將節點添加到鏈接列表時發生堆損壞

Question

我是C新手，無所適從。幾個小時我一直在撞牆。

我創建了兩個struct s來保存我的鏈表節點。第一個，struct movie顯然擁有電影。第二個struct actor是將演員節點添加到電影節點。

struct movie { 
    struct movie* next; 
    struct actor* actors; 
    char name[100]; 
    int rating; 
    genre type; 
} *list = NULL; 


// contains actor information 
struct actor { 
    struct actor* next; 
    char name[100]; 
}; 

麻煩的是當我嘗試將actor添加到movie。

int add_actor(char* movie_name, char* actor_name) 
{ 
    struct movie *tmp = list, *tmpList = NULL; 
    struct actor *tmpActor = NULL, *current = NULL; 

    //check if movie name exists in list 
    while (tmp != NULL) { 
     if (strcmp(tmp->name, movie_name) == 0) { 
      tmpList = tmp; 
     } 
     tmp = tmp->next; 
    }                  //make sure newActor->next is pointing to the correct place 
    if (tmpList == NULL) { return 0; } //if movie in not in list, return 0 

    //The problem occurs most often at this line, with the exception below. 
    //Exception thrown at 0x77433500 (ntdll.dll) in hw7.exe: 0xC0000005: Access violation reading location 0x006F4E42 
    struct actor *newActor = (struct actor*)malloc(sizeof(struct actor));//create new actor node 

    if (tmpList->actors == NULL){ //if the movie has no actors in list 
     tmpList->actors = newActor; 
     strcpy(newActor->name, actor_name); 
     newActor->next = NULL; 
     return 1; 
    } 
    else { //check if actor name already exists in list 
     while (tmpActor != NULL) { 
      if (strcmp(tmpActor->name, actor_name) == 0) { 
       return -1; //if actor already exists return -1 
      } 
      tmpActor = tmpActor->next; 
     } 

     tmpActor = tmp->actors; 

     //insert at beginning of list 
     if (strcmp(actor_name, tmpActor->name) >= 0) { 
      newActor->next = tmpActor; 
      tmpActor = newActor; 
      return 1; 
     } 
     //insert actor in arbitrary position 
     while (tmpActor != NULL && strcmp(actor_name, tmpActor->name)<0) { 
      current = tmpActor; 
      tmpActor = tmpActor->next; 
     } 
     newActor->next = current->next; 
     strcpy(newActor->name, actor_name); 
     current->next = newActor; 
     return 1; 
    } 
} 

至多我已經能夠將兩個演員添加到兩個不同的電影。問題總是出現在第三項。

這裏是拋出

更新異常：

通過我的代碼精心挑選後，我發現了一個明顯的錯誤。當傳遞大於幾個字符的內容時，程序會崩潰。當我聲明傳遞給add_actor函數的指針變量movie_name和actor_name時，我沒有爲較大的名稱分配足夠的空間。

char* movie_name = (char*)malloc(sizeof(char*)); 
char* actor_name = (char*)malloc(sizeof(char*)); 

變化後：

char* movie_name = (char*)malloc(5000*sizeof(char*)); 
char* actor_name = (char*)malloc(5000*sizeof(char*)); 

我能添加的電影和演員沒有崩潰。

Answer 1

我看到兩個錯誤。
儘管這兩者中的任何一個都不可能是崩潰的來源，因爲它們都不會在您的測試用例中執行。 （除非你給添加兩個演員，每個電影 - 這個問題很難解釋）。
最終的原因可能在於添加電影的功能或其他地方。
當堆已經損壞時，你可以肯定地說它發生在程序開始和崩潰之間的某個時刻。

但無論如何，我會提到這些錯誤...

一：

當你到了這一點：

tmpActor = tmp->actors; 

tmp保證是NULL從你的第一個循環。
你可能是指

tmpActor = tmpList->actors; 

二：

當你在這裏：

//insert at beginning of list 
    if (strcmp(actor_name, tmpActor->name) >= 0) { 
     newActor->next = tmpActor; 
     tmpActor = newActor; 
     return 1; 
    } 

分配新演員tmpActor，這是一個局部變量。

我想你應該

tmpList->actors = newActor; 

三和更換

tmpActor = newActor; 

：不投的malloc結果。

Answer 2

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


typedef struct movie MOVIE; 
typedef struct actor ACTOR; 



typedef enum { 
    Action, 
    Documentary, 
    Animation /*etc ...*/ 
}genre; 
struct movie{ 
    MOVIE* next; 
    ACTOR* actors; 
    char name[100]; 
    int rating;  
    genre type; 
} ; 
// contains actor information 

struct actor { 
    ACTOR* next; 
    char name[100]; 
}; 

