The Background
I have the following source code
#include <libubuntuone-1.0/u1-music-store.h>
#include <libsyncdaemon-1.0/libsyncdaemon/libsyncdaemon.h>
static void
get_credentials (U1MusicStore *music_store,
gchar **oauth_consumer_token,
gchar **oauth_consumer_secret,
gchar **oauth_token,
gchar **oauth_token_secret)
{
SyncdaemonCredentials *credentials;
*oauth_consumer_token = *oauth_consumer_secret = *oauth_token = *oauth_token_secret = NULL;
*oauth_consumer_token = g_strdup (syncdaemon_credentials_get_consumer_key (credentials));
*oauth_consumer_secret = g_strdup (syncdaemon_credentials_get_consumer_secret (credentials));
*oauth_token = g_strdup (syncdaemon_credentials_get_token (credentials));
*oauth_consumer_secret = g_strdup (syncdaemon_credentials_get_token_secret (credentials));
}
int main()
{
return 0;
}
and I am compiling it with the following makefile
main: main.o
g++ main.o -o main
main.o: main.cpp
g++ -c main.cpp `pkg-config --cflags --libs gtk+-2.0`
I need to include the pkg-config option since the u1-music-store.h header tried to included gtk/gtk.h, but the compiler isn't able to find it on it's own.
libsyncdaemon.h is a meta-header whose only purpose is to include a larger list of headers, which can be seen below
#include <libsyncdaemon-1.0/libsyncdaemon/syncdaemon-authentication.h>
#include <libsyncdaemon-1.0/libsyncdaemon/syncdaemon-config-interface.h>
#include <libsyncdaemon-1.0/libsyncdaemon/syncdaemon-credentials.h>
#include <libsyncdaemon-1.0/libsyncdaemon/syncdaemon-daemon.h>
#include <libsyncdaemon-1.0/libsyncdaemon/syncdaemon-events-interface.h>
#include <libsyncdaemon-1.0/libsyncdaemon/syncdaemon-file-info.h>
#include <libsyncdaemon-1.0/libsyncdaemon/syncdaemon-filesystem-interface.h>
#include <libsyncdaemon-1.0/libsyncdaemon/syncdaemon-folder-info.h>
#include <libsyncdaemon-1.0/libsyncdaemon/syncdaemon-folders-interface.h>
#include <libsyncdaemon-1.0/libsyncdaemon/syncdaemon-interface.h>
#include <libsyncdaemon-1.0/libsyncdaemon/syncdaemon-publicfiles-interface.h>
#include <libsyncdaemon-1.0/libsyncdaemon/syncdaemon-share-info.h>
#include <libsyncdaemon-1.0/libsyncdaemon/syncdaemon-status-info.h>
#include <libsyncdaemon-1.0/libsyncdaemon/syncdaemon-status-interface.h>
#include <libsyncdaemon-1.0/libsyncdaemon/syncdaemon-transfer-info.h>
My problem
Whenever I try to compile my code, I get the following error:
main.o: In function `get_credentials(_U1MusicStore*, char**, char**, char**, char**)':
main.cpp:(.text+0x34): undefined reference to `syncdaemon_credentials_get_consumer_key'
main.cpp:(.text+0x3c): undefined reference to `g_strdup'
main.cpp:(.text+0x4e): undefined reference to `syncdaemon_credentials_get_consumer_secret'
main.cpp:(.text+0x56): undefined reference to `g_strdup'
main.cpp:(.text+0x68): undefined reference to `syncdaemon_credentials_get_token'
main.cpp:(.text+0x70): undefined reference to `g_strdup'
main.cpp:(.text+0x82): undefined reference to `syncdaemon_credentials_get_token_secret'
main.cpp:(.text+0x8a): undefined reference to `g_strdup'
collect2: ld returned 1 exit status
make: *** [main] Error
Using grep, I've tracked down the four syncdaemon_credentials_get_* functions to syncdaemon-credentials.h, which I would expect the compiler to be able to find since it's listed in libsyncdaemon.h, but for some reason that's not happening. I'm assuming it's for the reason that u1-music-store.h was unable to find gtk/gtk.h that compelled me to use the pkg-config option in my makefile, but I'm having trouble understanding why this is even the case to begin with. If the file's #included, I would expect it to be included by the compiler.
