compiles fine, but crashes after printing first value

[sanzou321]

The program crashes on execution after printing the first value, meant to be printing position of all occurences of an option(struct.option) in string and also printing the option. unique_searchterms is an array of pointers to structs of type options_t and the last pointer in the array points to a struct in which end[0] == '@' to mark the end of the array. Cant see where i'm wrong.

typedef struct {
     int position;   //irrelevant for this question
     char option[Kmax];  //strings of length 4
     char end[2];     //only added to know where the end of an array of pointers to this struct is
} options_t


//snippet from void function
char *string = "blah blah blah";
i = 0;
int pos;

while((unique_searchterms[i].end[0]) != '@'){
      char *term2match = unique_searchterms[i].option; 
      /* finding all occurences of substrings in string using strstr */
      while((string = (strstr(string,term2match))) != NULL){
	char* ptr = strstr(string,term2match);
	string++;
	pos = ptr - string;
	printf("%d \"%s\"\n",pos,term2match);
      }
      i++;	
}

[vlad from moscow]

I do not see any sense in the code snip

      while((string = (strstr(string,term2match))) != NULL){
	char* ptr = strstr(string,term2match);
	string++;
	pos = ptr - string;
	printf("%d \"%s\"\n",pos,term2match);
      }

Let assume that you found term2match in string. In this case string will point to the occurence of term2match. So the next call to strstr

char* ptr = strstr(string,term2match);

will give the same address as string. In this case pos = ptr - string will be always equal to -1. So what is the sense of this code or am I mistaken?

[sanzou321]

oh i guess my logic went out the window there, haha yes you are right, i'm ok with printing -1 over and over again, the problem is that my function keeps crashing as soon as it is done with the while loop with term2match == unique_searchterms[0].option
how do i debug that, do you see anything there that would do that?

[vlad from moscow]

The problem is that after exiting the internal while loop string becames equal to zero. So for the next iteration of the external loop with i equal to 1 your program will be crashed.