Re: master 2c79a8f 2/2: Use posix_spawn if possible.

[Eli Zaretskii <eliz@gnu.org>]

> Date: Tue, 25 Jan 2022 10:58:51 +0200
> Cc: p.stephani2@gmail.com, alan@idiocy.org, mituharu@math.s.chiba-u.ac.jp
> From: Saulius Menkevicius <sauliusmenkevicius@fastmail.com>
> 
> Sorry I did not mention the platform, this happens on Linux/x64 and has 
> been reported by multiple persons:
> 
> - https://github.com/razzmatazz/csharp-language-server/issues/12
> 
> 
> The issue has been noticed when dotnet-based LSP servers are used with 
> emacs/lsp-mode, -- in particular lsp-mode starts the server using 
> `make-process` and then communicates over stdio. Link to the code that 
> launches the server:
> 
> - https://github.com/emacs-lsp/lsp-mode/blob/master/lsp-mode.el#L6925
> 
> 
> We have csharp-ls and fsac servers launched with the same mechanism as 
> are for other languages -- which are working ok with posix_spawn 
> enabled. It only breaks for those before-mentioned LSP servers that are 
> implemented on top of dotnet and use dotnet runtime (same thing as JVM, 
> but for C#/F#/CLR languages).
> 
> Now it appears, that switch to posix_spawn broke communication over 
> stdio to those dotnet-based LSP servers for some technical reason, -- I 
> didn't investigate yet why, because it is a bit over my head. I *think* 
> there is an interplay between posix_spawn-based process launch 
> implementation in emacs and dotnet runtime stdio abstractions/platform 
> layer -- because otherwise other language servers work with that commit 
> that enables posix_spawn, like those based on JVM too.

What is special about dotnet's runtime stdio usage?