MOVIE *list = NULL; 



/*_______________________________________________________ 
*/ 
MOVIE *List_FindMovie(const char *movie_name){ 
    MOVIE *tmp = list; 

    while (tmp != NULL) { 
     if (_stricmp(tmp->name, movie_name) == 0) { 
      return tmp; 
     }   
     tmp = tmp->next; 
    } 
    return NULL; 
} 

/*_______________________________________________________ 
*/ 
ACTOR *Movie_FindActor(MOVIE *movie,const char*actor_name){ 
    ACTOR *tmpActor=movie->actors; 
    while(tmpActor){ 
     if(_stricmp(tmpActor->name,actor_name)==0) 
      return tmpActor; 
     tmpActor=tmpActor->next; 
    } 
    return NULL; 
} 
/*_______________________________________________________ 
*/ 
int List_ActorInfo(const char *actor_name){ 
    MOVIE *tmp = list; 
    int nmovies=0; 
    printf("Actor '%s' participations:\n",actor_name); 
    while (tmp != NULL) { 
     if(Movie_FindActor(tmp,actor_name)){ 
      nmovies++; 
      printf("\t- %s\n",tmp->name); 
     } 
     tmp = tmp->next; 
    } 

    if(nmovies) 
     printf("\t Total: %d movies\n\n",nmovies); 
    else 
     printf("\t None\n\n"); 
    return nmovies; 
} 
/*_______________________________________________________ 
*/ 
ACTOR *NewActor(const char*actor_name){ 
    ACTOR *NewActor=calloc(1,sizeof(ACTOR)); 
    strcpy(NewActor->name,actor_name); 
    return NewActor; 
} 
/*_______________________________________________________ 
*/ 
ACTOR *Movie_AddActor(MOVIE *movie,ACTOR *NewActor){ 
    if(!movie->actors){ 
     movie->actors=NewActor; 
    }else{ 
     ACTOR *prevActor=NULL,*current=movie->actors; 
     while(_stricmp(current->name,NewActor->name)<0){ 

      prevActor=current; 
      current=current->next; 
      if(!current)break; 
     } 
      NewActor->next=current; 
      if(prevActor) 
       prevActor->next=NewActor; 
      else 
       movie->actors=NewActor; 

    } 
    return NewActor; 
} 


/*_______________________________________________________ 
*/ 
MOVIE * List_AddMovie(const char *movie_name,genre type){ 
    MOVIE *movie,*tmpMovie; 
    if(movie=List_FindMovie(movie_name)) return 0; 

    movie=calloc(1,sizeof(MOVIE)); 
    strcpy(movie->name,movie_name); 
    movie->type=type; 
    if(!list) 
     list=movie; 
    else{ 
     tmpMovie=list; 
     while(tmpMovie->next) 
      tmpMovie=tmpMovie->next; 
     tmpMovie->next=movie; 
    } 
    return movie; 
} 
/*_______________________________________________________ 
*/ 
void Movie_PrintActors(MOVIE *movie){ 
    ACTOR *actor=movie->actors; 
    printf("Actors in Movie '%s':\n",movie->name); 
    while(actor){ 
     printf("\t%s\n",actor->name); 
     actor=actor->next; 
    } 
    printf("\n"); 

    return; 
} 
/*_______________________________________________________ 
*/ 

int main(){ 
    MOVIE *mv; 


    List_AddMovie("Dogs",0); 
    mv=List_AddMovie("Dragons",0); 


    if(!mv){ 
     printf("failed to add movie\n"); 
     exit(-1); 
    } 
    Movie_AddActor(mv,NewActor("Z")); 
    Movie_AddActor(mv,NewActor("C")); 
    Movie_AddActor(mv,NewActor("A")); 
    Movie_AddActor(mv,NewActor("Cat8")); 
    Movie_PrintActors(mv); 

    mv=List_FindMovie("Dogs"); 
    Movie_AddActor(mv,NewActor("Dog1")); 
    Movie_AddActor(mv,NewActor("Dog3")); 
    Movie_AddActor(mv,NewActor("Dog6")); 
    Movie_AddActor(mv,NewActor("Cat8")); 

    Movie_PrintActors(mv); 

    List_ActorInfo("Bruce Lee"); 
    List_ActorInfo("Cat8"); 
    return 0; 

}