code --prof-startup fails to profile renderer and exthost

[MarkZuber]

Does this issue occur when all extensions are disabled?: Yes/No

• VS Code Version: 1.91 -> 1.100
• OS Version: macos / windows

Steps to Reproduce:

1. run: 'code --prof-startup'
   FAILED to start profiling for 'renderer' on port '23680'
   FAILED to start profiling for 'extHost' on port '23681'

2. vscode launches. there is a main.cpuprofile.txt in $HOME -> ~/prof-9Ol7MjGb.main.cpuprofile.txt

3. dialog comes up for "create issue and restart" or "restart"

4. click on "restart"

5. vscode is relaunched but never comes up, requires a force quit / klil

I've tried this with :
latest insiders
--disable-extensions
macos and windows on multiple machines
v1.91 and v1.100 to test if regression

also hacked the code and rebuilt to print the err variable at failure and it only says "failed to connect":
FAILED to start profiling for 'extHost' on port '20795' -> Error: failed to connect

[DanTup]

I'm hitting the same on Windows, trying to profile the startup of my extension:

PS D:\Dev\Test Projects\flutter_counter> code --prof-startup
FAILED to start profiling for 'renderer' on port '39821'
FAILED to start profiling for 'extHost' on port '39822'

I updated the line that logs this to include the error:

console.error(`FAILED to start profiling for '${name}' on port '${opts.port}: ${err}'`);

However I've been unable to get Code to launch from source with --prof-startup working. I tried both --prof-startup and --prof-startup-prefix in the launch.json, but even if I create a random file to prevent errors about it not existing, it doesn't seem to actually start any profiling.

[DanTup]

I managed to get it to work with code-cli.bat, but unfortunately the error wasn't much more useful:

FAILED to start profiling for 'renderer' on port '8802: Error: failed to connect'
FAILED to start profiling for 'extHost' on port '8803: Error: failed to connect'