TODO

- PLANNED FOR AFTER DMTCP-1.2.4 (as time and resources permit):
  1. Create MTCP ckpt module making it easy to choose the preferred
	compression routine on fly, remote checkpoints, etc.
  2. Modify ckpt image format to note zero-mapped pages and use
     /proc/*/pagemap.
	(An intermediate solution to replace runs of zeros
	 by a region of zero-mapped pages at checkpoint time has already
	 been implemented as of DMTCP-1.2.4.)
  3. Replace temporary files of $DMTCP_TMPDIR (created on restart)
	by shared memory objects.
  4. Faster checkpoint/restart:  Don't remap libs
  5. ELF honors a segment of type PT_LOAD.  This can be used in the future
	to reserve address ranges to prevent conflicts with vdso, etc.
	This will aid process migration between different Linux kernels,
	by stopping a loader using address space randomization from
	placing vdso, etc., in the wrong place.
  6. dmtcp_launch --disable-randomization   should be implemented,
        which would also disable randomization on restart.
        This can be useful for internal testing and further development,
	but also useful for users with specialized needs.  Note that
	gdb disables randomization of the target process by default starting
	in GDB 7.x.

- When environ is not yet initialized, currently libdmtcp.so simply returns.
  (This occurs when executing libc.so.6 .)
  We should spend more effort to find environ at top of stack.
  Note that bash also plays tricks with environ, but bash still gives
    us a working getenv().

- We currently wrap fork(), but not vfork().  Usually, the exec happens
  soon after vfork().  But if we checkpoint after vfork() and before
  exec, then we would miss the child process.  This should be fixed.

- setsighandler fails if user has reset our signal handler
  Do we cleanly tell the user what signal is being used by app,
  and to rerun dmtcp with --sigckpt  set to other signal?

- Extend list of syscalls using netdb to put wrappers around them.
  The danger is that in invoking the netdb, they might want to
  create a socket.  Then we detect this, and we try to create
  a socket to the coordinator.  This hits our wrapper function, which
  then creates an infinite loop.  At least, we think we saw this in
  Ubuntu 6.06 (dapper).
          
- Many more exotic fcntl()/ioctl() flags are not checkpointed

- dmtcp_coordinator should refuse to allow other users to connect to it.
  (Are there security issues with respect to spoofing, also?)

- Tab completion fails on tcsh. (?)

- dmtcp_launch a.out > a.txt ; restart fails if a.txt not found.

- Add support for epoll_pwait() and ppoll().

- If reading from stdin, maybe we should drain the stdin buffer first before
  checkpointing, so we can restart without losing user input.  Or maybe
  it's better if dmtcp does this.

Memory maps:
- Should save only used part of stack, and document this in DOC.
  At least do this in x86_64 case, where stack is larger?

- __i386__:
  Right after heap, in address space of libraries, comes something of size
  0x1000 with no read-write-exec permission, and then something of size:
  0x801000
  That's almost 10 MB.  What's it for?  Do we need to checkpoint it?

PID-VIRTUALIZATION:
1. wait status of zombie processes
     Store status of those processes which were zombie at checkpoint time. If
     the parent process does a wait() system call for that child after restart
     we should return its status.
2. update dmtcp_restart.cpp to check and restore orphaned child processes at
  restart.
3. better error handling for missing processes.

REPLACE all temporary files present in $DMTCP_TMPDIR with some sort of
shared-memory files.

SOCKETS:
1. A process calls socket(), then forks a child process. The child then calls
   connect(). If the parent process were to save/restore socket, the parent
   will just create the socket and not do the connect() on restart.

LD_PRELOAD:
1. Better error message when launching a 32-bit binary under a 64-bit system
   without 32-bit plugin libraries.