variable is being used without initialized

**Aeoskype** · 01-27-2015

I get an error when i try to compile this code. I tried to allocate memory in main function and that works. But why it doesn't work in function? I think that there is something wrong with function argument, but not sure.

Code:

#include <iostream>
#include <fstream>


using namespace std;


struct Word
{
    char letter[ 50 ];
};


void ReadFromFile( const char* filename, Word* dictionary, int& n )
{
    ifstream fin( filename );
    fin >> n;
    dictionary = new Word[ n ];
    for( int i=0; i<n; i++ )
    {
        fin >> dictionary[ i ].letter ;
    }
    fin.close();
}




int main()
{
    Word* dictionary;
    int n;


    ReadFromFile( "A.txt", dictionary, n );
    for( int i=0; i<n; i++ )
    {
        cout << dictionary[ i ].letter << endl;
    }


    return 0;
}

**laserlight** · 01-27-2015

The problem is that the dictionary parameter in ReadFromFile is a pointer to Word, so when you write:

Code:

dictionary = new Word[ n ];

what happens is that you're changing the value of this parameter, but this change is not reflected in the caller since pass by value is used. One approach is to use a reference parameter:

Code:

void ReadFromFile( const char* filename, Word*& dictionary, int& n )

That said, I note that you forgot to write a delete[] to match the new[]. You should consider using a container such as std::vector instead of doing manual memory management.

**Elysia** · 01-27-2015

I will also add that you should use std::string, and not char arrays. I will also note that your code is pretty fragile. Change the size of your array and problems may appear (again, use std::string).

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