Initializing variable length array [duplicate]

问题:

This question already has answers here:

C compile error: “Variable-sized object may not be initialized” (7 answers)

C error “variable-sized object may not be initialized” [duplicate] (3 answers)

gcc complains: variable-sized object may not be initialized (3 answers)

Closed 2 years ago.

On initializing a Variable length array compiler gives an error message:

[Error] variable-sized object may not be initialized  

Code snippet:

int n; 
printf("Enter size of magic square: ");
scanf("%d",&n);

int board[n][n] = {0};

How should Variable Length arrays be initialized? And why it's all elements are not initialized to 0 in the way give below;

   int board[n][n];
   board[n][n] = {0};

?

回答1:

VLAs cannot be initialized by any form of initialization syntax. You have to assign the initial values to your array elements after the declaration in whichever way you prefer.

C11: 6.7.9 Initialization (p2 and p3):

No initializer shall attempt to provide a value for an object not contained within the entity being initialized.

The type of the entity to be initialized shall be an array of unknown size or a complete object type that is not a variable length array type.

回答2:

You'll have to use memset:

memset(board, 0, sizeof board);

回答3:

1.You can simply initialize the array as follows-

int n; 
printf("Enter size of magic square: ");
scanf("%d",&n);

int board[n][n];
for(int i=0; i<n; i++)
   for(int j=0; j<n; j++)
   {
      board[i][j] = 0;
   }
}

2. memset() should only be used when you want to set the array to "0".