How Do I Fix a 'expression must have a constant value' Syntax Error When Declaring Arrays in C ?

Troubleshooting: Syntax Error in Array Declaration

When attempting to create an array from declared variables, you may encounter the error:

expression must have a constant value

This error arises because arrays in C require constant expressions for their sizes.

Resolving the Error

To resolve this error, you have two options:

1. Create a Dynamic Array on the Heap:

Dynamic arrays allow for variable sizing by allocating memory on the heap. However, you must manually allocate and deallocate this memory using the new and delete operators:

// Allocate the array
int** arr = new int*[row];
for (int i = 0; i < row; i++)
    arr[i] = new int[col];

// Use the array
// ...

// Deallocate the array
for (int i = 0; i < row; i++)
    delete[] arr[i];
delete[] arr;

2. Declare Array Size as Constant:

To maintain a fixed-size array, you must declare the dimensions as constant:

const int row = 8;
const int col = 8;
int arr[row][col];

Cautions

The syntax you provided, int [row][col];, is incorrect as it does not specify a variable name for the array.

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