file io - Solving Error in `./recover': free(): invalid next size (normal): 0x0000000001ddd270 *** Aborted in c -


code must read 512 bytes @ time file has raw jpegs in order retrieve them. when jpeg found, following blocks of 512 bytes stored in a file until new jpeg found, once new jpeg found, file img closed , opened new store new image. code runs fine if comment or erase fclose(img); line, othwerwise shows error above.

here's code

#include <stdio.h> #include <cs50.h> #include <stdlib.h>   int main (int argc, char *argv[]){  if(argc != 2){      fprintf(stderr, "usage: ./recovery image\n");     return 1;  }  file *card = fopen(argv[1], "r");  if (card == null){      fprintf(stderr, "cannot open image\n");     return 2;  }  file *buffer1 = malloc(sizeof(card));  int n = 0; int picsnum = 0;  while(fread(buffer1, 512, 1, card)){      n ++;  }  //printf("%i", n);  bool foundjpeg = false; int j = 0; bool fstjpeg = false; file *img = null; int counter = 0;  fseek(card, 0, seek_set);  for(int = 0; < n; i++){       unsigned char fst;     unsigned char snd;     unsigned char thrd;     unsigned char fth;     unsigned char buffer2[508];      fread(&fst, 1, 1, card);     fread(&snd, 1, 1, card);     fread(&thrd, 1, 1, card);     fread(&fth, 1, 1, card);     fread(buffer2, 508, 1, card);     //printf("%i,%i,%i,%i,", fst, snd, thrd, fth);      if(fst == 0xff && snd == 0xd8 && thrd == 0xff && (fth & 0xf0) == 0xe0){          printf("found\n");          if(fstjpeg){              fclose(img);          }          printf("%i,%i,%i,%i,", fst, snd, thrd, fth);         foundjpeg = true;         picsnum++;         fstjpeg = true;          char jpeg[8];         sprintf(jpeg, "%03i.jpg", j);         j++;         img = fopen(jpeg, "w");      } else {          foundjpeg = false;      }      if(fstjpeg){          fwrite(&fst, 1, 1, card);         fwrite(&snd, 1, 1, card);         fwrite(&thrd, 1, 1, card);         fwrite(&fth, 1, 1, card);         fwrite(buffer2, 508, 1, card);         counter++;         printf("%i,", counter);      }  }      fclose(card);     printf("%i,\n", picsnum);  }

what think

file *buffer1 = malloc(sizeof(card));

is doing? creating buffer 4 or 8 bytes long. (the size of file * ). told read 512 bytes @ once. , char * buffer not file *. how doing.

char *buffer1 = malloc(512);

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