Kirk Shoop kirkshoop

ABI Design Notes

Author: Kirk Shoop

feature	description
link-time replaceable	Allows the std library to know at link-time which services to construct. Allows specified construction order of services by the std library. Prevents any need to address the complexities of runtime replacement in the specification or in the implementation (eg. when to construct, when to destruct, how many replacements allowed, etc..)
cannonical across all stdlib implementations	libraries like TBB and Qt implement a replacement once and that works with all std libraries.
user providedstorage	minimize allocations by allowing a user to supply storage for an operation

feature	description
link-time replaceable	Allows the std library to know at link-time which services to construct. Allows specified construction order of services by the std library. When the order is specified, this enables deterministic reasoning about dependencies for users and replacement implementations. Prevents any need to address the complexities of runtime replacement in the specification or in the implementation (eg. when to construct, when to destruct, how many replacements allowed, when are replacements allowed, what happens when an invalid replacement is attempted, etc..).
cannonical across all stdlib implementations	libraries like TBB and Qt implement a replacement once and that works with all std libraries.
user provided storage	minimize allocations by allowing a user to supply storage for an operation
user provided allocator	Allows the user to determine how operations allocate additional storage
asynchronous

	/*
	* Copyright (c) Facebook, Inc. and its affiliates.
	*
	* Licensed under the Apache License, Version 2.0 (the "License");
	* you may not use this file except in compliance with the License.
	* You may obtain a copy of the License at
	*
	* http://www.apache.org/licenses/LICENSE-2.0
	*
	* Unless required by applicable law or agreed to in writing, software

	// async_scope has a single concern - it provides a scope in which senders
	// can be spawned without waiting for each sender to complete.
	// async_scope is intended to compose inside of non-blocking operations
	// (none of it's methods are allowed to block).
	//
	// Requirements:
	//
	// - async_scope must be empty when the destructor runs.
	// - senders passed to spawn must not require any CPOs on the receiver
	// connected to them.


	struct prefix_scheduler_fn {
	template<typename Predecessor>
	struct _sender : ex::sender_base {
	Predecessor p_;
	template <std::execution::receiver_of R>
	friend auto tag_invoke(ex::connect_t, _sender, R&& rec){
	auto prefix = p_ \|
	ex::let_value(
	[sched = ex::get_scheduler(rec)](auto&&... vn){

	/*
	* Copyright 2019-present Facebook, Inc.
	*
	* Licensed under the Apache License, Version 2.0 (the "License");
	* you may not use this file except in compliance with the License.
	* You may obtain a copy of the License at
	*
	* http://www.apache.org/licenses/LICENSE-2.0
	*
	* Unless required by applicable law or agreed to in writing, software

	/*
	* Copyright 2019-present Facebook, Inc.
	*
	* Licensed under the Apache License, Version 2.0 (the "License");
	* you may not use this file except in compliance with the License.
	* You may obtain a copy of the License at
	*
	* http://www.apache.org/licenses/LICENSE-2.0
	*
	* Unless required by applicable law or agreed to in writing, software

	# 1 "<built-in>"
	# 1 "/Users/kirk/source/wg21_p2300_std_execution/examples/hello_world.cpp"
	/*
	* Copyright (c) NVIDIA
	*
	* Licensed under the Apache License Version 2.0 with LLVM Exceptions
	* (the "License"); you may not use this file except in compliance with
	* the License. You may obtain a copy of the License at
	*
	* https://llvm.org/LICENSE.txt

	package wasi:[email protected];
	/// WASI Context is an execution context intended to allow users to
	/// schedule async functions onto a context provided by the system.
	///
	/// It is intended to be portable across platforms
	/// It is intended to support zero-allocation scheduling
	/// It is intended to abstract users from threads and locks
	///
	interface context {
	use wasi:[email protected].{scheduler};