It's been days searching for a way to get the MySQL C API working with a MinGW compiler, and frankly I have to say this is getting very frustrating.
I'm trying to compile the minimal example:
#include <my_global.h>
#include <mysql.h>
int main(int argc, char **argv)
{
printf("MySQL client version: %s\n", mysql_get_client_info());
exit(0);
}
and I keep on getting:
[Linker Error] undefined reference to `mysql_get_client_info#0'
I have compiled the libraries (including libmysql.a which contains mysql_get_client_info) and properly linked them, included all include and lib directories properly. Basiacly, everything is done by the letter according not only to the tutorials but also to forum posts which dealt specifically with this problem.
Now, what am I doing wrong?
Thanks
Having looked at your make-file, it would appear you've forgotten the mysql flags, required for your code to compile. On linux, you'd have to include the output of mysql_config --cflags --libs in the make file.
Add those to your makefile and the code should compile just fine.
Related
I am trying to switch to Windows environment from Linux, but find it a very hard path.
This time I wanted to test if I can work with boost library.
I had problems with compiling boost on windows, so I downloaded precompiled version. I unpacked everything and tested positively that I can compile the header-only librariers.
Then I copied some simple boost::asio example. I set up everything in Eclipse. Compilation went fine, but during linking I got 'undefined reference' problem to 'boost::system' internal stuff.
C:/Users/jacek/cpp/boost_1_62_0/boost/system/error_code.hpp:221: undefined reference to `boost::system::generic_category()'
C:/Users/jacek/cpp/boost_1_62_0/boost/system/error_code.hpp:222: undefined reference to `boost::system::generic_category()'
C:/Users/jacek/cpp/boost_1_62_0/boost/system/error_code.hpp:223: undefined reference to `boost::system::system_category()'
So I added '-lboost_system', as well as the path to the libraries directory, to my linking options. But this did not help.
g++ "-LC:\\Users\\jacek\\cpp\\boost_1_62_0\\lib64-msvc-14.0" -o TestAsio.exe "src\\Main.o" -lboost_system
I checked the libraries directory and found there is a bunch of files containing 'boost_system' in the name. They are:
libboost_system-vc140-mt-1_62.lib
libboost_system-vc140-mt-gd-1_62.lib
libboost_system-vc140-mt-s-1_62.lib
libboost_system-vc140-mt-sgd-1_62.lib
libboost_system-vc140-s-1_62.lib
libboost_system-vc140-sgd-1_62.lib
I did not know which I should use. I tried adding 'libboost_system-vc140-mt-1_62' to the linking options, I tried all other files, I tried renaming the files to the linux pattern 'libboost_system.a', but nothing worked.
g++ "-LC:\\Users\\jacek\\cpp\\boost_1_62_0\\lib64-msvc-14.0" -o TestAsio.exe "src\\Main.o" -llibboost_system-vc140-mt-1_62 -llibboost_system-vc140-mt-gd-1_62 -llibboost_system-vc140-mt-s-1_62 -llibboost_system-vc140-mt-sgd-1_62 -llibboost_system-vc140-s-1_62 -llibboost_system-vc140-sgd-1_62
What am I doing wrong here?
Please help...
YotKay
I solved it myself with the help of a comment from this post: boost asio example compilation error
It looks like the precompiled version of Boost is created with Visual Studion and is NOT COMPATIBLE with G++. I if I decided to install MinGW then I cannot use the precompiled version of boost, but must compile it myself using g++.
I did that.
Now I have libraries compiled with G++.
I specify the path to the boost system library like that:
c:\Users\jacek\cpp\boost_1_62_0\libraries\boost\bin.v2\libs\system\build\gcc-mingw-6.2.0\debug\link-static\
and add this option:
-lboost_system-mgw62-d-1_62
Now the problem with boost::system disappears. However, another one pops up with boost asio, but luckily the answer is here: MinGW linker error: winsock
The example works fine now on my Windows 10 laptop.