Using grep again I was able to track down g_strdup to a number of headers, but I also discovered that when I replaced by makefile with the single command
g++ main.cpp -o main `pkg-config --cflags --libs gtk+-2.0`
I can eliminate the g_strdup warning, and I'm just left with the function errors.
My question
There are two things I'm looking to know here:
What should my makefile look like in order to solve my specific problem
What is the general solution to my problem? I'm guessing it's something to do with daisy-chaining #include directives together, and having to use pkg-config to fix that, but I'm not sure.
You need to link against libsyncdaemon.so. Get the appropriate arguments from pkg-config ... libsyncdaemon-1.0.
You need to link against libraries that export the required symbols. If there is a .pc file then you can use it to get the appropriate arguments.
"Unresolved external symbol" (MSVC) and "undefined reference to" (GCC) mean that the compiler found the declarations but the linker couldn't find the definitions.
This either means that you forgot to compile and/or link against a .cpp or that you forgot to link against an external library (.lib (Windows) / .a (Unix/Linux)) or object file (.o) which contains said definitions.
Related
I am trying to use google's cityhash hashing function. I am unable to link it to my c++ code. I have installed cityHash and it has generated libcityhash.la, etc files in my /usr/local/lib.
I am setting LD_LIB_LIBRARY=/usr/local/lib, but it doesn't seem to link to these files.
CODE:
#include <iostream>
#include <fstream>
#include <cstdlib>
int main()
{
std::ifstream file("dev/urandom");
char buff[4096];
file.read(buff, 4096);
const uint128 hashed = CityHash128(buff,4096);
file.close();
}
Compiling:
g++ -o city cityHash.cpp
Error:
/tmp/cctSoHTX.o: In function main:
cityHash.cpp:(.text+0x73): undefined reference to `CityHash128(char const*, unsigned long)'
collect2: error: ld returned 1 exit status
I include "city.h" and trying to compile it as follows:
g++ -I /usr/local/include/ -L/usr/local/lib -llibcityhash.a cityHash.cpp -o city
But i m still getting :undefined reference to `CityHash128(char const*, unsigned long)' –
Ok, it's the good old "order makes a difference". Instead of:
g++ -I /usr/local/include/ -L/usr/local/lib /usr/local/lib/libcityhash.a cityHash.cpp -o city
you should do:
g++ -I /usr/local/include/ -L/usr/local/lib cityHash.cpp -o city -lcityhash
(libraries and object files are processed in the order of appearance in the command line, and since none of the code so far has used anything from the library when you list it, nothing gets include from that library - then when you get to the actual code that does use it, you don't give the linker the library after it, so it can't find the symbol - note that this is dependant on the behaviour of the linker, so the same rules may not apply in for example a MS Visual Studio compiler/linker setup)
I'm attempting to get the Octave C++ code here to compile in g++ (Ubuntu/Linaro 4.6.4-1ubuntu1~12.04) 4.6.4).
This trimmed version of the above will compile in g++:
#include <iostream>
#include <octave/oct.h>
using namespace std;
int main() {
// Matrix L=Matrix(2,2);
return 0;
}
but if I unremark out the line Matrix L=Matrix(2,2); then compile with g++ temp.cpp it gives the error message:
/tmp/ccTa3Am5.o: In function `Array2<double>::~Array2()':
temp.cpp:(.text._ZN6Array2IdED2Ev[_ZN6Array2IdED5Ev]+0x1f): undefined reference to `Array<double>::~Array()'
/tmp/ccTa3Am5.o: In function `Array<double>::Array(dim_vector const&)':
temp.cpp:(.text._ZN5ArrayIdEC2ERK10dim_vector[_ZN5ArrayIdEC5ERK10dim_vector]+0x26): undefined reference to `Array<double>::get_size(dim_vector const&)'
/tmp/ccTa3Am5.o:(.rodata._ZTV5ArrayIdE[vtable for Array<double>]+0x10): undefined reference to `Array<double>::~Array()'
/tmp/ccTa3Am5.o:(.rodata._ZTV5ArrayIdE[vtable for Array<double>]+0x18): undefined reference to `Array<double>::~Array()'
collect2: ld returned 1 exit status
I'm unsure why. Perhaps I'm missing an #include, perhaps I don't have an appropriate file installed, perhaps I'm not linking to the appropriate library, or perhaps I'm misusing Octave in some way.
Question: Why is this failing to compile? How can I fix it?
