Error: 'for' loop initial declarations are only allowed in c99 mode

Question

I've got this problem where I can only compile using the gcc -std=c99 but however, i need it to compile using c89 aka gcc -Wall. This is part of my code where i use the 'for' loop. Please see if you can help me out thank you in advance.

#include<stdio.h>
int main()
{
    int arr[100],i=0,ch;
    int n = 1, sum = 0;
    printf("Check out our selection! \n");
    printf("Airhead - 25 cents\n");
    printf("Fun Dip - 40 cents\n");
    printf("Gummi Bears - 20 cents\n");
    while (n != 0)
    {
        printf("Insert Coins: ");
        scanf("%d",&n);
        arr[i++] = n;
    }

    for(int j=0;j<i;j++)
    {   sum = sum + arr[j];
    }
......

Define the variable j at the start of the function, together with the other variables? — Some programmer dude
– Some programmer dude, Commented May 27, 2017 at 20:06
"i need it to compile using c89 aka gcc -Wall" <- these are different thinks. Why do you need this? — user2371524
– user2371524, Commented May 27, 2017 at 20:08
Possible duplicate of How do I fix "for loop initial declaration used outside C99 mode" GCC error? — Hiko Haieto
– Hiko Haieto, Commented May 27, 2017 at 20:09
gcc without a language option compiles for gnu11 (which is neither c89 nor c99 nor c11). See the gcc manual. For c89 you want gcc -std=c89 -pedantic ... — pmg
– pmg, Commented May 27, 2017 at 20:10

unalignedmemoryaccess · Accepted Answer · 2017-05-27 20:26:21Z

2

This is wrong:

for (int j = 0; j < i; j++) {
    sum = sum + arr[j];
}

You have to initialize j in beginning of function.

 int main() {
    int j;
    ...
    for (j = 0; j < i; j++) {
        sum = sum + arr[j];
    }
}

answered May 27, 2017 at 20:26

unalignedmemoryaccess

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