JTC 1/SC 22/WG 23 C++ Vulnerability Discussions    WG 23 N1508
		September 18 2025

Participants
    Stephen Michell - convenor, SCC
    Richard Corden - USA
    Erhard Ploedereder - liaison
    Paul Preney - Canada
    Peter Sommerlad

 Regrets
    Matt Butler - USA
    Loic Joly - AFNOR

    
Actions:

Scheduled meeting 1 Sep 2025 was cancelled.

Welcome back to Peter!

Issues addressed

Clause 7.5 Coroutines
   Provided an initial writeup of coroutines by Paul. Group editing. Significant more needed.
   Paul to restructure as
     1) using coroutines defined in library environments
     2) roll-your-own coroutines.

Paul will separate the clause 7 material into separate files for better control.

Issue XXX

FROM THE CHAT 2025-09-15:

10:27:27 From Peter Sommerlad to Everyone:
	[\[EWF\]](#EWF)
	
11:27:36 From Peter Sommerlad to Everyone:
	The coroutine promise_type (as given by std::coroutine_traits<Result>::promise_type) is distinct from std::promise
	
11:33:23 From Paul Preney to Everyone:
	Section 17.2 Coroutines [support.coroutine]
	
11:33:33 From Paul Preney to Everyone:
	in C++23
	
11:50:48 From Peter Sommerlad to Everyone:
	tmp = obtain_value();
	
11:50:58 From Peter Sommerlad to Everyone:
	int obtain_value(){
	
11:51:26 From Peter Sommerlad to Everyone:
	std::scoped_lock lg{m}; return i;
	
12:02:54 From Stephen Michell to Everyone:
	```{.cpp}
	std::mutex m;
	int i = 42;
	// ...
	std::generator<int> bar()
	{
	    std::unique_lock lk{m};
	    auto const tmp{i};          // make a copy
	    lk.unlock();                // release the lock
	    co_yield tmp;               // yield the copy with no locks held
	}
	```
	
12:04:36 From Peter Sommerlad to Everyone:
	```{.cpp}
	std::mutex m;
	int i = 42;
	// ...
	int bar_impl(){
	  std::scoped_lock lk{m};
	  return i;
	}
	std::generator<int> bar()
	{
	    co_yield bar_impl();               // yield a copy with no locks held
	}
	```