Error 1 in the Chinese version of C Primer Plus (Sixth edition)

1#include <stdio.h>2#include <stdlib.h>3#include <string.h>4 #defineTsize 455 6 structFilm {7     CharTitle[tsize];8     intrating;9     structFilm *Next;Ten }; One Char* S_gets (Char* St,intn); A  - intMainvoid) - { the     structFilm * head =NULL; -     structFilm *prev; -     structFilm *Current ; -     CharInput[tsize]; +  -Puts"Enter First movie title:"); +      while(S_gets (input, tsize)! = NULL && input[0] !=' /') A     { atCurrent = (structFilm *)malloc(sizeof(structfilm)); -         if(Head = =NULL) -Head =Current ; -         Else -Prev->next =Current ; -Current->next =NULL; instrcpy (current->title, input); -Puts"Enter your rating <0-10>:"); toscanf"%d", &current->rating); +          while(GetChar ()! ='\ n') -             Continue; thePuts"Enter Next movie title (empty line to stop):"); *Prev =Current ; $     }Panax Notoginseng  -     if(Head = =NULL) theprintf"No data entered."); +     Else Aprintf"Here is the movie list:\n"); theCurrent =head; +      while(Current! =NULL) -     { $printf"Movie:%s Rating:%d\n", $Current->title, current->rating); -Current = Current->Next; -     } the  -Current =head;Wuyi      while(Current! =NULL) the     { -Current =head; WuHead = current->Next; -          Free(current); About     } $printf"bye!\n"); -  -     return 0; - } A  + Char* S_gets (Char* St,intN) the { -     Char*Ret_val; $     Char*find; the  theRet_val =Fgets (St, N, stdin); the     if(Ret_val) the     { -Find = STRCHR (St,'\ n'); in         if(Find) the*find =' /'; the         Else About              while(GetChar ()! ='\ n') the                 Continue; the     } the  +     returnRet_val; -}

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The above code is from "C Primer Plus" (sixth edition) Chinese version, 第573-574 page.

There is an error in line 51st of the code.

I do not know whether the error is printing wrong, or the original book is wrong. Noted here.

Correction Code:

is to change the while of line 51st (current! = NULL) to

while (head! = NULL) is ready.

The reasons are as follows:

Add some output between the 第51-56 line code as follows:

1      while(Current! =NULL)2     {3printf"current1 =%p\n", current);4printf"head1 =%p\n\n", head);5Current =head;6printf"Current2 =%p\n", current);7printf"head2 =%p\n\n", head);8Head = current->Next;9printf"Current3 =%p\n", current);Tenprintf"head3 =%p\n\n", head); One          Free(current); Aprintf"current4 =%p\n", current); -printf"head4 =%p\n\n", head); -}

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The output results are as follows:

As you can see from the above output, the last head2 pointer is already 00000000 and is a pointer to an unknown address. So releasing a current again will make a mistake.

Corrected output:

Error 1 in the Chinese version of C Primer Plus (Sixth edition)