I've watched several tutorials on C++ header files and did EXACTLY what they were showing, but I can't really understand why I can't use a function from other .cpp file.
Main.cpp
#include <iostream>
#include "Header.h"
int main() {
std::cout << sum(2, 2);
return 0;
}
Header.cpp
#include "Header.h"
int sum(int a, int b) {
return (a + b);
}
Header.h
#pragma once
int sum(int a, int b);
Your program is working as can be seen here.
To get your program working on your machine follow these steps(assuming you're using g++ and Ubuntu:
Step 1: Create a binary/executable using the command:
g++ main.cpp Header.cpp -o myexecutable
Step 2: Test/Run your executable created in the last step using the command:
./myexecutable
Alternate Solution: A shortcut
Now if you're wondering that you've to type the name of every source file to make the executable, then you can take a sigh of relief because there is a shortcut as given below:
Assuming you have many source files(.cpp files) in your current directory and you want to compile them all without writing the names of all of them, then you can use the command:
g++ ./*.cpp -o myexecutable
The above command will create a binary/executable named myexecutable .
By including files, the preprocessor simply makes the included file part of the file which includes the other file.
In C++, there is the one definition rule. If you include a definition multiple times in other files, you brake that rule. Simply that.
In general, the preprocessor nor the compiler has an idea what a '.h' or a '.cpp' file is, that is only a convention. But you must not have the same definition multiple times in your source files, independent if you link multiple objects or have the definition multiple times in one source file.
If you follow the convention, that you name your definition files with '.cpp', it makes no sense to include them in other files as this will end up in multiple definitions. Once in the object file generated from the '.cpp' file and once in the file which include the '*.cpp' file.
You can include the '.cpp' file once in another object file and use it, if you don't link the object file, which will be generated from that '.cpp' file. But is is a strongly advice to not do such strange things :-)
Header.cppfor you. Some workarounds are listed here: stackoverflow.com/questions/51720769/…, maybe that will help?tasks.jsonto build all files in the folder instead: https://code.visualstudio.com/docs/cpp/config-mingw#_modifying-tasksjson