It compiles fine if I use mkoctfile --link-stand-alone temp.cpp as indicated at the above site, however, I'd like to use g++ if possible, since I eventually want to be able to call Octave functions from another program I've written in C++.
As indicated in my comment a simple example can be found in this Howto. So in your case a simple way to achieve compilation will be creating a makefile as follows:
makefile:
all: temp
clean:
-rm temp.o temp
temp: temp.o
mkoctfile --link-stand-alone -o temp temp.o
temp.o: temp.cpp
g++ -c -I$(OCTAVE_INCLUDE)
-I$(OCTAVE_INCLUDE)octave -o temp.o temp.cpp
$(OCTAVE_INCLUDE) is an environment variable that should be set to your octave include path (e.g. /usr/include/octave-x.x.xx). Then you can simply compile and link your test application using the command make all.
You need to link to the octave library. If the library is octave.a:
g++ -loctave temp.cpp
Add the library directories to your link command:
your-local-path\octave-x.x.xx\lib\
your-local-path\octave-x.x.xx\lib\octave\x.x.xx\
mkoctfile -L"\your-path\octave-x.x.xx\lib" -L"\your-path\octave-x.x.x\lib\octave\x.x.xx" --link-stand-alone temp.cpp
For cxx11 linker errors:
Converting std::__cxx11::string to std::string
"If you get linker errors about undefined references to symbols that involve types in the std::__cxx11 namespace or the tag [abi:cxx11] then it probably indicates that you are trying to link together object files that were compiled with different values for the _GLIBCXX_USE_CXX11_ABI macro. This commonly happens when linking to a third-party library that was compiled with an older version of GCC."
Defining the following macro before including any standard library headers should fix your problem:
#define _GLIBCXX_USE_CXX11_ABI 0
I am trying to learn how to use the C++ Boost.Thread library. I have installed the Boost libraries on my Ubuntu 11.10 system. I am following the book "The Boost C++ Libraries" by Schaling - specifically example 6.1 on page 66. I am trying to compile the following code example:
#include <boost/thread.hpp>
#include <iostream>
void wait(int seconds)
{
boost::this_thread::sleep(boost::posix_time::seconds(seconds));
}
void thread()
{
for(int i = 0; i < 5; ++i)
{
wait(1);
std::cout << i << std::endl;
}
}
int main()
{
boost::thread t(thread);
t.join();
}
However, when I compile this with the following from the command line:
$ g++ example61.cpp -o example61 -I /usr/local/include
I get the following output:
/tmp/cc6bVu1F.o: In function `main':
example6.cpp:(.text+0x9d): undefined reference to `boost::thread::join()'
example6.cpp:(.text+0xae): undefined reference to `boost::thread::~thread()'
example6.cpp:(.text+0xc6): undefined reference to `boost::thread::~thread()'
/tmp/cc6bVu1F.o: In function `boost::detail::thread_data_base::thread_data_base()':
example6.cpp:(.text._ZN5boost6detail16thread_data_baseC2Ev[_ZN5boost6detail16thread_data_baseC5Ev]+0x24): undefined reference to `vtable for boost::detail::thread_data_base'
/tmp/cc6bVu1F.o: In function `void boost::this_thread::sleep<boost::posix_time::seconds>(boost::posix_time::seconds const&)':
example6.cpp:(.text._ZN5boost11this_thread5sleepINS_10posix_time7secondsEEEvRKT_[void boost::this_thread::sleep<boost::posix_time::seconds>(boost::posix_time::seconds const&)]+0x35): undefined reference to `boost::this_thread::sleep(boost::posix_time::ptime const&)'
/tmp/cc6bVu1F.o: In function `boost::thread::thread<void (*)()>(void (*)(), boost::disable_if<boost::is_convertible<void (*&)(), boost::detail::thread_move_t<void (*)()> >, boost::thread::dummy*>::type)':
example6.cpp:(.text._ZN5boost6threadC2IPFvvEEET_NS_10disable_ifINS_14is_convertibleIRS4_NS_6detail13thread_move_tIS4_EEEEPNS0_5dummyEE4typeE[_ZN5boost6threadC5IPFvvEEET_NS_10disable_ifINS_14is_convertibleIRS4_NS_6detail13thread_move_tIS4_EEEEPNS0_5dummyEE4typeE]+0x30): undefined reference to `boost::thread::start_thread()'
/tmp/cc6bVu1F.o: In function `boost::detail::thread_data<void (*)()>::~thread_data()':
example6.cpp:(.text._ZN5boost6detail11thread_dataIPFvvEED2Ev[_ZN5boost6detail11thread_dataIPFvvEED5Ev]+0x1f): undefined reference to `boost::detail::thread_data_base::~thread_data_base()'
/tmp/cc6bVu1F.o:(.rodata._ZTIN5boost6detail11thread_dataIPFvvEEE[typeinfo for boost::detail::thread_data<void (*)()>]+0x10): undefined reference to `typeinfo for boost::detail::thread_data_base'
collect2: ld returned 1 exit status
I don't know how to interpret this. Can anyone help? Thank you so much!
