i have problems with valgrind,

i created this class: 

```
class shop {

    private:
       vector<vector<string> > products_;

    public:
           shop(string ProductFile);
           FindMinPrice(string product);
}

    //method in the cpp file
    vector<string> shop::FindMinPrice(string product){
         string ProductName=(string)products_[0][0];

    }

```

i didn't write the entire code but its work fine with the GCC compiler.
when i run valgrind check it shows:
invalid read of size 8 
and in eclipse it send me to the ProductName line.

what is wrong with the design ? and how so that the GCC compile and run but VALGRIND collapse?

thank you.