Arrays are not storing values in the loop

Question

That's my C code. I'm trying to store values in my arrays using the for-loop but nothing is stored and only the value of the variable trackingCodes changes. I don't where the errors comes from . No compiling errors

#include <stdio.h>

int main(void) {
int trackingCodes = 0;
char typeCode[trackingCodes];
int codeLength [trackingCodes];
int byteChar = 0;
int byteInt = 0;
int byteDouble = 0;
int j = 0;
int totalBytes = 0;
int totalByteDouble = 0;
int totalByteInt = 0;
int totalByteChar = 0;


scanf("%d", &trackingCodes);

for ( j = 0; j < trackingCodes; j++)
{
    scanf("%d %c", &codeLength[j], &typeCode[j]);
    if (typeCode[j] == 'c')
    {
        byteChar = codeLength[j] * sizeof(char);
        totalByteChar = totalByteChar + byteChar;

    }
     else if (typeCode[j] == 'i')
    {
        byteInt = codeLength[j] * sizeof(int);
        totalByteInt = totalByteInt + byteInt;

    }
     else if (typeCode[j] == 'd')
    {
        byteDouble = codeLength[j] * sizeof(double);
        totalByteDouble = totalByteDouble + byteDouble;

    } 

}

    totalBytes = totalByteChar + totalByteDouble + totalByteInt;
    int t = 0;

    for(t = 0; t < trackingCodes; t++){
        if(codeLength[t] != 'i' && codeLength[t] != 'c' && codeLength[t] != 'd'){
            printf("Invalid Tracking code type");
            return 0;
        }
    }

    printf("%d bytes\n", totalBytes);



    return 0;
}```

Your arrays are size zero. They don't get sized retroactively. — Fred Larson
– Fred Larson, Commented Jan 8, 2020 at 20:51

4386427 · Accepted Answer · 2020-01-08 21:12:03Z

2

You need to move the array definition so that it is after you have read trackingCodes. In this way you create a Variable Length Array with the size scanned. Like:

scanf("%d", &trackingCodes);

char typeCode[trackingCodes];
int codeLength [trackingCodes];

And... Always check the return value from scanf - that is:

if (scanf("%d", &trackingCodes) != 1)
{
    // error handling
}

answered Jan 8, 2020 at 21:12

4386427

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Comments

Govind Parmar · Accepted Answer · 2020-01-08 22:49:04Z

0

I think you think the code:

int trackingCodes = 0;
char typeCode[trackingCode];

Will indefinitely bind the size of typeCode to the value of trackingCodes. It's actually going to declare typeCode with the size of the current value of trackingCodes.

Solutions are to either scan your input from stdin as covered in @4386427's answer, or to allocate it with dynamic memory management (malloc/free and co.)

answered Jan 8, 2020 at 22:49

Govind Parmar

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