That is a linking error. It means your code is correct and you include the correct headers, but the compiler doesn't link against the boost threading library. To fix this, you need to compile like this:
g++ example61.cpp -o example61 -I /usr/local/include -lboost_thread
If you've installed the Boost threading library to a non-standard path, you must also add it to the search path:
g++ example61.cpp -o example61 -I /usr/local/include -lboost_thread -L/usr/local/lib
You need to link with the library. Some Boost libraries are implemented entirely in the header files and do not need a library. But others, like thread, are implemented partly in headers and partly in compiled library code.
I believe that you need to add -lboost_thread-mt to your compile command.
Boost thread are not a template only library. You need to add a -lboost_thread while linking /compiling.
Most of the libraries in boost are implemented in headers. They can simply be included like you have done. Boost thread on the other hand, is of such a nature that you need to depend on its compiled units, only the declaration of its function are readily available to you in the header. So the compiler, or more correctly the linker, which is responsible for linking your calls to the declared functions /classes need to know where to look for these symbols. By invoking the compiler with a -lboost_thread you tell it to link to the library (-l) boost thread.
Following your comments I share with you compilation string for pocketcpp compilation tool:
g++ -static -I"\boost" "$(FULL_CURRENT_PATH)" -L"\MinGW\lib" -lboost_thread -lboost_system -o "$(CURRENT_DIRECTORY)\$(NAME_PART).exe"
Good luck,
I commented above, but wanted to share the full command line here.
g++ -std=c++11 thread_example.cpp -lboost_thread -lboost_system
[I'm using thread_example.cpp as the source filename; please replace with your own]
I am trying to compile a simple ssl program (it was taken from the openssl book source code).
The program has the following files: common.h common.c client.c server.c
I have installed openssl 0.9.7 so I have the same version with the book.
I have downloaded the source and ./Configure, make, make test, make install in the home directory.
In the common.h there are the following includes:
#include <openssl/bio.h>
#include <openssl/err.h>
#include <openssl/rand.h>
#include <openssl/ssl.h>
#include <openssl/x509v3.h>
I run gcc -Wall common.c client.c -o client but I get the following errors:
common.c: In function ‘init_OpenSSL’:
common.c:12:5: warning: implicit declaration of function ‘THREAD_setup’
/tmp/ccvI3HX4.o: In function `handle_error':
common.c:(.text+0x3a): undefined reference to `ERR_print_errors_fp'
/tmp/ccvI3HX4.o: In function `init_OpenSSL':
common.c:(.text+0x51): undefined reference to `THREAD_setup'
common.c:(.text+0x5a): undefined reference to `SSL_library_init'
common.c:(.text+0x97): undefined reference to `SSL_load_error_strings'
/tmp/ccRA0Co9.o: In function `do_client_loop':
client.c:(.text+0x71): undefined reference to `BIO_write'
/tmp/ccRA0Co9.o: In function `main':
client.c:(.text+0xbb): undefined reference to `BIO_new_connect'
client.c:(.text+0x106): undefined reference to `BIO_ctrl'
client.c:(.text+0x18e): undefined reference to `BIO_free'
collect2: ld returned 1 exit status
Obviously it cannot link to the header files...
When I run as suggested in one forum gcc -Wall common.c client.c -o client -lcrypto -lssl I get
common.c: In function ‘init_OpenSSL’:
common.c:12:5: warning: implicit declaration of function ‘THREAD_setup’
/tmp/cc2gjx8W.o: In function `init_OpenSSL':
common.c:(.text+0x51): undefined reference to `THREAD_setup'
collect2: ld returned 1 exit status
But adding -lpthread won't help resolve the problem...
Any idea why this happens and how to solve it?
My guess is that lcrypto and lssl are installed by default in ubuntu and by doing -lcypto is telling the linker to look at the systems headers and not the openssl installation ones...
