CODEWITHSUNDEEP
c++classdefinitionconstructctor-initializer
Yassine Mrabet
Yassine Mrabet

Reputation: 55

Problem while initializing attribute in constructor c++

While i try to debug ERROR appear : "Unhandled exception at 0x5784F2F6 (ucrtbased.dll) in Final project.exe: An invalid parameter was passed to a function that considers invalid parameters fatal." Tried every thing can't figure out how to solve this.

using namespace std;
class Map :
{
private:
    double *mhours_played;
    string *maps;
    unsigned element_num;
public:
    Map() 
    {
         maps[2] = { "Summoner's rift", "Aram" };
         element_num = 2; mhours_played[2] = {};
    }

    ~Map() { delete[] maps; }
};

Upvotes: 2

Views: 122

Answers (2)

Matthew P.
Matthew P.

Reputation: 317

It seems like the key misunderstanding here is the difference between stack and heap allocation. Your code would be (almost) correct if we were normally allocating space for an array in a function:

#include <string>

int main() {
    std::string maps[2] = {"Chad", "Zimbabwe"};
}

This is perfectly valid, and works as expected. However, what you're trying to do is dynamically allocate space for an array of strings in memory location maps. This syntax for this would be as follows:

#include <string>

int main() {
    std::string* maps;
    maps = new std::string[2];

    // ... more code ...

    // always free your memory!
    delete[] maps;
}

This tells the OS, "hey! I want some memory for an array, can I have some?" and the OS (hopefully) says "yeah, here you go have fun."

Currently, your code tries to access the second index in unallocated memory, and the OS really doesn't like that.

I hope this helps, and let me know if you need further clarification.

Upvotes: 0

Vlad from Moscow
Vlad from Moscow

Reputation: 310910

These statements

maps[2] = { "Summoner's rift", "Aram" };
mhours_played[2] = {};

do not make sense. maps and mhours_played are pointers that within the body of the constructor have indeterminate values. They are not arrays as you think. For example the expression maps[2] is a scalar object of the type std::string.

Define the constructor at least like

Map() :  mhours_played( new double[2]() ), 
         maps( new std::string[2] { "Summoner's rift", "Aram" } ),
         element_num( 2 )
{
}

and the destructor like 

~Map() 
{ 
    delete[] maps; 
    delete[] mhours_played;
}

Upvotes: 0

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