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Comment by userbinator | Hacker News Reader

...and absurdly complex.

One of the quick tests I like to do to ascertain the complexity of a codebase is "how long does it take to find the entrypoint" and "how long does it take to find the core functionality"?

In this case, I have been clicking around through nearly empty directories for 15+ minutes and haven't seen anything that looks like an entrypoint yet, nevermind the main loop.

In contrast, I downloaded the Bash source and within 5 minutes found the main loop (eval.c) and entrypoint (shell.c).

Now I'm curious to know what the cmd.exe source is like, but MS seems to have no intention of releasing that.

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I did the same exercise, and I found this immediately (straight drilldown through directories from the top level):

https://github.com/PowerShell/PowerShell/blob/master/src/pow...

It's instantiating the execution engine (.NET-speak for the core runtime) getting ready to run Monad (the original codename for PowerShell).

I think part of it is familiarity and context. I knew none of the command bits would be likely to contain an entrypoint. Directories that mentioned native looked useful for finding an entrypoint, because I know that PowerShell is implemented in C# - I reasoned I'd be able to find further managed entrypoints by looking at where it starts out in C++.

You can see that the main object it instantiates is Microsoft.PowerShell.UnmanagedPSEntry. Looks useful.

A search across the repo for UnmanagedPSEntry lead me to https://github.com/PowerShell/PowerShell/tree/master/src/Mic... which seems to contain all the entrypoints you're looking for.

The main loop is in InputLoop in https://github.com/PowerShell/PowerShell/blob/master/src/Mic...

(FTR, this took me about 8 minutes, including finding links that didn't include hashes.)

Some hand-wavily relevant comments:

- I had the exact same problem - "how do I get at the entrypoint and follow this" - only earlier today, with Chromium. I was trying to figure out why sync was broken and thought I'd try and follow the (C++) breadcrumbs. It didn't go very well. https://bugs.chromium.org/p/chromium/issues/detail?id=671498

- AFAIK, cmd.exe is basically a horrible, horrible hack. I'm not 100% sure, but I think an instance of cmd.exe is the only way you can run things with a stdout, as in Windows has no concept of TTYs - the cmd.exe process uses a bunch of undocumented kernel interface APIs to "make it work™". Related: https://github.com/Microsoft/BashOnWindows/issues/111#issuec...

Edit/Update: PSA, if you use a sync passphrase with Chrome your history from other devices doesn't show up in chrome://history. Known bug, will hopefully be rearchitected long-term.

I have to say though, the writeup on that Chromium ticket I filed was absolutely awesome. Did someone here notice...? :P

After clicking that github link, it appears to be in `src/powershell/Program.cs`, along with a readme explaining how the entrypoint works.

I'm not making any statement on the complexity of the general Powershell codebase, but finding the entrypoint at least seems straightforward.

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