I'm relatively new to coding in C++ and have started working with main and header files and I've created a program to test it out, however, the following program results in the following compiler error:
Undefined symbols for architecture x86_64:
"Print()", referenced from:
_main in test-7d0225.o
ld: symbol(s) not found for architecture x86_64
clang: error: linker command failed with exit code 1 (use -v to see invocation)
This is my current code.
test.cpp
#include <iostream>
#include "test.h"
using namespace std;
int main() {
Print();
return 0;
}
test.h
#ifndef TEST_H
#define TEST_H
void Print();
#endif
test1.cpp
#include <iostream>
#include "test.h"
using namespace std;
void Print() {
cout << "Hello" << endl;
}
Nothing I've found online has helped me and my only assumptions are that my compiler isn't set up correctly. I've tried compiling both of these of files by typing in "g++ test.cpp test1.cpp", as well, but yields similar results. I would like to note that I am on Mac as well. Please feel free to leave any comments or suggestions for how I've asked this question, this is my first time on stack overflow.
Your code seems just fine, I’ll will try to compile it on vscode myself.
One problem could be your vscode launch.json. I have had the same problem as what I am describing. Vscode can be quite “Finicky” with low level languages like c and c++. In your launch file (or tasks file if it calls something in tasks) make sure you compile *.cpp files in the folder. I would look something like {folder}/**.cpp. To find the exact command look on vscode’s official site.
Given that you tried compiling your code outside of vscode and assuming that everything is in the same folder, it might be a coding problem. Again, your code looks fine. Go online and find some learning to code website with multiple file coding. Copy their code and do the same thing that you did with your code. If it doesn’t work there is definitely a problem with how to code is being compiled. Otherwise revise your code and compare to find the problem.
Also, could you provide the terminal command vscode prints (I am also on Mac). It will be in the terminal tab in the g++ section, not in bash)
P.S. I am also new to stack overflow so any suggestions you have for me will be great.
Related
I am trying to write a C++ class in a separate header and cpp file using VS Code as my IDE with the 'run' and 'C++' extensions.
main.cpp
#include "Fan.h"
int main() {
Fan fan1;
return 0;
}
Fan.h
#ifndef FAN_H
#define FAN_H
class Fan {
public:
Fan();
};
#endif
Fan.cpp
#include "Fan.h"
#include <iostream>
using namespace std;
Fan::Fan() {
cout << "Fan Class" << endl;
}
I really can't seem to find anything popping out as obviously wrong. I am wondering if it is a setup problem with VS Code.
If I change #include "Fan.h" in main.cpp to "Fan.cpp" it works so it makes me think that the code works but that the linker is not setup right.
Would appreciate any help!
EDIT: Ok so I've tried the code in a different IDE and it worked. It's something to do with VS Code. Here is the error:
[Running] cd "c:\Users\<USER>\Desktop\Fan\" && g++ tempCodeRunnerFile.cpp -o tempCodeRunnerFile && "c:\Users\<USER>\Desktop\Fan\"tempCodeRunnerFile
C:\Users\<USER>\AppData\Local\Temp\cclMFKxO.o:tempCodeRunnerFile.cpp:(.text+0x57): undefined reference to `Fan::Fan()'
collect2.exe: error: ld returned 1 exit status
It sounds like the IDE is only compiling main.cpp. You need to find the command that is compiling main.cpp and ensure that it also compiles fan.cpp into fan.obj. You will also need to ensure that both main.obj and fan.obj are passed to the linker (which produces the executable program, main.exe or whatever).
There are two steps involved here:
cpp -> obj (compiling each source file into a matching object file)
obj -> exe (linking many object files into an executable)
I would say to make a CMakeLists.txt file and add main.cpp and fan.cpp into the add_executable section. Then VS can handle and run files through CMake.
I am just learning c++ and began to watch a youtube tutorial by thenewboston. Unfortunately he is using Code::Blocks while I am using gcc and I do not have the option to create new class files with a button click and so had to manually create them.
I dont understand why the same code in Code::Blocks and gcc will work in Code::Blocks but not gcc. Does gcc require different coding for the same language?
EDIT: I have downloaded and tested in Code::Blocks myself
Other questions talk of how I need to give windows an entry point, but I dont know how to do that.
Test.cpp Code:
#include <iostream>
#include "ClassTest.h"
using namespace std;
int main() {
ClassTest bo;
}
ClassTest.h Code:
#ifndef CLASSTEST_H
#define CLASSTEST_H
class ClassTest {
public:
ClassTest();
};
#endif // CLASSTEST_H
ClassTest.cpp Code:
#include <iostream>
#include "ClassTest.h"
using namespace std;
ClassTest::ClassTest() {
cout << "blah blah" << endl;
}
I'm not quite sure I understand what the question is; I'm going to take it as "how do I get these three files to build into a .exe that I can run from the Windows commmand line?"
