Thread: string with different strlen's

What do you see in the debugger?
There's probably an invisible character in one of them.

You need to get a better look at the string.

Code:

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

void showstring (char *s) {
    int i, j;
	for (i=0;i<strlen(s);i++) {
		if (i && !(i%10)) {
			printf("| ");
			for (j=i-10;j<i;j++) printf("%c", s[j]);
			printf("\n");
		}
		printf("%3d ",s[i]);
	}
	if (i%10) {
		printf("| ");
		for (j=i-i%10+1;j<i;j++) printf("%c", s[j]);
		printf("\n");
	}
}

int main() {
	char str[] = "I would say I do something wrong with the 'null termination'," 
                " but I can't figure it out. Any suggestions ?";

	showstring(str);

    return 0;
}

This will produce output like:

Code:

 73  32 119 111 117 108 100  32 115  97 | I would sa
121  32  73  32 100 111  32 115 111 109 | y I do som
101 116 104 105 110 103  32 119 114 111 | ething wro
110 103  32 119 105 116 104  32 116 104 | ng with th
101  32  39 110 117 108 108  32 116 101 | e 'null te
114 109 105 110  97 116 105 111 110  39 | rmination'
 44  32  98 117 116  32  73  32  99  97 | , but I ca
110  39 116  32 102 105 103 117 114 101 | n't figure
 32 105 116  32 111 117 116  46  32  65 |  it out. A
110 121  32 115 117 103 103 101 115 116 | ny suggest
105 111 110 115  32  63 | ons ?

The text on the right will (probably) look the same in both cases; you need to find the oddball in the values on the left.

Here is the output:

Code:

 window_shift --> 12 en 13
119 105 110 100 111 119  95 115 104 105 102 116   7 | window_shift
119 105 110 100 111 119  95 115 104 105 102 116 | window_shift

What does the 7 do ?

So I found out where it goes wrong in my code:

Code:

// line will look like: window_shift=10
while(fgets(line, sizeof(line), fp) != NULL)
   {
       int len = strlen( line ) - 1;
       if ( len > 0 )
        {
           if(line[len] == '\n')  
             line[len] = 0;        // <---- PROBLEM
           
           int pos = findchar(line, "=") ;

           char *config_key = malloc( pos * sizeof(*config_key) + 1 ) ; // add 1 for 'null termination'
           substring( config_key, line, 0, pos ) ;
           ........
    }
......
void substring(char* dest, const char* src, int start, int stop)
 {
     strncpy( dest, src + start, stop ) ; // doesn't copy '\0' (null termination)
     dest[strlen(dest) ] = '\0' ; // null termination  <--- problem
}

So, the line

Code:

line[len] = 0;

is the problem. If I change it to

Code:

line[len] = '\0';

it works
Are they different ? And why does it work on my mac!

UPDATE: not sure what I just did, but line[len] = '\0' didn't fix it. If I remove the line, that fixes it!!!

Err... actually, there should be no difference. '\0' is a character literal with the value of 0. Since in C character literals are of type int, it really should be the same as just writing 0 (except that 0 would not indicate to the reader that a character is involved here, unlike '\0').