tried the example code on this page. This wouldn't link using cmake or gcc from the command line.
So, even simpler, just to ensure I can link properly I am trying to get the following to work.
From the command line with gcc:
g++ --std=c++11
-I/home/thetasinner/moz/js/src/build_DBG.OBJ/dist/include
-L/home/thetasinner/moz/js/src/build_DBG.OBJ/js/src -DDEBUG
-Wl,--verbose -lmozjs-54a1 -lm -lz -ldl test.cpp -o test
On the following minimal code example:
#include <iostream>
#include <stdexcept>
#include "jsapi.h"
#include "js/Initialization.h"
int main(int argc, char** args) {
if (!JS_Init()) {
throw std::runtime_error("failed to initialise.");
}
std::cout << "It's alive!\n";
JS_ShutDown();
return 0;
}
Even this doesn't link. I get the errors
/tmp/ccqjx5RY.o: In function `main':
custom.cpp:(.text+0xf2): undefined reference to `JS_ShutDown()'
/tmp/ccqjx5RY.o: In function `JS_Init()':
custom.cpp:(.text._Z7JS_Initv[_Z7JS_Initv]+0xa): undefined reference to
'JS::detail::InitWithFailureDiagnostic(bool)'
collect2: error: ld returned 1 exit status
The headers are found and the linker is finding the mozjs library
attempt to open /home/thetasinner/moz/js/src/custom_build_DBG.OBJ/js/src
/libmozjs-54a1.so succeeded
-lmozjs-54a1 (/home/thetasinner/moz/js/src/custom_build_DBG.OBJ/js/src
/libmozjs-54a1.so)
I am working on Linux (Ubuntu 16.04 and Debian 8.7 tried) because that's where the build tools are. I don't even want to touch Window's yet.
The 'js' executable built in the spidermonkey build works fine, which I assume has the lib I'm trying to link inside it. So I would have thought the lib itself is built okay.
Can anybody help me resolve these linker errors? There are lots of answers to questions about much older versions of SpiderMonkey, but there's nothing for more recent versions. I'm interested in version 45 (which I've tried with very similar errors) or the tip version 52.
I'm comfortable enough digging around in the code working out how to do what I want with it once it builds, hence the interest in the latest version which isn't properly documented, I'm just completely stumped with the building step.
I suspect it's just an ordering problem on the command line:
g++ --std=c++11
-I/home/thetasinner/moz/js/src/build_DBG.OBJ/dist/include
-L/home/thetasinner/moz/js/src/build_DBG.OBJ/js/src -DDEBUG
test.cpp -o test
-Wl,--verbose -lmozjs-54a1 -lm -lz -ldl
Compilation first, followed by linking, with libraries in order of dependency. (My first guess was you'd neglected to mention mozjs on the command line. It took a second look to see it was just in the wrong place.)
Have a relatively new and fresh installation of ubuntu LTS, I followed the instructions found here for generic dynamic library building: http://www.bulletphysics.org/mediawiki-1.5.8/index.php/Installation
Installation appears to go smoothly (no errors or warnings) and afterwards I have all of the necessary files located in /usr/local/include/bullet. I'm currently attempting to compile a file from the following shell command:
g++ bulletTest.cpp -lGL -lGLU -I /usr/local/include/bullet/
bulletTest.cpp is:
#include <iostream>
#include <btBulletDynamicsCommon.h>
int main (void)
{
btBroadphaseInterface* broadphase;
return 0;
}
This file has nothing to it, but is throwing a plethora of undefined reference errors, such as "/tmp/ccH09wLR.o:(.rodata._ZTV17btTypedConstraint[_ZTV17btTypedConstraint]+0x30): undefined reference to `__cxa_pure_virtual'" I cannot find any other complaints on the forums/SO so I believe it must be a problem with my build/installation. These types of errors occur while attempting both gcc and g++ compilers.
Anybody have an idea?
