Good afternoon!
I'm currently working on a final project to close my first semester of C++ (and also programming in general) and I was wondering how I can properly link the implementation, header, and main files. The purpose is to be able to run them as just those 3 files, instead of being dependent on running them through a .project file.
This is an example of the project I'm doing:
Cat.cpp
#include <iostream>
#include "Cat.h"
using namespace std;
void speak()
{
cout << "meow" << endl;
}
void jump()
{
cout << "meow?" << endl;
}
Cat.h
#ifndef CAT_H
#define CAT_H
void speak();
void jump();
#endif // CAT_H
CatMain.cpp
#include <iostream>
#include "Cat.h"
using namespace std;
int main()
{
speak();
jump();
return 0;
}
The issue here is that when I open these files individually (without opening the .project file), I get the "undefined reference to WinMain#16" on Cat.cpp and "undefined reference" errors to the speak() and jump() functions on CatMain.cpp. The reason this might be an issue is because chances are that my professor won't have Code::Blocks to run it the same way as I do, so he will have to be able to run these standalone files rather than run the .project file.
Is there something I can do to link them together so that they're not dependent on the .project file to run properly?
Any help would be greatly appreciated =)
To run this or any C++ program without an IDE, you only need a C++ compiler available on the command line. (You may have to set an environment variable to the path to the compiler to use it on the command line)
To compile and run the code one could run the following commands on the command-line. (assuming a compiler such as GCC or MinGW, which uses the command g++ to compile C++)
g++ -c Cat.cpp (produces an .o object file for the implementation of Cat.cpp and Cat.h)
g++ CatMain.cpp Cat.o (compiles the main function as an executable and links the Cat.o to it)
a (in windows cmd)
./a.out (on *nix systems)
Related
I have a program with 3 files, and when IrRun the program via Code Runner it keeps printing errors.The icon for the "Log.hpp" file is C, not C++. It doesnt matter if I rename it to Log.h or anything, it seems that I cant create a c++ header file in vscode.
The 3 files are:
main.cpp
#include <iostream>
#include "log.hpp"
using namespace std;
int main() {
InitLog();
Log("Hello World");
return 0;
}
log.cpp
#include "log.hpp"
#include <iostream>
void InitLog() {
Log("Initializing Log");
}
void Log(const char *message) {
std::cout << message << std::endl;
}
log.hpp
#pragma once
void InitLog();
void Log(const char *message);
The error mesages are:
main.cpp: In function 'int main()':
main.cpp:5:5: error: 'InitLog' was not declared in this scope
InitLog();
^~~~~~~
main.cpp:6:5: error: 'Log' was not declared in this scope
Log("Hello World");
Need help.
Are you using Windows? Which compiler? Do you have Microsoft Build Tools installed or even Visual Studio? Are you using gcc or clang?
You must start VS Code from a developer prompt: Open a developer prompt console, navigate to the folder where you code is. Then enter
code .
Visual Studo Code will then open with the environment set up. Then open a terminal inside VSCode using Control-` and try
cl /EHsc main.cpp log.cpp
And it will create main.exe. You can run it in the terminal and it will not close... Next time you open the project you can just open the folder in VS Code, since it would then already have the json config files created
VS Code is just an IDE. So compilers must be installed and also extensions. And some JSON files and tasks must be set up. It is sometimes simple, sometimes not so simple, I believe. But doing that you will then have a powerful editor and an unbelievably flexible environment, since you can for instance run and debug code in nodejs or C or C++ or anything and even in Linux without leaving the session on your casual Windows machine.
Your question is about a specific vscode plugin called Code Runner. It's not really related to vscode. The way how Code Runner is designed will never work for multiple C++ source files. It's not the right tool for the job.
Perhaps you'd better off with Microsofts CMake Tools package for vscode. It does require you to create your own CMakeLists.txt file though. In your case you'd need nothing more than:
add_executable(log
main.cpp
log.cpp
)
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.
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 have two files:
hello.h and hello.cpp
hello.h
#ifndef __HELLO_H__
#define __HELLO_H__
using namespace std;
void PrintMessage();
#endif
hello.cpp
#include <iostream>
#include "hello.h"
using namespace std;
void PrintMessage()
{
cout << "I want to be displayed!";
}
Now, I want to use PrintMessage() in a new .cpp file, but I keep getting an error message. This is what I'm doing:
printingmessage.cpp
#include <iostream>
#include "hello.h"
using namespace std;
int main()
{
PrintMessage();
return 0;
}
Am I just doing something blatantly wrong? I do have all of them in the same folder; I assume it has something to do with Dev-C++ (what I'm using to write/compile/run), but I can't figure it out. Anyone have any ideas?
I created a folder on my desktop, put all three files inside, and I tried to compile my printingmessage.cpp file exactly as it is. This is the error I'm getting:
[Linker error] Undefined reference to 'PrintMessage()'
i don't know dev C++ , but i would strongly advise if you do any serious coding to learn/move to the terminal and use make files, or a newer IDE such as visual studios.
heres a short script you can run save it as bash.sh
something like this
g++ hello.cpp -O2 -g -c
g++ hello.o printmessage.cpp -Wall -O2 -o print
then run it with ./print
I assume it has something to do with Dev-C++ (what I'm using to
write/compile/run), but I can't figure it out.
I guess so, too. Behind the scenes, the following things have to happen:
Both files get compiled. This creates a *.obj file for every *.cpp file, and uses the header.
The object files are linked against one another and possibly against required libraries.
Your problem lies in the “one another” part of the second step: the code compiles all right, but linking fails. The header file is irrelevant at that point. More precisely, the linker invocation for printingmessage.obj contains a reference to a function which isn't defined in that object file or any of the default libraries. Most likely the problem is due to the *.cpp files not being part of the same project. You need to create a multi-source-file project where you can link multiple object files. How you do that with Dev-C++ is probably somewhere in their manuals.