vNext Planning

Salvage The Old vNext Branch

• Multithreading overhaul
• Iterator debugging overhaul (doubly-linked iterator chains, no proxy allocations)
  • Still need to overhaul deque and vector<bool>
  • Also simplifies checked/unchecked and modifiable/const, avoiding inheritance (which is non-standard)
• Remove /clr:pure
• Flat C exports
• Remove <hash_map>, <hash_set>
• Remove tr1
• Other changes? (vcplatform?)

Major Overhauls

• <regex>
• <deque>
• <unordered_map>, <unordered_set>
• iostreams floating-point

More Work

• vNext Issues
  • #938 P0408R7 Efficient Access To basic_stringbuf's Buffer can be significantly simplified
• TRANSITION, ABI comments
• Consolidate satellite DLL and import LIB code back into the main DLL (and API loading code like for ICU); make sure to keep vector/string etc. out of the DLL/import LIB.
• Drop Vista support; Win7 must be the minimum platform
• Remove _app DLLs
• Increase x86 to /arch:SSE2?
• <variant> changes:
  • Store index() + 1 instead of index() to so the range of possible stored values is contiguous for minor codegen improvements.
  • The hash value of a variant should depend on its index() as well as the stored value so variant<int, int>{in_place_index<0>, 42} and variant<int, int>{in_place_index<1>, 42} don't collide.
• [[no_unique_address]] will be unconditionally available, allowing us to replace _Compressed_pair and improve the representations of more types.

Compiler Work

• Remove /Za (effectively superseded by /permissive-)
• Remove /Zc:wchar_t-
• Increase minimum Standard version to C++17 or C++20?
• RTTI overhaul?
• EH overhaul possible? (Table-based x86?)
• Fix Empty Base Class Optimization
• Avoid ABI-breaking options (e.g. /vd2, /vmg, /J)
• How do we detect/prevent mixing?