error: ‘for’ loop initial declarations are only allowed in C99 mode [duplicate]

Question

I am getting the below error, what is std=c99/std=gnu99 mode?

source Code:

#include <stdio.h>  void funct(int[5]);  int main()  {             int Arr[5]={1,2,3,4,5};     funct(Arr);     for(int j=0;j<5;j++)     printf("%d",Arr[j]); }  void funct(int p[5]) {         int i,j;         for(i=6,j=0;i<11;i++,j++)             p[j]=i; }   Error Message: hello.c: In function ‘main’: hello.c:11:2: error: ‘for’ loop initial declarations are only allowed in C99 mode for(int j=0;j<5;j++)       ^ hello.c:11:2: note: use option -std=c99 or -std=gnu99 to compile your code` 

Answer 1

This happens because declaring variables inside a for loop wasn't valid C until C99(which is the standard of C published in 1999), you can either declare your counter outside the for as pointed out by others or use the -std=c99 flag to tell the compiler explicitly that you're using this standard and it should interpret it as such.

Answer 2

You need to declare the variable j used for the first for loop before the loop.

    int j;     for(j=0;j<5;j++)     printf("%d",Arr[j]);