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I'm trying to compile my project and getting multiple definition of function error:

CMakeFiles/OasisTest.dir/Tests/Oasis_test.cpp.o: In function `MinHeap::left(int)': /home/d_/CODING/CLionProjects/DS1-Course_Wet2/Oasis-2/Tests/../DataStructures/MinHeap.h:56: multiple definition of `MinHeap::MinHeap(int)' CMakeFiles/OasisTest.dir/Oasis.cpp.o:/home/d_/CODING/CLionProjects/DS1-Course_Wet2/Oasis-2/DataStructures/MinHeap.h:56: first defined here

It seems that I have variable definitions in my header file, and those should be removed or made extern, or made inline, but I don't have an idea what to change.

NOTE: I succeeding to compile without MinHeap.h

What I'm trying to compile as in CMakeLists.txt:

add_executable(OasisTest Oasis.cpp Tests/Oasis_test.cpp )

MinHeap.h

#ifndef OASIS_MINHEAP_H #define OASIS_MINHEAP_H #include <iostream> #include <climits> using namespace std; // Prototype of a utility function to swap two integers void swap(int* x, int* y); // A class for Min Heap class MinHeap { int* harr; // pointer to array of elements in heap int capacity; // maximum possible size of min heap int heap_size; // Current number of elements in min heap public: // Constructor MinHeap(int cap); // to heapify a subtree with the root at given index void MinHeapify(int); int parent(int i) { return (i - 1) / 2; } // to get index of left child of node at index i int left(int i) { return (2 * i + 1); } // to get index of right child of node at index i int right(int i) { return (2 * i + 2); } // to extract the root which is the minimum element int extractMin(); // Decreases key value of key at index i to new_val void decreaseKey(int i, int new_val); // Returns the minimum key (key at root) from min heap int getMin() { return harr[0]; } // Deletes a key stored at index i void deleteKey(int i); // Inserts a new key 'k' void insert(int k); bool isEmpty(); }; // Constructor: Builds a heap from a given array a[] of given size MinHeap::MinHeap(int cap) { heap_size = 0; capacity = cap; harr = new int[cap]; } // Inserts a new key 'k' void MinHeap::insert(int k) { if (heap_size == capacity) { cout << "\nOverflow: Could not insert\n"; return; } // First insert the new key at the end heap_size++; int i = heap_size - 1; harr[i] = k; // Fix the min heap property if it is violated while (i != 0 && harr[parent(i)] > harr[i]) { swap(&harr[i], &harr[parent(i)]); i = parent(i); } } // Decreases value of key at index 'i' to new_val. It is assumed that // new_val is smaller than harr[i]. void MinHeap::decreaseKey(int i, int new_val) { harr[i] = new_val; while (i != 0 && harr[parent(i)] > harr[i]) { swap(&harr[i], &harr[parent(i)]); i = parent(i); } } // Method to remove minimum element (or root) from min heap int MinHeap::extractMin() { if (heap_size <= 0) return INT_MAX; if (heap_size == 1) { heap_size--; return harr[0]; } // Store the minimum value, and remove it from heap int root = harr[0]; harr[0] = harr[heap_size - 1]; heap_size--; MinHeapify(0); return root; } // This function deletes key at index i. It first reduced value to minus // infinite, then calls extractMin() void MinHeap::deleteKey(int i) { decreaseKey(i, INT_MIN); extractMin(); } // A recursive method to heapify a subtree with the root at given index // This method assumes that the subtrees are already heapified void MinHeap::MinHeapify(int i) { int l = left(i); int r = right(i); int smallest = i; if (l < heap_size && harr[l] < harr[i]) smallest = l; if (r < heap_size && harr[r] < harr[smallest]) smallest = r; if (smallest != i) { swap(&harr[i], &harr[smallest]); MinHeapify(smallest); } } bool MinHeap::isEmpty() { return heap_size <= 0; } // A utility function to swap two elements void swap(int* x, int* y) { int temp = *x; *x = *y; *y = temp; } #endif //OASIS_MINHEAP_H

includes from Oasis.h

#include "library2.h" //Only typedefs #include "DataStructures/HashTable.h" //Includes AVLTree.h #include "DataStructures/AVLRankTree.h" //Include to AvlExceptions #include "DataStructures/MinHeap.h"

Oasis.cpp

#include "Oasis.h"

Oasis_test.cpp

#include "TestMacros.h" #include "../Oasis.h"

The full error:

