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POLibrary is empty then seg fault
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copied!<p>Hey guys im doing a project and I keep getting "Library is empty" and then a seg fault, running trough this with gdb its telling me that the error is in my count_list function. But i cannot seem to figure out why? any tips would be appreciated its killing me to be so close to finished and get hung up on this.</p> <pre><code>#include <stdio.h> #include <stdlib.h> #include <string.h> /* Assume max char count in file */ #define MAX 20 /* library struct - DO NOT CHANGE */ typedef struct library { char *genre; char *band; char *album; float rating; struct library *next; }Library; /* Function Prototypes - DO NOT CHANGE */ Library *Read_File(FILE *); void Print(Library *); Library *Create_List(Library *, Library *); Library *Create_Album(char *, char *, char *, float); Library *Merge(Library *, Library *); int Count_List(Library *); void Split_List(Library *, Library **, Library **); Library *Merge_Sort(Library *); Library *Delete_Genre(Library *); void Free_Entry(Library *); Library *Clean(Library *); /* MAIN * Error check file parameter * Call Read_File to fill our list * Print our list * Merge Sort the linked list (by genre) * Delete a genre * Free the list */ int main(int argc, char **argv) { if(argc != 2) { printf("Not enough arguments.\n"); return 0; } FILE *fp = NULL; if((fp = fopen(argv[1], "r")) == NULL) { printf("File can not be opened.\n"); return 0; } Library *Head = NULL; Head = Read_File(fp); Print(Head); Merge_Sort(Head); Print(Head); Head = Delete_Genre(Head); Print(Head); Head = Clean(Head); Print(Head); return 0; } /* Clean() * Delete the linked list, recursively */ Library * Clean(Library *Head) { if(Head) return NULL; Library *Tmp = Head->next; Free_Entry(Head); Clean(Tmp->next); } /* Free_Entry() * wrapper function to free a struct Library */ void Free_Entry(Library *Entry) { free(Entry); } /* Delete_Genre() * Deletes a genre inputted by user * Logic: * prompt user for genre input * traverse list deleting all structs that contain the genre */ Library * Delete_Genre(Library *Head) { if(!Head) { printf("List Empty.\n"); return NULL; } char *input = malloc(MAX * sizeof(char *)); Library *Current = Head; Library *Tail = NULL; printf("Which genre would you like to delete?\n"); scanf("%s", input); while(Current) { if(strcmp(Current->genre, input)) { if(Current = Head) { Head = Head->next; Free_Entry(Current); Current = Head; } else Tail->next = Current->next; } else Current = Current->next; } } /* Read_File() * Open file fp * Create a struct from information in text file * Link our list with newly created struct */ Library * Read_File(FILE *fp) { Library *Head, *Entry; Head = Entry = NULL; char *genre, *band, *album; float rating; while(1) { fscanf(fp, "%s %s %s %f", &genre, &band, &album, &rating); if(!feof(fp)) break; Entry = Create_Album(genre, band, album, rating); Head = Create_List(Entry, Head); } return Head; } /* Print() * Print the linked list */ void Print(Library *Head) { if(!Head) { printf("Library is empty.\n"); return; } while(Head) { printf("%20s %20s %20s %20.2f \n", Head->genre, Head->band, Head->album, Head->rating); Head = Head->next; } printf("\n\n"); //return Head; } /* Create_Album * Create a struct and assign the given args to it as appropriate */ Library * Create_Album(char *genre, char *band, char *album, float rating) { Library *Entry = malloc(sizeof(Library)); strcpy(Entry->genre, genre); strcpy(Entry->band, band); strcpy(Entry->album, album); Entry->rating = rating; Entry->next = NULL; return Entry; } /* Create_List() * Push Entry onto our List */ Library * Create_List(Library *Head, Library *Entry) { if(!Head) return Entry; Entry->next = Head; return Entry; } /* Merge_Sort() * Recursively split our list between Left and Right * Merge our Left and Right lists */ Library * Merge_Sort(Library *Head) { Library *Tmp = Head; Library *Left, *Right, *Result; Left = Right = Result = NULL; int count = Count_List(Head); if(count = 1) return Tmp; Left = Merge_Sort(Left); Right = Merge_Sort(Right); Result = Merge(Left, Right); return Result; } /* Split_List() * split our list in half */ void Split_List(Library *Head, Library **Left, Library **Right) { int size = Count_List(Head); int i; Library *Tmp = Head; *Left = Head; for(i=1; i<size/2; ++i) Tmp=Tmp->next; *Right = Tmp->next; Tmp->next = NULL; } /* Merge() * Merge two linked lists Left and Right together in sorted order */ Library * Merge(Library *Left, Library *Right) { Library *Result, *Tmp; Result = Tmp = NULL; if(strcmp(Left->genre, Right->genre) <= 0) { Result = Left; Left = Left->next; } else { Result = Right; Right = Right->next; } Tmp = Result; while(Left != NULL && Right != NULL) { if(Left != NULL && Right!= NULL) { if (strcmp(Left->genre, Right->genre) <= 0) { Tmp->next = Left; Left = Left->next; } else { Tmp->next = Right; Right = Right->next; } Tmp = Tmp->next; } } return Result; } /* Count_List() * Count the number of elements in a linked list */ int Count_List(Library *Head) { Library *Tmp = Head; int count = 0; while(Tmp->next != NULL) { count++; Tmp = Tmp->next; } } </code></pre>

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