In Amalloc() we do this:

    debug_only(if (UseMallocOnly) return malloc(x);)

so, if and only if DEBUG is on do we use malloc().

However, the matching free() in ResourceArea::rollback_to() does not have a matching debug_only guard:

    if (UseMallocOnly) {
        free_malloced_objects ...

UseMallocOnly is a product flag. So, if PRODUCT is true, and DEBUG is true, we have a mismatched malloc() and free(). This is undefined behaviour.

I suggest we should remove the debug_only guard.