<syncstream>: std::osyncstream memory leak

[segeter]

Problem Description:
Memory leak occurs when I use std::setw(32)。
Not sure if it's the same issue as #2763 and #2760

My test code：

Before the cycle starts：

Cycle after a while:

[segeter]

Track analysis, tips here：

[CaseyCarter]

Thanks for the report, @segeter - we'll determine if this is a duplicate or not and get a fix out as needed.

@fsb4000 do you want to take a look at this and determine if it's a duplicate? Feel free to say no and I'll investigate - I just thought I'd give you first right of refusal since you last touched this.

[fsb4000]

Sure, I will build against main and test it.

[fsb4000]

Yeah, it is not reproducible on main

(I'm showing "committed memory" instead of "working set" in the task manager)

[fsb4000]

and yes, on Visual Studio 2022 Professional 17.2.4, I also have the memory leak.

[CaseyCarter]

Thanks, @fsb4000! Looks like this is definitely a duplicate of #2760, the fix for which should ship in VS2022 17.4 preview 1.