Caught by make mode=release.

Since file::file() did not open the file, file::~file() must not free it.

Use ::dup() so we operate on a clone.

Also based on prex code.

Various changes to fit into the OSv environment.  This also includes
a ramfs in-memory full filesystem.  Bootfs is rewritten as a simple
unpacker into ramfs, and the fs class is modified to wrap the VFS
instead of being an abstract subclass.

Usedful for implementing stdio.

Store directory entries in a hash table for future lookup.

We need one object, so we can use it as a key in the cache.  Store it in
the filesystem object.

It interferes with the upcoming cache lookup.  Use the existing metadata
instead to look for a directory.

real filesystems (and /proc, our immediate target) look up files incrementally
by each component.  Apply that to our filesystem infrastructure.

A new object is introduced, dir, representing a directory.  Lookup operations
are deferred to this object.

avoid leakage

It is not an exception condition.