Memory allocation and freeing not working-CodePudding

I'm trying to create dynamically allocated array of structures in C (VS 2022) but the program keeeps crashing while freeing the memory with problem:

Unhandled exception at 0x00007FF9261ECF5D (ntdll.dll) in t3.exe: A LIST_ENTRY has been corrupted (i.e. double remove).

Code:

void task() {
    int i, j, size = 32;
    struct Student tmp;
    struct Student * students = (struct Student*)malloc(size*sizeof(students));
    for (i = 0; i < size; i  ) {
        scanf(" %s", &students[i].name);
        scanf(" %s", &students[i].lastname);
        scanf(" %d", &students[i].index);
        scanf(" %s", &students[i].major);
        scanf(" %d", &students[i].semester);
        scanf(" %d", &students[i].grp);
    }
    free(students);
}

Should I also allocate every struct element manually in for loop right after getting input and then free it the same way?

CodePudding user response：

You should malloc(sizeof(struct Student) instead of students which is just a size of pointer.

CodePudding user response：

sizeof( students ) in this declaration

struct Student * students = (struct Student*)malloc(size*sizeof(students));

is equivalent to sizeof( struct Student * ). But you need to use sizeof( struct Student ) or sizeof( *students ) because you need to allocate an array of objects of the type struct Student.

Also these calls of scanf

scanf(" %s", &students[i].name);
scanf(" %s", &students[i].lastname);
scanf(" %s", &students[i].major);

you need to rewrite at least like

scanf(" %s", students[i].name);
scanf(" %s", students[i].lastname);
scanf(" %s", students[i].major);

If the data member major has the type char then you need to write

scanf(" %c", &students[i].major);

Also name and lastname (and major if it does not have the type char) must ne chracater arrays.

CodePudding user response：

replace

struct Student * students = (struct Student*)malloc(size*sizeof(students));

with

struct Student * students = (struct Student*)malloc(size*sizeof(struct Student));

Also since you are using a pointer you would need to reference the variables with ->