EDIT: changed my shell command to g++ bulletTest.cpp -lGL -lGLU -lBulletDynamics -lBulletCollision -lBulletSoftBody -lLinearMath -I /usr/local/include/bullet/
It compiles but does not run, error is: error while loading shared libraries: libBulletDynamics.so.2.82: cannot open shared object file: No such file or directory
So it was a lot of little stuff. Firstly, don't reference "lbullet" reference each of the libraries needed:
g++ bulletTest.cpp -o bulletTest -lGL -lGLU -lBulletDynamics -lBulletCollision -lBulletSoftBody -lLinearMath -I /usr/local/include/bullet/
In addition, I had to set the LD_LIBRARY_PATH variable
export LD_LIBRARY_PATH=/usr/local/lib
and then it would both compile and run.
My OS is Windows 7 64-bit and C++ compiler I'm using is:
g++ (i686-posix-dwarf-rev0, Built by MinGW-W64 project) 5.3.0
And I installed Boost version 1.60 using:
bootstrap.bat mingw
b2 install target=gcc
Then I tested is it working, using examples from Boost.Random tutorial.
With the first two everything was fine, but the third one gave linker errors about boost::random::random_device. I minimized the code to have only this:
// Compiled with:
// g++ -IC:/Boost/include/boost-1_60
// -LC:/Boost/lib -lboost_random-mgw53-mt-1_60
// main.cpp
#include "boost/random/random_device.hpp"
int main() {
boost::random::random_device rng;
}
And I get the following errors:
C:\Users\Daniel\AppData\Local\Temp\cc5DfdjZ.o:main.cpp:(.text+0x15):
undefined reference to `boost::random::random_device::random_device()'
C:\Users\Daniel\AppData\Local\Temp\cc5DfdjZ.o:main.cpp:(.text+0x20):
undefined reference to `boost::random::random_device::~random_device()'
collect2.exe: error: ld returned 1 exit status
Here, on SO, I found that someone with similar problem added -lboost_system to flags, but for me it didn't helped.
Does anyone have any idea, why it isn't working? I checked, and I have random_device.hpp header in my Boost folder, with declarations of random_device() and ~random_device() in it.
I found what was wrong - the g++ command syntax, that I wanted to use to compile and link my code.
As I wrote in my question, I do this that way:
g++ -IC:/Boost/include/boost-1_60 -LC:/Boost/lib -lboost_random-mgw53-mt-1_60 main.cpp
While the correct one is with main.cpp (or any other source code file(s), that we want to include in compiling process) before the -L and -l flags.
For example:
g++ -IC:/Boost/include/boost-1_60 main.cpp -LC:/Boost/lib -lboost_random-mgw53-mt-1_60
or even
g++ main.cpp -IC:/Boost/include/boost-1_60 -LC:/Boost/lib -lboost_random-mgw53-mt-1_60
Hope it will help anyone, who will make such silly mistake too.
I'm trying access an extern device via a serial port and want to use Boost.Asio for this propose.
I have build the boost libraries for MinGw and compiled the regex example successful.
But I have problems to compile my code if I include something from Boost.Asio:
#include <boost/asio/serial_port.hpp>
int main() {
return 0;
}
g++ -D _WIN32_WINNT=0x0501 -O0 -g3 -Wall -c -fmessage-length=0 -osrc\SerialPortTest.o ..\src\SerialPortTest.cpp
g++ -LC:\boost-libs\boost\bin.v2\libs\thread\build\gcc-mingw-4.5.2\release\link-static\threading-multi -LC:\boost-libs\boost\bin.v2\libs\system\build\gcc-mingw-4.5.2\release\link-static\threading-multi -oSerialPortTest.exe src\SerialPortTest.o -lboost_thread-mgw45-mt-1_48 -lboost_system-mgw45-mt-1_48
src\SerialPortTest.o: In function `ZN5boost4asio6detail17winsock_init_base7startupERNS2_4dataEhh':
c:/mingw/bin/../lib/gcc/mingw32/4.5.2/../../../../include/boost/asio/detail/impl/winsock_init.ipp:39: undefined reference to `WSAStartup#8'
src\SerialPortTest.o: In function `ZN5boost4asio6detail17winsock_init_base7cleanupERNS2_4dataE':
c:/mingw/bin/../lib/gcc/mingw32/4.5.2/../../../../include/boost/asio/detail/impl/winsock_init.ipp:48: undefined reference to `WSACleanup#0'
collect2: ld returned 1 exit status
For me it seems to be a linking problem, but I don't get it.
