将结构传递给函数以编辑数组导致C ++ seg错误

Question

Im working on a project to make a word scramble game and currently working on putting the letters in an array of strings. Currently not using any pointers and I worry that that is the cause but I am fairly confused at this point because my assignment requires me to use structs.

Any help would be greatly appreciated, Thanks.

struct definition:

struct puzzle {
int cols;
int rows;
string puzzle[];};

loadPuzzle function

void loadPuzzle(puzzle p){
char c;
p.puzzle[5];
for(int i = 0 ; i <p.rows ; i++){
   p.puzzle[0] = "                      ";
   for(int j = 0 ; j<p.cols ; j++){
      iFS >> c;
      if(!c=='\0')
         p.puzzle[i][j]=c;
   }
 }
 }

main function

int main(int agrc, char* args[]){
//setting default file name to make it easier for testing
string sourceFile = "testfile.txt";
puzzle p;
puzzle *puzz = &p;
//space left to add another do if need be
   do{
      cout << "please enter scramble name: ";
      getline(cin, sourceFile);
      cout << endl;
      iFS.open(sourceFile.c_str());
      if(!iFS.is_open()){
         cerr << "Couldnt open file" << endl;
      }
   }while(!iFS.is_open());
p.cols = getPuzzleCols();
p.rows = getPuzzleRows();
cout << p.rows << p.cols;
loadPuzzle(p);
// displayPuzzle(p);  
}

Answer 1

While you can declare an array with no size

struct puzzle {
int cols;
int rows;
string puzzle[];};

You can't give it a size later through p.puzzle[5]; . This line doesn't actually do anything.

Instead what the no-sized array does is allows one to access memory beyond the end of the struct as if it were an array. This can be useful for clever/old-school ways of allocating arrays, but isn't good for modern C++.

What you should do instead is learn to use std::vector .

Start with:

struct puzzle {
int cols;
int rows;
std::vector<string> puzzle;};

Then read up on how to add elements to it (such as resize or push_back ).

Or if you can't do that for some reason, then you need to give the array its size in its declaration so that it really exists. For example:

struct puzzle {
int cols;
int rows;
string puzzle[5];};