#include <boost/asio/io_service.hpp>
#include <boost/asio/steady_timer.hpp>
#include <chrono>
#include <iostream>
using namespace boost::asio;
int main()
{
io_service ioservice;
steady_timer timer{ioservice, std::chrono::seconds{3}};
timer.async_wait([](const boost::system::error_code &ec)
{ std::cout << "3 sec\n"; });
ioservice.run();
}
I am having trouble using the SDL framework in my xcode project, my main (all there is in the project at the moment) currently looks like this:
#include <SDL/SDL.h>
#include <iostream>
int main(int argc, const char * argv[])
{
// insert code here...
std::cout << "Hello, World!\n";
return 0;
}
And the error I am receiving when building is:
Undefined symbols for architecture x86_64:
"_main", referenced from:
start in crt1.10.6.o
(maybe you meant: __Z8SDL_mainiPPKc)
ld: symbol(s) not found for architecture x86_64
clang: error: linker command failed with exit code 1 (use -v to see invocation)
It does not give me an error about the framework not being found. and I have looked around Stackoverflow for this problem and I did find one person who had their framework in the wrong place on their OS. But I have tried all places (/library/frameworks && /~username~/library/frameworks && /system/library/frameworks) and still no luck.
Additional info:
I did however notice after some searching on the internet that the official website http://www.libsdl.org/download-1.2.php
Does not have a OSX version of the Development library. While many tutorials on how to use SDL on OSX say these are required.
Also I am adding my library via Xcode itself ,not through drag'ndrop. Xcode seems to reckognize it.
Would be much appreciated if anyone could help, going crazy over this error.
UPDATE:
Still no luck, I have followed every step provided by solutions here below. perhaps this screenshot is of any help.
The main() function is corrected, but didn't help. I tried changing the path to the header files, im lost on this one. Does anyone perhaps have any alternatives to building this in xcode?
UPDATE2:
The suggestion worked, however now it is giving me this warning, which won't let me run the application.
Fixed! I removed the path in the build settings. Strange how I still don't know what went wrong, either way. thanks a lot for the help! made my day!
I see three possible problems. The first problem is how you're including SDL.h in your code. You should include SDL.h with the following code:
#include "SDL.h"
The second possible problem is you haven't added the files SDLMain.h and SDLMain.m to your project. Those files are necessary to compile SDL code on Mac OS X. The files are in the devel-lite folder on the SDL disk image.
The third possible problem is that your project doesn't link to the Cocoa framework. The Mac version of SDL uses Cocoa so you need the Cocoa framework in your project.
The following article walks you through the setup of an Xcode 4 project for SDL:
Using SDL with Xcode 4
UPDATE
I noticed a possible problem in how you defined the main() function. You have a space between char and * and another space between * and argv, which could be causing the error. The main() function in my SDL code is defined in the following way:
int main(int argc, char *argv[])
I am new to using libraries and I am having some trouble with lapack++ and getting it to work. I will explain what I have done and tried so far.
First I installed BLAS and LAPACK and that went fine. I now have installed LAPACK++ version 2.5.2 (http://lapackpp.sourceforge.net/) so I can call various linear algebra routines in C/C++. After I configure, make and then make install it places all the C/C++ header files in /usr/local/include/lapackpp/ some of which are..
arch.h
bmd.h
gmf.h
lapackc.h
lautil.h
spdmd.h
ultgmd.h
bfd.h
...
and also the following files in /usr/local/lib
liblapackpp.la
liblapackpp.so
liblapackpp.so.14
liblapackpp.so.14.2.0
Now if I try to compile using g++ the simple code of
#include <lapackpp/lapackpp.h>
using namespace std;
int main(int argc, char** argv) {
return 0;
}
I get the following output...
In file included from /usr/local/include/lapackpp/lapackc.h:14,
from /usr/local/include/lapackpp/lapack.h:10,
from /usr/local/include/lapackpp/lapackpp.h:16,
from test.cpp:1:
/usr/local/include/lapackpp/lacomplex.h:45:23: error: laversion.h: No such file or directory
/usr/local/include/lapackpp/lacomplex.h:48:17: error: f2c.h: No such file or directory
In file included from /usr/local/include/lapackpp/lapackpp.h:47,
from test.cpp:1:
/usr/local/include/lapackpp/latmpl.h:36:22: error: lafnames.h: No such file or directory
I solved this problem by writing the location of the header file explicitly in the header file that was causing trouble.
Eg. I replaced
#include
with
#include
After doing this my code compiles fine.
Now if I try to compile the code
#include <cstdlib>
#include <iostream>
#include <lapackpp/lapackpp.h>
using namespace std;
int main(int argc, char** argv) {
LaGenMatDouble A(5,5);
cout << "This is a test." << endl;
return 0;
}
by typing
g++ test.cpp -o test -I usr/local/include/lapackpp
I get the following errors
/tmp/ccAq6nkP.o: In function `main':
test.cpp:(.text+0x22): undefined reference to `LaGenMatDouble::LaGenMatDouble(int, int)'
test.cpp:(.text+0x4f): undefined reference to `LaGenMatDouble::~LaGenMatDouble()'
test.cpp:(.text+0x67): undefined reference to `LaGenMatDouble::~LaGenMatDouble()'
collect2: ld returned 1 exit status
(Info on LaGenMatDouble is here )
which suggests I may be linking to the library wrong?