Add -lws2_32 flag to link against WinSockets library.
Also, this might be useful: MinGW linker error: winsock
You miss wsock32 library. Add this to your dependencies and it should work.
I need to use libcurl in a piece of software I am writing on my ubuntu machine. I am using Eclipse to write and compile all of the software. When I put the libcurl files in the same folder as the .cpp file, and include the curl.h file in the header, When I attempt to compile the program, It comes up with these errors:
Building target: sms
Invoking: GCC C++ Linker
g++ -o"sms" ./src/sms.o
./src/sms.o: In function `main':
/home/geekman/workspace/sms/Debug/../src/sms.cpp:38: undefined reference to `curl_easy_init'
/home/geekman/workspace/sms/Debug/../src/sms.cpp:42: undefined reference to `curl_easy_setopt'
/home/geekman/workspace/sms/Debug/../src/sms.cpp:44: undefined reference to `curl_easy_setopt'
/home/geekman/workspace/sms/Debug/../src/sms.cpp:46: undefined reference to `curl_easy_perform'
/home/geekman/workspace/sms/Debug/../src/sms.cpp:47: undefined reference to `curl_easy_cleanup'
collect2: ld returned 1 exit status
make: *** [sms] Error 1
I took the contents of the include folder from libcurl, and placed them in the same folder as the .cpp file. then in the header of the .cpp file, I typed:
#include <curl/curl.h>
I also tried:
#include "curl/curl.h"
Any ideas on the problem? Thanks.
Your header file inclusions are just fine; your problem is occurring at the linking step. In order to link against libcurl, you need to add the -lcurl command line option, assuming it's installed in a standard directory:
g++ -o sms ./src/sms.o -lcurl
If it's not installed in a standard directory, you also need to add the -L/path/to/libcurl, e.g. something like:
# Assuming that /home/geekman/workspace/libcurl is where libcurl.a is located
g++ -o sms ./src/sms.o -L/home/geekman/workspace/libcurl -lcurl
Also note that the -lcurl option has to appear after the list of object files you're linking, otherwise it won't link properly.
You can try to use curl-config --libs.
An alternate answer (the first one is excellent). Consider using the output returned by "pkg-config --libs libcurl" as an argument to your compiler.
For example,
CPPFLAGS=`pkg-config --libs libcurl`
g++ $CPPFLAGS myfile.o
Pkg-config is a standard way for open source libraries to communicate to you how to link against them / #include their files.
Anyone who is using ecplise CDT then you need to do following. First on terminal enter
curl-config --libs
On my machine, the result is
-L/usr/lib/i386-linux-gnu -lcurl
then do according to this screenshot and you will be able to compile. btw don't forget to add header files in your code
So you enter library folder path without -L and library name without -l because they will be automatically added by linker.
You have to link the library to your program. With gcc (and most other compilers) you can specify the libraries to link with -lname_wo_lib, e.g. -lcurl
Also see GNU GCC Manual - Options for Linking for a detailed explanation of the options Adam Rosenfield said. For standard search directories, see An Introduction to GCC - for the GNU Compilers gcc and g++ - Setting Search Paths.
In addition to the first answer, I had to link the curlpp library too. So to compile the main.cpp file which included the curlpp I had to do:
g++ main.cpp -lcurl -lcurlpp
Using only one of the two links would return different errors regarding different links. It is important to remind that this only worked because I had installed all the necessary libraries in the standard include folders