Provenance of the 65536 Component Table limit

[baxter-huntington]

I have a burning question that I'd like to get to the bottom of. I have managed to run up against the following error when using WiX to package a large project:

wix.exe : error WIX7502: Maximum number of Components allowed in an MSI was exceeded. An MSI cannot contain more than 65536 Components.

I can see that these limits were added in this commit: wixtoolset/wix@15b9502

The established existence of this limit is further traced back to a comment in this thread from 20 years ago. To date, it still doesn't seem like Microsoft documents 65536, or any other hard limit, as the maximum number of components in an MSI. Now, I can absolutely see why there would be a limit for practical reasons—creating such a large MSI is probably ill-advised in most cases anyways—but I'm very curious if someone with much more knowledge of WiX/the Windows Installer API than I could point to the fundamental reason for this limitation. Is it as simple as a component count somewhere being stored as a 16-bit unsigned integer? Does the limit actually still exist?

I'll note that if I build WiX with the limit added in that commit removed, I can still generate a seemingly valid MSI, but Windows take ages to initialize the installer (enumerating the contents, perhaps?). Can't say whether it will reliably install, though.

Essentially, I'd like to re-open the discussion from that 20-year-old thread. Any and all insights would be much appreciated 😃

[wmanning]

This is the related issue: #702 and pull request wixtoolset/wix#186.