Ich habe ein kleines Programm geschrieben, mit dem der Benutzer eine Datei lesen, eine kleine "Datenbank" erstellen und Einträge erstellen oder löschen kann. Wenn ich versuche, die Funktion zu verwenden, stürzt es ab.C - Absturz bei der Verwendung von Realloc auf einem Zeiger in einem Struct
nicht sicher, ob ich etwas falsch zu machen, bin wohl aber, da ich zu C recht neu bin
Also versuche ich es auf diese Weise zu tun:
StudentDB database;
//More code in between, that does include malloc()
database->students = realloc(database->students, (database->numberOfStudents + 1) * sizeof(Student));
//It crashes when it gets to that part.
Was ich bin Zu versuchen, zu tun, ist die Realloc() -Funktion für einen Zeiger, der innerhalb einer Struktur ist.
Dies ist das gesamte Programm so weit:
#include <stdio.h>
#include <stdlib.h>
typedef struct Lesson {
char *name;
int semester;
float grade;
} Lesson;
typedef struct Student {
char *name;
char *surname;
int id;
int numberOfLessons;
Lesson *lesson;
} Student;
typedef struct Database {
int numberOfStudents;
Student *student;
} StudentDB;
static int maxNameSize = 100;
static int autoclear = 1;
void addStudent(FILE *studentFile, StudentDB *database) {
database->numberOfStudents++;
printf("\nAdded +1 to number of students");
database->student = realloc(&database->student, 10);
//
// printf("Name of the student: ");
// scanf("%s", database.student[database.numberOfStudents].name);
}
void clear() {
if(autoclear) {
system("cls");
}
}
Lesson getNextLesson(FILE *studentFile) {
Lesson lesson;
lesson.name = malloc(maxNameSize * sizeof(char));
if(!lesson.name) { printf("Memory Allocation has failed. Exiting the program!"); exit(0); }
fscanf(studentFile, "%s", lesson.name);
fscanf(studentFile, "%d", &lesson.semester);
fscanf(studentFile, "%f", &lesson.grade);
printf("\n\t%s %d || %.2f\n", lesson.name, lesson.semester, lesson.grade);
return lesson;
}
Student getNextStudent(FILE *studentFile) {
Student student;
student.name = malloc(maxNameSize * sizeof(char));
if(!student.name) { printf("Memory Allocation has failed. Exiting the program!"); exit(0); }
fscanf(studentFile, "%s", student.name);
student.surname = malloc(maxNameSize * sizeof(char));
if(!student.surname) { printf("Memory Allocation has failed. Exiting the program!"); exit(0); }
fscanf(studentFile, "%s", student.surname);
fscanf(studentFile, "%d", &student.id);
fscanf(studentFile, "%d", &student.numberOfLessons);
printf("%d || %s %s || %d\n", student.id, student.name, student.surname, student.numberOfLessons);
int lesson;
student.lesson = malloc(student.numberOfLessons * sizeof(Lesson));
for(lesson = 0; lesson < student.numberOfLessons; lesson++) {
student.lesson[lesson] = getNextLesson(studentFile);
}
return student;
}
void loadStudents() {
}
void run(FILE *studentFile, StudentDB *database) {
int answer;
do {
clear();
answer = menu();
switch(answer) {
case 1: {
break;
}
case 2: {
break;
}
case 3: {
addStudent(studentFile, &database);
break;
}
case 4: {
break;
}
}
} while(answer < 0 || answer > 9);
}
int menu() {
int answer;
printf("1. Load students records from file\n");
printf("2. Save students records to file\n");
printf("3. Add a student record\n");
printf("4. Delete a student record by student id\n");
printf("5. Display a student record by student id\n");
printf("6. Display a student record by student surname\n");
printf("7. Display all student records\n");
printf("8. Find the lesson average for all students\n");
printf("9. Exit\n");
printf("Enter the number of the thing you would like to do: ");
// scanf("%d", &answer);
return 3;
}
void programInfo() {
printf("\n\n====================================================\n\tProgram Info\n\n This program was created by KKosyfarinis\n\n [email protected]\n====================================================\n\n");
}
void readData(FILE *studentFile, StudentDB *db) {
int i;
printf("Running the loop\n");
for(i = 0; i < db->numberOfStudents; i++) {
printf("=====================\n\n\tStudent #%d\n", i);
db->student[i] = getNextStudent(studentFile);
printf("\n\tCompleted\n\n=====================\n");
}
clear();
}
void saveStudents() {
}
void main() {
system("color 02");
system("@echo off");
FILE *studentFile;
StudentDB database;
studentFile = fopen("students.txt", "r+w");
int numberOfStudents;
//Set the number of students
fscanf(studentFile, "%d", &database.numberOfStudents);
//Prints the number of students
printf("Number of students: %d\n", database.numberOfStudents);
//Set the memory allocation
database.student = malloc(database.numberOfStudents * sizeof(Student));
if(!database.student) {
printf("The memory allocation has failed. Exiting the program!");
exit(0);
}
//Read the students
readData(studentFile, &database);
programInfo();
run(studentFile, &database);
}
Vielen Dank im Voraus für jede Hilfe!
Danke! Du hast recht, Ein Zeiger auf einen Zeiger. Danke dafür, immer noch ziemlich neu für C. Werde in Zukunft auf die Leute aufpassen! –