The answer is to run something like this on the command line, in the folder with the files:
g++ -c Test.cpp -o Test.o
g++ -c ClassTest.cpp -o ClassTest.o
g++ Test.o ClassTest.o -o Test.exe
The first two commands build each CPP file into an "object file", which isn't a whole program by itself but which contains the compiled version of the code in that CPP file. The last command tells the compiler to paste together the two object files into a program, and resolve all the cross-references between them. (For example, the part where Test.cpp constructs a ClassTest object needs to end up calling the ClassTest constructor code from ClassTest.cpp.)
Code::Blocks is an IDE and works out how to build each source file in your project and link them together by itself. But if you aren't using an IDE, you need to do that in another way. You can either do it manually like this, or you can write a Makefile that will check which code files have changed and rebuild and re-link everything that depends on them when you run the make command, which is how most people do it.
As for "giving Windows an entry point", that probably refers to GUI applications that want to display windows on the screen. For console programs like the one you have written, the "entry point" is main(), and you just print stuff to the command line window. To make actual Windows-style GUI windows of your own, you need to use the Windows API, which I can't tell you much about.
this will probably a dumb question for you guy's but I have no experience in C++ what so ever. I'm using an open source project osrm (which is awesome). Still to request a route, you have make an http request. To reduce the running time, I would like to build a wrapper around the code and call it using the command line. So I googled a bit and found that osrm already creates a static lib (.a file) when compiling the project. I also found a piece of code that points me in the right directions for building a wrapper. So to begin I build a simple hello world program (see below) that includes some files from that static lib. To compile I followed this tutorial.
My directory structure looks like this:
./helloWorld.cpp
./libs/libOSRM.a
And the command to compile is this:
gcc –static helloworld.cpp –L ./libs –l libOSRM.a
The code it selve:
#include "Router.h"
#include "boost/filesystem/path.hpp"
#include "ServerPaths.h"
#include "ProgramOptions.h"
#include <InternalDataFacade.h>
#include <viaroute.hpp>
#include <iostream.h>
main()
{
cout << "Hello World!";
return 0;
}
the exact error I got:
fatal error: ServerPaths.h: No such file or directory #include "ServerPaths.h"
Add the -IPathToTheHeaderFiles to the compiler options. So it will find the files to be included. Replace PathToTheHeaderFiles with the path where your file ServPaths.h resides.
Edit: Add as many -I as you need for further header files.
Additionally it would be worth to read a book about C++ or/and the GCC manual1
1 Section 3.11 will help.
main.cpp
#include <iostream>
#include <string>
using namespace std;
void echo(string);
int main()
{
echo("hello");
cout << "Hello world!" << endl;
return 0;
}
print.cpp
#include <iostream>
#include <string>
void echo(string code){
cout << code;
}
After compiling the code in code blocks 12.11, it gives me that error:
undefined reference to `echo(std::string)
I use windows 7 x64.
I have added the directory; Project>build options > search directories and added the current working directory.
All the files are in one console project in code blocks
I believe you should read up a bit more on namespaces usage. You are missing std in print.cpp.
Generally, while starting to learn cpp or getting a grip of the language you should always try writing full names of the classes along with the namespaces. Eventually with practice and some oversights (like now) you will learn why you really need them. In a nutshell namespaces are great:
When you are writing code over multiple files
Compartmentalize your code into separate blocks.
Also, using namespace std; should be used within cpp files mostly (otherwise headers get mangled up.
Anyways, try changing your code to this:
#include <iostream>
#include <string>
void echo(std::string code){
std::cout << code;
}
Then your results will look like this:
> g++ main.cpp print.cpp -o a.out
> ./a.out
helloHello world!
You should get more than that linker error, since you use string without any namespace in your print.cpp file. And if that source file doesn't compile it can't be linked with, and you will get the linker error you have.
Change to e.g.
void echo(std::string code) { ... }
And you do try to link with the object file created from print.cpp ?
I know this is old, but for anyone looking to solve this issue, the following may be a solution for you. If you have g++ follow c++ 11 under project->build options (check your options anyway) then you must check that box for all files you make in the project for the error to be cleared up. I had that annoying undefined reference thing too but now it is gone!
Try "Project/Properties/Build Targets tab". There you should find "Build target files" field. In that filed find "print.cpp" and click the checkbox (now the compiler will build print.cpp).
Some usefull information on Project management in CB
http://www.codeblocks.org/docs/main_codeblocks_en.html
When dealing with strings in C++ its best to sue std::string and your code seems to be wrong with a changes like using std::cout instead of plain cout another thing you need to be careful is linking your files especially files in different directories you need to tell code blocks were to find this print.cpp by going to build option and go for the search tab directory and point to where print.cpp is other wise the other approach is to just build a project which will have the main.cpp and and then add print.cpp class to current project I hope this will be of some help
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[])