[API Proposal]: Interlocked.[Compare]Exchange for bool

[colejohnson66]

Background and motivation

Many times, I've found myself wanting to use Interlocked.Exchange on a single boolean flag. However, this is not possible, and I'm forced to use an int with a zero or one.

An API discrepancy exists where Volatile.Read and Volatile.Write with bool exist, but none for Interlocked.

Following #64658, bool overloads should be added.

Theoretically, these can be implemented as wrappers around existing Interlocked.[Compare]Exchange through Unsafe.As.

API Proposal

namespace System.Threading;

public static class Interlocked
{
    public static bool CompareExchange(ref bool location, bool value, bool comparand);
    public static bool Exchange(ref bool location, bool value);
}

API Usage

Old code:

if (Interlocked.Exchange(ref _interlock, 1) == 1)
    return; // some other thread got here before us
// do stuff
Volatile.Write(ref _interlock, 0);

New code:

if (Interlocked.Exchange(ref _interlock, true))
    return; // some other thread got here before us
// do stuff
Volatile.Write(ref _interlock, false); // already existing API since .NET 4.5

Alternative Designs

No response

Risks

None.

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[jkotas]

The bool overload was discussed and rejected in #64658 (comment)

[colejohnson66]

Unless I'm missing something, I don't see a rejection anywhere. Just that users using Unsafe.As<byte,bool> (and vice versa) themselves is dangerous. Any non-zero backed boolean is True, but comparison is done bitwise. Specifically, Stephen Toub said that he "[doesn't] particularly care whether we add a bool-based overload, [...]"

[colejohnson66]

Duplicate of #65184?