C字符串段错误

Question

I am writing a function that sorts enfrobbed data without converting the entire string back to normal. It passes every test case except for when the two strings are equal, when I get a seg-fault every time. I cannot figure out why I get a bad memory access in this case, as I shouldn't be out of the range of the string. Note that the end of the string is expected to be a SPACE, and not a null byte.

int i = 0;
for(; a[i] != " " && b[i] != " "; i++)
{
   char axor = a[i] ^ '*';
   char bxor = b[i] ^ '*';
   //printf("A: %i B: %i \n", axor, bxor);                                         
   if (axor < bxor)
     return -1;                             
   if (axor > bxor)
     return 1;
}
if (a[i] == " " && b[i] == " ") //a and b are equal                                                   
  return 0;
if (a[i] == " ")                   
  return -1;
else //a is greater than b                                                                            
  return 1;

Note that a and b are of type char const* Passing in a = b = "aa", for example, results in a segfault

Answer 1

" " is a char[2] . To get a character, use ' ' .