CODEWITHSUNDEEP
c++arraysstringmemory-managementdynamic
user2889285
user2889285

Reputation: 3

dynamically allocated string array

When I attempt to run this code it crashes. There are no error messages. When the program compiles and runs, it just displays the windows 7 message, "this program has stopped working.":

void readGameFile(string ** entries, int * num_entries, string ** story, int * num_lines)
{
    ifstream madlib("madlibs1.txt");
    string line;
    getline(madlib, line);
    *num_entries=stoi(line);
    *entries=new string [*num_entries];
    for (int i=0; i<*num_entries; i++)
    {
        getline(madlib,*entries[i]);
    }

I did a few tests, and it seems to assign entries[0] a value, and then crashes when attempting to assign entries[1] a value. I am forced to use this function name, with those function parameters and parameter types specifically. I also may not use malloc, vector or other answers I've seen.

Upvotes: 0

Views: 180

Answers (1)

James Kanze
James Kanze

Reputation: 154027

I think the issue is one of precedence: you almost certainly want:

getline( madlib, (*entries)[i]) );

Otherwise, you're indexing from the string**, then dereferencing: *(entries[i]).

You also want to check the results of getline, possibly in the loop:

for ( int i = 0; madlib && i != *num_entries; ++ i )...

as well as before the std::stoi.

And finally: I don't know why you are forced to use this function signature. It is horrible C++, and you should never write anything like this. Logically, std::vector<string> would be a better solution, but even without it: your function has 4 out parameters. This would be better handled by returning a struct. And failing that, out parameters in C++ are usually implemented by non-const reference, not by a pointer. While there are arguments for using the pointer in some cases, when it results in a pointer to a pointer, it's evil. If nothing else:

bool        //  Because we have to indicate whether it succeed or failed
readGameFile( std::string* &entries, int &num_entries, std::string* &story, int &num_lines )
//  ...

(This actually looks more like it should be constructor, however, of a class with two data elements, entries and story.)

Upvotes: 1

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