This is meant to be a general place to list things that should be done "someday"

CXX Runtime Library Tasks
=========================
* Fix that CMake always link to /usr/lib/libc++abi.dylib on OS X.
* Look into mirroring libsupc++'s typeinfo vtable layout when libsupc++/libstdc++
  is used as the runtime library.
* Investigate and document interoperability between libc++ and libstdc++ on
  linux. Do this for every supported c++ runtime library.

Atomic Related Tasks
====================
* future should use <atomic> for synchronization.

Test Suite Tasks
================
* Improve the quality and portability of the locale test data.
* Convert failure tests to use Clang Verify.

Filesystem Tasks
================
* P0492r2 - Implement National body comments for Filesystem
    * INCOMPLETE - US 25: has_filename() is equivalent to just !empty()
    * INCOMPLETE - US 31: Everything is defined in terms of one implicit host system
    * INCOMPLETE - US 32: Meaning of 27.10.2.1 unclear
    * INCOMPLETE - US 33: Definition of canonical path problematic
    * INCOMPLETE - US 34: Are there attributes of a file that are not an aspect of the file system?
    * INCOMPLETE - US 35: What synchronization is required to avoid a file system race?
    * INCOMPLETE - US 36: Symbolic links themselves are attached to a directory via (hard) links
    * INCOMPLETE - US 37: The term “redundant current directory (dot) elements” is not defined
    * INCOMPLETE - US 38: Duplicates §17.3.16
    * INCOMPLETE - US 39: Remove note: Dot and dot-dot are not directories
    * INCOMPLETE - US 40: Not all directories have a parent.
    * INCOMPLETE - US 41: The term “parent directory” for a (non-directory) file is unusual
    * INCOMPLETE - US 42: Pathname resolution does not always resolve a symlink
    * INCOMPLETE - US 43: Concerns about encoded character types
    * INCOMPLETE - US 44: Definition of path in terms of a string requires leaky abstraction
    * INCOMPLETE - US 45: Generic format portability compromised by unspecified root-name
    * INCOMPLETE - US 46: filename can be empty so productions for relative-path are redundant
    * INCOMPLETE - US 47: “.” and “..” already match the name production
    * INCOMPLETE - US 48: Multiple separators are often meaningful in a root-name
    * INCOMPLETE - US 49: What does “method of conversion method” mean?
    * INCOMPLETE - US 50: 27.10.8.1 ¶ 1.4 largely redundant with ¶ 1.3
    * INCOMPLETE - US 51: Failing to add / when appending empty string prevents useful apps
    * INCOMPLETE - US 52: remove_filename() postcondition is not by itself a definition
    * INCOMPLETE - US 53: remove_filename()'s name does not correspond to its behavior
    * INCOMPLETE - US 54: remove_filename() is broken
    * INCOMPLETE - US 55: replace_extension()'s use of path as parameter is inappropriate
    * INCOMPLETE - US 56: Remove replace_extension()'s conditional addition of period
    * INCOMPLETE - US 57: On Windows, absolute paths will sort in among relative paths
    * INCOMPLETE - US 58: parent_path() behavior for root paths is useless
    * INCOMPLETE - US 59: filename() returning path for single path components is bizarre
    * INCOMPLETE - US 60: path("/foo/").filename()==path(".") is surprising
    * INCOMPLETE - US 61: Leading dots in filename() should not begin an extension
    * INCOMPLETE - US 62: It is important that stem()+extension()==filename()
    * INCOMPLETE - US 63: lexically_normal() inconsistently treats trailing "/" but not "/.." as directory
    * INCOMPLETE - US 73, CA 2: root-name is effectively implementation defined
    * INCOMPLETE - US 74, CA 3: The term “pathname” is ambiguous in some contexts
    * INCOMPLETE - US 75, CA 4: Extra flag in path constructors is needed
    * INCOMPLETE - US 76, CA 5: root-name definition is over-specified.
    * INCOMPLETE - US 77, CA 6: operator/ and other appends not useful if arg has root-name
    * INCOMPLETE - US 78, CA 7: Member absolute() in 27.10.4.1 is overspecified for non-POSIX-like O/S
    * INCOMPLETE - US 79, CA 8: Some operation functions are overspecified for implementation-defined file types
    * INCOMPLETE - US 185: Fold error_code and non-error_code signatures into one signature
    * INCOMPLETE - FI 14: directory_entry comparisons are members
    * INCOMPLETE - Late 36: permissions() error_code overload should be noexcept
    * INCOMPLETE - Late 37: permissions() actions should be separate parameter
    * INCOMPLETE - Late 42: resize_file() Postcondition missing argument

Misc Tasks
==========
* Find all sequences of >2 underscores and eradicate them.
* run clang-tidy on libc++
* Document the "conditionally-supported" bits of libc++
* Look at basic_string's move assignment operator, re LWG 2063 and POCMA
* Put a static_assert in std::allocator to deny const/volatile types (LWG 2447)