The C99 standard allows variable sized arrays (see this). But, unlike the normal arrays, variable sized arrays cannot be initialized.
For example, the following program compiles and runs fine on a C99 compatible compiler.
#include<stdio.h> int main()
{ int M = 2;
int arr[M][M];
int i, j;
for (i = 0; i < M; i++)
{
for (j = 0; j < M; j++)
{
arr[i][j] = 0;
printf ( "%d " , arr[i][j]);
}
printf ( "\n" );
}
return 0;
} |
Output:
0 0 0 0
But the following fails with compilation error.
#include<stdio.h> int main()
{ int M = 2;
int arr[M][M] = {0}; // Trying to initialize all values as 0
int i, j;
for (i = 0; i < M; i++)
{
for (j = 0; j < M; j++)
printf ( "%d " , arr[i][j]);
printf ( "\n" );
}
return 0;
} |
Output:
Compiler Error: variable-sized object may not be initialized
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