P0053R7 <syncstream>

[StephanTLavavej]

P0053R7 <syncstream>
P0753R2 osyncstream Manipulators

LWG-3127 basic_osyncstream::rdbuf needs a const_cast
LWG-3253 basic_syncbuf::basic_syncbuf() should not be explicit
LWG-3334 basic_osyncstream move assignment and destruction calls basic_syncbuf::emit() twice

Feature-test macro as of WG21-N4842, added by WG21-P1902:
#define __cpp_lib_syncbuf 201803L

[StephanTLavavej]

Qt reportedly macroizes emit so we will probably need push_macro defenses.

[MichaelRizkalla]

I am starting to work on P0053R7, just checking if I can pick it up since this is an entirely new header 🤔.
I have an initial basic_syncbuf's implementation in 30a999b,