advanced patterns When Using `qsort` with Struct Array in C
I'm getting frustrated with This might be a silly question, but I'm working with an scenario with the `qsort` function from the C standard library when sorting an array of structs. I have a struct called `Person` that contains a name (string) and an age (integer). When I try to sort an array of `Person` by age, it doesn't seem to sort correctly. Here's the code I'm using: ```c #include <stdio.h> #include <stdlib.h> #include <string.h> typedef struct { char name[50]; int age; } Person; int compare(const void *a, const void *b) { Person *personA = (Person *)a; Person *personB = (Person *)b; return personA->age - personB->age; } int main() { Person people[] = { {"Alice", 30}, {"Bob", 25}, {"Charlie", 35}, {"Diana", 28} }; size_t size = sizeof(people) / sizeof(people[0]); qsort(people, size, sizeof(Person), compare); for (size_t i = 0; i < size; ++i) { printf("%s: %d\n", people[i].name, people[i].age); } return 0; } ``` When I run this code, the output is: ``` Alice: 30 Bob: 25 Charlie: 35 Diana: 28 ``` It seems the array is not sorted by age as expected. I've also tried different approaches like returning `personB->age - personA->age` in the `compare` function, but that only changes the order slightly without providing the correct sorting. I am compiling with `gcc 11.2` on Linux. Can someone guide to understand what I'm doing wrong? Are there any edge cases or considerations I should be aware of when using `qsort` with structs? I'm working on a application that needs to handle this. What's the best practice here? I'm working on a API that needs to handle this. This is happening in both development and production on CentOS. Cheers for any assistance!