C++ #include issue?

[Ryujin2003]

TL:DR; I'm not looking to have someone do my homework.

 

I'm not very experienced in C++. I'm doing a lab assignment for class. It "works" well enough, but I know that I'm including improperly. I feel that I should be able to include the header file and be fine; however, whenever I do that, I get the following error:

Quote

/home/nachos/code/build.linux/../threads/threadtest.cc:12: undefined reference to `Stack::Stack(int)'
/home/nachos/code/build.linux/../threads/threadtest.cc:18: undefined reference to `Stack::Push(int)'
/home/nachos/code/build.linux/../threads/threadtest.cc:19: undefined reference to `Stack::GetSize()'
/home/nachos/code/build.linux/../threads/threadtest.cc:31: undefined reference to `Stack::GetSize()'
/home/nachos/code/build.linux/../threads/threadtest.cc:35: undefined reference to `Stack::GetSize()'
/home/nachos/code/build.linux/../threads/threadtest.cc:36: undefined reference to `Stack::GetSize()'
/home/nachos/code/build.linux/../threads/threadtest.cc:37: undefined reference to `Stack::Pop()'
/home/nachos/code/build.linux/../threads/threadtest.cc:39: undefined reference to `Stack::GetSize()'
/home/nachos/code/build.linux/../threads/threadtest.cc:40: undefined reference to `Stack::GetSize()'
collect2: error: ld returned 1 exit status
Makefile:344: recipe for target 'nachos' failed
make: *** [nachos] Error 1

But, if I #include stack.cc, it compiles correctly and runs as expected. Can someone please educate me and tell me what I'm missing? I feel like it has to be something super small. I've modified the Makefile to include everything (these files are added to a pre-existing file). Any guidance would be great. Thanks in advance.

 

//stack.h

#ifndef STACK_H
#define STACK_H


class Stack {
public:
        Stack(int sz);
        // Constructor: initialize variables, allocate space.
        void Push(int value);
        // Push an integer, checking for overflow.
        void Pop();
        // Pop the top value of the stack
        bool Full();
        // Returns TRUE if the stack if full, FALSE otherwise.
        int GetSize();
        // Returns the size of the Stack
private:
        int size;
        // The maximum capacity of the stack.
        int top;
        // Index of the top of the stack.
        int *stack;
        // A pointer to an array that holds the contents.
};

#endif //STACK_H

#include "stack.h"
void Stack::Stack(int sz) {
    size = sz;
    top = 0;
    stack = new int[size];
// an array of integers of size "size"
}
bool Stack::Full() {
    return (top == size);
}
void Stack::Push(int value) {
    ASSERT(!Full());
        // ASSERT(!this->Full())
    stack[top++] = value;
        // this->stack[this->top++] = value
}

void Stack::Pop() {
//    if (top != 0) {
//        top = (top - 1);
//    }
    if (top > 0) {
        stack[top--];
    }
}

int Stack::GetSize() {
    return top;
}

And the test class it's being implemented in.

#include "kernel.h"
#include "main.h"
#include "thread.h"
#include "stack.h"

void
SimpleThread(int which)
{

    printf("Version 1");
    int num;
    Stack *s = new Stack(10);


    for (num = 0; num < 5; num++) {
        printf("*** thread %d looped %d times\n", which, num);
        printf("Hello World!\n");
        s->Push(num);
        printf("Size of the stack: %d \n", s->GetSize());

//        while( !s.empty() ) {
//             cout << s.top() << " ";
//        }

//        s->Pop();
        //printf("Stack size is: %d \n", s.size());

        kernel->currentThread->Yield();
    }

    printf("Size of the stack: %d \n", s->GetSize());

    printf("Emptying Stack:\n");

    while (s->GetSize() > 0) {
        printf("Items Remaining on Stack: %d \n", s->GetSize());
        s->Pop();
    }
    if (s->GetSize() == 0) {
        printf("Items Remaining on Stack: %d \n", s->GetSize());
        delete s;
    }
}

void
ThreadTest()
{
   // Stack *s = new Stack(5);
    Thread *t = new Thread("forked thread");
    t->Fork((VoidFunctionPtr) SimpleThread, (void *) 1);

    SimpleThread(0);
}

 

[2FA]

One thing I noticed is

void Stack::Stack(int sz){
    size = sz;
    top = 0;
    stack = new int[size];
// an array of integers of size "size"
}

in I assume stack.cpp. That void shouldn't be there as constructors don't have return types.

[Nutler]

In C++ compiling happens in compilation units.

Header files are used to publish types and function signatures that a compilation unit wants to have published and source files actually implement them. This is done so that a change in one compilation unit's implementation won't require one to recompile all the other ones as well (which might take even hours if a project is huge).

 

Taking real advantage of this requires using Make or some other build tool, so it's really not that important for smaller projects.

 

However, even in smaller projects doing includes the de facto way is clean, so:

1. Only include header files. This helps to keep compilation units clean (no fear of double definitions, etc.)

2. When compiling a smallish project without the help of a build system, compiling all compilation units every time is fine: 

gcc -o a.out stack.cc some_other_file.cc threadtest.cc

 

I assume the trouble (on the side of what 2FA pointed out) is that one of the source files is missing or there's some other problem with the Makefile. Like not compiling a compilation unit to an object file. So try to do it manually and see if that works.

Edited September 7, 2018 by Nutler
Noticed that Makefile is being used.....