CMakeFiles/OasisTest.dir/Tests/Oasis_test.cpp.o: In function `MinHeap::left(int)': /home/d_/CODING/CLionProjects/DS1-Course_Wet2/Oasis-2/Tests/../DataStructures/MinHeap.h:56: multiple definition of `MinHeap::MinHeap(int)' CMakeFiles/OasisTest.dir/Oasis.cpp.o:/home/d_/CODING/CLionProjects/DS1-Course_Wet2/Oasis-2/DataStructures/MinHeap.h:56: first defined here CMakeFiles/OasisTest.dir/Tests/Oasis_test.cpp.o: In function `MinHeap::left(int)': /home/d_/CODING/CLionProjects/DS1-Course_Wet2/Oasis-2/Tests/../DataStructures/MinHeap.h:56: multiple definition of `MinHeap::MinHeap(int)' CMakeFiles/OasisTest.dir/Oasis.cpp.o:/home/d_/CODING/CLionProjects/DS1-Course_Wet2/Oasis-2/DataStructures/MinHeap.h:56: first defined here CMakeFiles/OasisTest.dir/Tests/Oasis_test.cpp.o: In function `HashTable<int>::destroy_hash()': /home/d_/CODING/CLionProjects/DS1-Course_Wet2/Oasis-2/Tests/../DataStructures/MinHeap.h:63: multiple definition of `MinHeap::insert(int)' CMakeFiles/OasisTest.dir/Oasis.cpp.o:/home/d_/CODING/CLionProjects/DS1-Course_Wet2/Oasis-2/DataStructures/MinHeap.h:63: first defined here CMakeFiles/OasisTest.dir/Tests/Oasis_test.cpp.o: In function `swap(int*, int*)': /home/d_/CODING/CLionProjects/DS1-Course_Wet2/Oasis-2/Tests/../DataStructures/MinHeap.h:137: multiple definition of `swap(int*, int*)' CMakeFiles/OasisTest.dir/Oasis.cpp.o:/home/d_/CODING/CLionProjects/DS1-Course_Wet2/Oasis-2/DataStructures/MinHeap.h:137: first defined here CMakeFiles/OasisTest.dir/Tests/Oasis_test.cpp.o: In function `MinHeap::decreaseKey(int, int)': /home/d_/CODING/CLionProjects/DS1-Course_Wet2/Oasis-2/Tests/../DataStructures/MinHeap.h:83: multiple definition of `MinHeap::decreaseKey(int, int)' CMakeFiles/OasisTest.dir/Oasis.cpp.o:/home/d_/CODING/CLionProjects/DS1-Course_Wet2/Oasis-2/DataStructures/MinHeap.h:83: first defined here CMakeFiles/OasisTest.dir/Tests/Oasis_test.cpp.o: In function `MinHeap::extractMin()': /home/d_/CODING/CLionProjects/DS1-Course_Wet2/Oasis-2/Tests/../DataStructures/MinHeap.h:92: multiple definition of `MinHeap::extractMin()' CMakeFiles/OasisTest.dir/Oasis.cpp.o:/home/d_/CODING/CLionProjects/DS1-Course_Wet2/Oasis-2/DataStructures/MinHeap.h:92: first defined here CMakeFiles/OasisTest.dir/Tests/Oasis_test.cpp.o: In function `MinHeap::MinHeapify(int)': /home/d_/CODING/CLionProjects/DS1-Course_Wet2/Oasis-2/Tests/../DataStructures/MinHeap.h:118: multiple definition of `MinHeap::MinHeapify(int)' CMakeFiles/OasisTest.dir/Oasis.cpp.o:/home/d_/CODING/CLionProjects/DS1-Course_Wet2/Oasis-2/DataStructures/MinHeap.h:118: first defined here CMakeFiles/OasisTest.dir/Tests/Oasis_test.cpp.o: In function `MinHeap::deleteKey(int)': /home/d_/CODING/CLionProjects/DS1-Course_Wet2/Oasis-2/Tests/../DataStructures/MinHeap.h:111: multiple definition of `MinHeap::deleteKey(int)' CMakeFiles/OasisTest.dir/Oasis.cpp.o:/home/d_/CODING/CLionProjects/DS1-Course_Wet2/Oasis-2/DataStructures/MinHeap.h:111: first defined here CMakeFiles/OasisTest.dir/Tests/Oasis_test.cpp.o: In function `MinHeap::isEmpty()': /home/d_/CODING/CLionProjects/DS1-Course_Wet2/Oasis-2/Tests/../DataStructures/MinHeap.h:132: multiple definition of `MinHeap::isEmpty()' CMakeFiles/OasisTest.dir/Oasis.cpp.o:/home/d_/CODING/CLionProjects/DS1-Course_Wet2/Oasis-2/DataStructures/MinHeap.h:132: first defined here
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    Move every implementation of MinHeap member functions in a .cpp file or make them inline. Commented Jun 11, 2018 at 14:15
  • Have you tried one of the following: - move the declarations out of the header into a *.cpp file, or - removing the definitions and moving the declarations up to be in the correct visibility, i.e. MinHeap::MinHeap(...) becomes just MinHeap(...) under public:, inlined or header only. Commented Jun 11, 2018 at 14:17
  • @O'Neil Thanks I moved all members to .cpp file Commented Jun 11, 2018 at 14:44

1 Answer 1

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You are defining each member in the header file itself; so each time you include the header file in your source code, these members are redefined; that is why you are getting multiple definition error. To resolve this either define each member function in the class itself or move the definitions from header file to a separate cpp file(like other people suggested) and add that cpp file to add_executable command.

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3 Comments

...or mark the member functions as inline (which happens automatically when you define the functions inside the class definition).
What is so special about current MinHeap.h implementation, on my other DS I done the same thing, implement members in the same file
To resolve this either define each member function in the class itself, it answered my question thanks

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