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

#define BUFFSIZE 3 /* >= 2 */
char *getline(FILE *fp)
{
  static char inbuff[BUFFSIZE];
  char *outbuff_malloc, *tmpbuff;
  char *p, *q;
  int fEOL;
  if ((outbuff_malloc = malloc(1)) == NULL) {
    return NULL;
  }
  *outbuff_malloc = '\0';
  fEOL = 0;
  do {
    if ((q = fgets(inbuff, BUFFSIZE, fp)) == NULL)
      break;
    for (p = inbuff; *p != '\0'; p++)
      ;
    if (*(p - 1) == '\n') {
      *(p - 1) = '\0';
      fEOL = 1;
    }
    if ((tmpbuff = realloc(outbuff_malloc, strlen(outbuff_malloc) + strlen(inbuff) + 1)) ==NULL) {
      free(outbuff_malloc);
      return NULL;
    }
    strcat(tmpbuff, inbuff);
    outbuff_malloc = tmpbuff;
  } while (!fEOL);
  if (q == NULL) {
    free(outbuff_malloc);
    return NULL;
  }
  return outbuff_malloc;
}

int main()
{
  char *p, *q;
  int sp, sq;
  int flag = 0;
  printf("input string 1: ");
  if ((p = getline(stdin)) != NULL) {
    printf("input string 2: ");
    if ((q = getline(stdin)) != NULL) {
      sp = strlen(p);
      sq = strlen(q);
      if (sp < sq || sp == 0 || sq == 0) {
        printf("no matched.\n");
      } else {
        unsigned int i, j;
        for (i = 0; i < sp - sq + 1; i++) {
          for (j = 0; j < sq; j++) {
            if (p[i + j] != q[j])
              break;
          }
          if (j == strlen(q)) {
            printf("matched %d - %d\n", i, i + strlen(q) - 1);
            flag = 1;
          }
        }
        if (flag == 0)
          printf("no match.\n");
      }
    }
  }
  free(p);
  free(q);
  return 0;
}
/* end */

memory clobbered before allocated block

Exited: ExitFailure 127