sprintf bug or not?

[akko]

Why does the following code produce an access violation error? (PC ver 7.00.350)

Code: [Select]

#include <stdio.h>
#include <stdlib.h>

int main(void)
{   char *c = "xxx...xxx";

   sprintf(c+3, "%d", 123);
   printf(c); // should print: xxx123
   return 0;
}


[CommonTater]

It's because you are trying to change a string constant.
 

Code: [Select]

#include <stdio.h>
#include <stdlib.h>

int main(void)
{   char c[12] = "xxx...xxx";

   sprintf(&c[3], "%d", 123);
   printf(c); // should print: xxx123
   return 0;
}

Or, most correctly....
 

Code: [Select]

#include <stdio.h>
#include <stdlib.h>

int main(void)
{   char c[8];

   sprintf(c, "xxx%d", 123);
   printf(c); // should print: xxx123
   return 0;
}

 

[akko]

Thanx -- I "should" have thought about it but...   

This one works okay too:

Code: [Select]

#include <stdio.h>
#include <stdlib.h>

int main(void)
{ char c[] = "xxx...xxx";  // <--- c[]  instead of  *c

sprintf(c+3, "%d", 123);
printf(c); // should print: xxx123
return 0;
}


[CommonTater]

Thanx -- I "should" have thought about it but...   

No worries... glad I could help.

[czerny]

Why does the following code produce an access violation error? (PC ver 7.00.350)

Don't know if it is clear to you. The error is not in the sprintf call but in

Code: [Select]

char *c = "xxx...xxx";


[CommonTater]

Don't know if it is clear to you. The error is not in the sprintf call but in

Code: [Select]

char *c = "xxx...xxx";


Hi Czerny:
There's nothing wrong with using a pointer to a string constant, it's done all the time.

The access violation comes from attempting to change a constant value; the string in this case.