Inconsistent Behavior When Using `malloc` with `sizeof` for Structs and Arrays in C
I'm writing unit tests and I'm encountering inconsistent behavior when allocating memory for a struct that contains an array in C... The struct is defined as follows: ```c typedef struct { int id; char name[50]; } Person; typedef struct { Person *members; size_t count; } Group; ``` When I try to allocate memory for the `members` array dynamically, I use the following code: ```c Group group; group.count = 5; group.members = (Person *)malloc(group.count * sizeof(Person)); ``` This works fine, and I can add members to the group. However, when I try to print out the members' names after allocating the memory, I sometimes get garbage values or even a segmentation fault. I've also tried initializing the `members` array using the following code: ```c for (size_t i = 0; i < group.count; i++) { group.members[i].id = i; snprintf(group.members[i].name, sizeof(group.members[i].name), "Person %zu", i); } ``` This results in correctly formatted output most of the time, but occasionally, when I try to access `group.members[i]`, it leads to a segmentation fault if `i` exceeds the allocated count. I suspect there might be an issue with memory allocation or accessing memory out of bounds. I've verified that `group.count` is set correctly before allocating memory, but I also noticed that if I allocate memory without `sizeof(Person)` like this: ```c group.members = (Person *)malloc(group.count * sizeof(char[50])); ``` I get a compile-time warning, but I thought it might be worth a try since I only needed the size of the name array. If I run this, I see unpredictable behavior when accessing `group.members` later. Could anyone explain why I'm experiencing these inconsistencies? Is it related to how I'm allocating memory or initializing the structs? What is the best practice here to avoid such issues? Thanks in advance! I'm developing on macOS with C.