After some googling I realised that I needed to link to the header files using -I and the shared library by -L and the library itself by -llapackpp, so then I typed
g++ test.cpp -o test -I usr/local/include/lapackpp -L usr/local/lib -llapackpp
which compiled the code, now when I ran the program by typing ./test I go the error
./test: error while loading shared libraries: liblapackpp.so.14: cannot open shared object file: No such file or directory
and now I am confused.
I am unsure if this has anything to do with the problem but when I type
pkg-config lapackpp --libs
I get
Package lapackpp was not found in the pkg-config search path.
Perhaps you should add the directory containing `lapackpp.pc'
to the PKG_CONFIG_PATH environment variable
No package 'lapackpp' found
The same happens for lapack and blas too.
I am unsure what to do. Any help would be very much appreciated, thanks!
Linking goes fine because you tell to the linker where the library is, but execution failed because the loader doesn't know anything about the location of your libraries (you can check that performing ldd yourapp, which shows the library needed by your application).
Usually, you can solve that by telling to the loader where the library is through the variable LD_LIBRARY_PATH, but it is a crude tool. A different solution is to encode that instruction directly in the executable, as described here, or simply to link statically your application using the switch -static
If you're after a C++ library that wraps LAPACK (and/or BLAS), you might be better off using a more modern library such as Armadillo. Besides using LAPACK as a backend for solvers and matrix factorizations, it uses expression templates to speed up operations.
I'm not sure why this is, but 99% of the problems I have with programming in C++ have to do with the gcc linker.
I want to link the Qt library to a project in CodeLite. This is the code I have so far:
#include <QApplication>
int main(int argc, char *argv[])
{
return 0;
}
When I compile, I get the error
/Users/andrew/Dev/C++/COSC 102/elitecod/main.cpp:1:24: error: QApplication: No such file or directory
I have Qt installed (with Homebrew, Mac OS X Lion) in /usr/local/include. Why is this happening, and how can I fix this problem?
The error indicates it can't find the file QApplication. You need to add the Qt 'include' directory to the list of places the compiler should look for it and other header files.
A brief google seems to indicate you may have other problems with Qt, you might want to keep this link handy.
I've been trying to use MySQL and C++ together but can't seem to get started as I cannot seem to gain usage of the relevant libraries.
I am on Win7 using MinGW compiler and working in Netbeans.
I have the code:
#include <cstdlib>
#include <iostream>
#include <my_global.h>
#include <mysql.h>
using namespace std;
int main(int argc, char **argv)
{
cout << "MySQL client version: " << mysql_get_client_info();
}
But netbeans cannot find my_global.h or mysql.h.
In properties of the project I've linked to the library libmysql.dll.
Also present in the same directory is mysqlclient.lib but I can't find a way to link to that as the NetBeans linker doesn't seem to register that extension type.
Any help would be greatly appreciated.
C
---PROGRESS
I went into NetBeans' Properties->Build->C++ section and added the include directory of my MySQL installation in the 'Include Directories' section. This has solved the above issue of not finding my_global.h or mysql.h but now it cannot find crtdbg.h...
Actually had crtdbg.h in an old Visual Studio installation, moved it and all the other .h files there over to my MinGW includes folder. Seems to find the .hs now but fails with loads of errors, probably an issue with the Visual Studio .h files not being compatible with MinGW. Back to the drawing board.
Set the include directories, mate. It is under Tools->Options->C++->Code Assistance. Add the path where the my_global.h is.
See this forum post.
I'm not sure in Windows, but in Linux you can use the mysql_config tool to get the correct flags to compile a client application:
For compiling:
$ mysql_config --cflags
-I/usr/include/mysql -DBIG_JOINS=1 -fno-strict-aliasing -DUNIV_LINUX -DUNIV_LINUX
And for linking:
$ mysql_config --libs
-Wl,-Bsymbolic-functions -rdynamic -L/usr/lib/mysql -lmysqlclient
Now, if you are using MinGW, options should be similar, probably dropping the *_LINUX ones.
My bet is that you are simply missing the -I<path_to_include_dir> bit.