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I am working on implementing tail for an assignment. I have it working correctly however I seem to be getting an error from free at random times. I can't see, to track it down to a pattern or anything besides it is consistent. For example if I call my program as "tail -24 test.in" I would get the the the incorrect checksum error at the same line on multiple runs. However, with different files and even different numbers of lines to print back I will come back without errors. Any idea on how to track down the issue, I've been trying to debug it for hours to no avail. Here is the offending code: lines is defined as a char** and was malloc as: lines = (char**) malloc(nlines * sizeof(char *)); void insert_line(char *s, int len){ printf("\t\tLine Number: %d Putting a %d line into slot: %d\n",processed,len,slot); if(processed > numlines -1){//clean up free(*(lines+slot)); *(lines + slot) = NULL; } *(lines + slot) = (char *) malloc(len * sizeof(char)); if(*(lines + slot) == NULL) exit(EXIT_FAILURE); strcpy(*(lines+slot),s); slot = ++processed % numlines; }

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