Any help or pointers is appreciated!
Thank you!
In some code versions of openssl book, the thread related functions are stored in reentrant.c, (in fact the declaration of TRHEAD_setup, in the version i've seen is there), so try with:
gcc -Wall common.c client.c reentrant.c -o client -lcrypto -lssl
So i'm writing a serial transmision program, and have just changed over to using C++, it been a while since I used C++
(I've been working with C recently, and before that java)
Now I need to use LibSerial,
(it seems much simpler to use than C's termios)
my code is:
//gen1.cpp
#include "string2num.h" // a custom header
#include <iostream>
#include <SerialStream.h>
using namespace LibSerial;
//using namespace std;
int main(int argc, char*argv[])
{
if (argc<2)
{
std::cout<<argv[0]<<"requires the device name eg \"dev/tty0\" as a parameter\nterminating.\n";
return 1;
}
SerialStream theSerialStream(argv[1]); //open the device
return 0;
}
When I compile the output:
g++ -Wall -o gen1 gen1.cpp string2num.o
/tmp/cchPBWgx.o: In function `main':
gen1.cpp:(.text+0x121): undefined reference to `LibSerial::SerialStream::SerialStream(std::basic_string<char, std::char_traits<char>, std::allocator<char> >, std::_Ios_Openmode)'
/tmp/cchPBWgx.o:(.rodata._ZTVN9LibSerial15SerialStreamBufE[vtable for LibSerial::SerialStreamBuf]+0x24): undefined reference to `LibSerial::SerialStreamBuf::showmanyc()'
/tmp/cchPBWgx.o:(.rodata._ZTVN9LibSerial15SerialStreamBufE[vtable for LibSerial::SerialStreamBuf]+0x28): undefined reference to `LibSerial::SerialStreamBuf::xsgetn(char*, int)'
/tmp/cchPBWgx.o:(.rodata._ZTVN9LibSerial15SerialStreamBufE[vtable for LibSerial::SerialStreamBuf]+0x2c): undefined reference to `LibSerial::SerialStreamBuf::underflow()'
/tmp/cchPBWgx.o:(.rodata._ZTVN9LibSerial15SerialStreamBufE[vtable for LibSerial::SerialStreamBuf]+0x34): undefined reference to `LibSerial::SerialStreamBuf::pbackfail(int)'
/tmp/cchPBWgx.o:(.rodata._ZTVN9LibSerial15SerialStreamBufE[vtable for LibSerial::SerialStreamBuf]+0x38): undefined reference to `LibSerial::SerialStreamBuf::xsputn(char const*, int)'
/tmp/cchPBWgx.o:(.rodata._ZTVN9LibSerial15SerialStreamBufE[vtable for LibSerial::SerialStreamBuf]+0x3c): undefined reference to `LibSerial::SerialStreamBuf::overflow(int)'
collect2: ld returned 1 exit status
make: *** [gen1] Error 1
This is the linker complaining that it cannot find the functions referenced by the libserial header file.
If I look on my Linux system to see how the shared library is called:
$ dpkg -L libserial0
...
/usr/lib/libserial.so.0.0.0
/usr/lib/libserial.so.0
On my system this implies I would add -lserial as a g++ option (aka link with libserial.so) this would turn your compilation command into
g++ -Wall -lserial -o gen1 gen1.cpp string2num.o
Including the header file is not enough - you also need to link with the library that implements SerialStream. Assuming it is a static library called serstream.a (it is almost certainly actually called something else):
g++ -Wall -o gen1 gen1.cpp string2num.o serstream.a
old thread, but i still use Libserial. here the completed answer
My working setup.
Ubuntu 18.04
g++ 7.3.0
1) Install package for libserial
apt install libserial-dev
2) check for your headers(.h) and .so files
dpkg -l libserial0
dpkg -l libserial-dev
the first command give you the directory of shared library and the second gives you the headers location.
3) Your code.
I have to change a little your code, first i delete the custom header and modifing the constuctor call to this.
SerialStream theSerialStream;
4) compile with g++
Here my compiling command
g++ -o test -I/usr/include test.cpp -L/usr/lib/x86_64-linux-gnu -lserial -lpthread
check for the -lpthread linking option, beacuse Libserial uses mutex.
In Ubuntu/Debian make sure you have to libserial-dev package installed and use the '-lserial' flag for gcc.