Exception thrown: read access violation

Question

i'm a beginner and my english is not well so sorry first. im trying to sum the numbers in a string (for a14fg5pk145 it returns 14+5+145), and it doesn't work: "Exception thrown: read access violation. str was 0x61."

this i my code:

void main()
{
    int x, i;
    char* pp;
    char buffer[SIZE];
    printf("Please enter numbers and letters:\n");
    gets(buffer);
    pp = buffer;
    x = SumStr(*pp);
    printf("%d", x);
}

int SumStr(char* str)
{
    int sum=0, num=0, flag = 0;
    while ((*str) != '\0')
    {
        while (((*str) > '1') && ((*str) < '9'))
        {
            if (flag == 0)
            {
                num += (*str);
                flag = 1;
            }
            else if (flag == 1)
                num = num * 10 + (*str);
            str++;
        }
        if (flag == 0)
            str++;
        sum += num;
        num = 0;
        flag = 0;
    }
    return sum;
}

Another advise: `((*str) > '1') && ((*str) < '9')` is `isdigit(*str)`. Do not reinvent the wheel, use standard libraries. — DYZ, Jan 14 '17 at 07:20
Don't zeros count in your numbers? Actually, you're excluding `0`, `1`, and `9`, which is bit unusual. — Jonathan Leffler, Jan 14 '17 at 07:30
SO isn't a debugging service. Compile with symbols, run the code inside a debugger to trace through the program(s) line by line inspecting the values of the relevant variables to learn what is really going on. If then a *specific* question arises feel free to come back here. — alk, Jan 14 '17 at 13:11

score 2 · Answer 1 · answered Jan 14 '17 at 07:36

First problem with your code which is causing Exception.

x = SumStr(*pp);

it should be

x = SumStr(pp);

Because you should pass address of the string pointer not its first character by attaching asterix.

Second Issue that will not make it work is.

num += (*str);

and

num = num * 10 + (*str);

By (*str) you are actually adding the character ascii value instead of number. This will solve the problem by changing the ascii value to number.

num += (*str) - '0';

num = num * 10 + (*str) - '0';

0 count on my numbers, i forgot it... thank you for your answer! — jov, Jan 14 '17 at 07:46

Sifat Haque · Answer 2 · 2017-01-14T08:02:45.280

This may serve your purpose

#include<stdio.h>
#include<string.h>

int main()
{
    int i, sum = 0, store;
    char str[] = "a14fg5pk145asdasdad6";
    int length = strlen(str);
    for(i = 0; i < length; i++) {
        store = 0;
        while(isdigit(str[i])) {
            store = (store * 10) + (str[i] - '0');
            i++;
        }
        sum += store;
    }
    printf("%d\n", sum);
    return 0;
}

output :

score 0 · Answer 3 · edited May 23 '17 at 12:18

0

Pass pp, not *pp, to the function SumStr. *pp has the type char, and the function expects char *. In fact, you do not even need pp at all, just pass the buffer as the parameter.

Also:

Never use gets(). Because it is impossible to tell without knowing the data in advance how many characters gets() will read, and because gets() will continue to store characters past the end of the buffer, it is extremely dangerous to use. It has been used to break computer security. Use fgets() instead.

edited May 23 '17 at 12:18

Community

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answered Jan 14 '17 at 07:01

DYZ

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The code should either declare `SumStr()` before it is used with a full prototype or moves its definition before `main()` so that the compiler can spot the misuse of the function. As it stands, its hands are tied; it isn't allowed to report the trouble. – Jonathan Leffler Jan 14 '17 at 07:36

Exception thrown: read access violation

3 Answers3