Why is Universal CRT required?

[jay]

I can see that last year CRT dependency was switched to from msvcrt to Universal, why? I'm using an old Windows 7 VM snapshot and I had to download the Universal CRT to it when I saw a cryptic error about curl not starting due to a missing dll. Not a problem but I wasn't expecting that.

Edit: I did not have this problem in a more recent Windows 7 VM snapshot. The update was already included, presumably by Windows Update.

[vszakats]

• Legacy msvcrt is a piece of code that hasn't seen an update or bugfix in many years. It's abandoned/unmaintained code. It also had accumulated unfixed bugs/vulnerabilities. Though even without the latter, relying on abandoned components I feel is best to avoid.
  According to MS ^{1 2}, on Windows 7 UCRT was supposed to get installed via Windows Update. I haven't double-checked their claims, and cannot tell why it wasn't present on your system. Either way it can be installed via an official update package (also for Vista).

• UCRT is required for ARM64 builds.

• Using UCRT for ARM64 while keeping msvcrt for Intel is overly complex and error-prone.

Footnotes

1. https://learn.microsoft.com/en-us/cpp/porting/upgrade-your-code-to-the-universal-crt?view=msvc-170#deployment-and-redistribution-of-the-universal-crt ↩

2. https://learn.microsoft.com/en-us/cpp/windows/universal-crt-deployment?view=msvc-170 ↩