KERN_INVALID_ADDRESS has me stumped

Question

I keep getting this error trying to run the debugger:

Program received signal EXC_BAD_ACCESS, Could not access memory.
Reason: KERN_INVALID_ADDRESS at address: 0x0000000000000000
0x00007fff8c2414f0 in strlen ()

Here is my code:

#include <stdio.h>
#include <cs50.h>
#include <string.h>
#include <ctype.h>
#include <stdlib.h>

int main(int argc, char *argv[])
{
    char s2[25];
    strcpy(s2, argv[1]);
    int keyLen = strlen(s2);
    printf("Please enter a string of text to be encrypted!\n");
    string p = GetString();
    for (int i = 0, n = strlen(p); i < n; i++)
    {
        if (isupper(p[i])){
        int sum = (p[i] - 'A') + (s2[i % keyLen] - 'A');
        char c = 'A' + sum%26;
        printf("%c", c);
        }
    }
    printf("\n");
    printf("%d\n", keyLen);

}

I can compile the code with no errors and it works like it should. I am running the debugger to step into the for loop and look at what the math is doing to better understand it.

Is there at least one argument being supplied to the program, which is no more than 24 characters? — hmjd, Oct 19 '12 at 14:36
this is much more likely than my answer! (especially since we don't know for sure where it's crashing...) — mfsiega, Oct 19 '12 at 14:40

score 1 · Answer 1 · answered Oct 19 '12 at 14:37

1

If GetString() returns null, then calling strlen(null) will give this error. Other errors on the part of GetString() could be causing this as well.

answered Oct 19 '12 at 14:37

mfsiega

2,852
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score 1 · Answer 2 · answered Oct 19 '12 at 14:44

1

What is type 'string' in C? Strlen() expects C-type array and not some custom 'string' type. (+ there is a possibility of null input as pointed above)

answered Oct 19 '12 at 14:44

SomeWittyUsername

18,025
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`` contains `typedef char *string;` — for better or worse. – Jonathan Leffler Aug 08 '16 at 01:49

score 0 · Accepted Answer · answered Oct 19 '12 at 14:42

0

I finally got it thanks to hmjd I was running it incorrectly I would start the program

gdb vignere HHHHH

Which is incorrect I ran it

gdb vignere
run HHHHHH

and it worked perfect!

answered Oct 19 '12 at 14:42

Yamaha32088

4,125
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2

You should add an `if (argc > 1)` check to the program to avoid this. – hmjd Oct 19 '12 at 14:44

KERN_INVALID_ADDRESS has me stumped

3 Answers3