Mysterious freeing

[Jonathan]

I just got something really strange, regardless of optimization. I already deleted my code because it was messy and I wanted to do it over again anyway, so you can't have a look at it, but the allocation part was basically:

Code: Select all

struct somestruct {
    void *pointer;
};

struct somestruct function() {
    struct somestruct ret;
    ret.pointer = malloc(123);
    // check after alloc
    printf("pointer=%p\n", ret.pointer);
    printf("size=%u\n", malloc_size(ret.pointer));
    bzero(ret.pointer, 123); // do something with the memory
    // check before return
    printf("pointer=%p\n", ret.pointer);
    printf("size=%u\n", malloc_size(ret.pointer));
    return ret;
}

void anotherfunc() {
    struct somestruct ret = function();
    // final check
    printf("pointer=%p\n", ret.pointer);
    printf("size=%u\n", malloc_size(ret.pointer));
}

It would print something like:

Code: Select all

pointer=0x2008000
size=4096
pointer=0x2008000
size=4096
pointer=0x2008000
size=0

and crash when referencing the memory.

Any idea what could be happening?

[Jonathan]

I got the rewrite done and it's working fine (and several orders of magnitude faster, even without optimizer!), but I'm still wondering what could have caused it.

[Lucifer]

Looks like, for some reason, your struct went out of scope, although I can't see why that would happen.

[Jonathan]

It didn't (out of scope means you can't reach it, but I can), and why would it free something inside the struct?