strcpy()/strncpy() crashes on structure member with extra space when optimization is turned on on Unix?

Question

When writing a project, I ran into a strange issue.

This is the minimal code I managed to write to recreate the issue. I am intentionally storing an actual string in the

Answer 1

Your pointer p->c is the cause of crash.
First initialize struct with size of "unsigned long long" plus size of "*p".
Second initialize pointer p->c with the required area size. Make operation copy: strcpy(p->c, str);
Finally free first free(p->c) and free(p).
I think it was this.
[EDIT]
I'll insist. The cause of the error is that its structure only reserves space for the pointer but does not allocate the pointer to contain the data that will be copied.
Take a look

int main() 
{
    pack *p;
    char str[1024];
    gets(str);
    size_t len_struc = sizeof(*p) + sizeof(unsigned long long);
    p = malloc(len_struc);
    p->c = malloc(strlen(str));
    strcpy(p->c, str); // This do not crashes!
    puts(&p->c);
    free(p->c);
    free(p);
    return 0;
}

[EDIT2]
This is not a traditional way to store data but this works:

    pack2 *p;
    char str[9] = "aaaaaaaa"; // Input
    size_t len = sizeof(pack) + (strlen(str) + 1);
    p = malloc(len);
    // Version 1: crash
    strcpy((char*)p + sizeof(pack), str);
    free(p);