It's not silent, you do declare that you want it released; you just do it before and it applies to all early returns. For example

    MUTEX_LOCK_GUARD(&lock)
        for (i = 0; i < n; i++)
            if (a[i] == x)
                return i;
    return -1;

Real world example here: https://github.com/qemu/qemu/blob/master/block/iscsi.c#L325

And the implementation: https://github.com/qemu/qemu/blob/master/include/qemu/lockab... (after inlining, the abstraction is completely zero cost).

> RAII is mostly already there

>> Releasing resources silently (other than the memory of automatic variables) is very un-C-like

The "R" is literally "resource", right? Sounds like instead of RAII you just meant unique_ptr.

Though I beg to differ on whether releasing memory automatically is any different from releasing other resources as far as being C-like is concerned!