You're right that compilers tend to have bugs, but in practice, compiler bugs are rarely the cause of software issues. The same cannot be said of libraries. Major SSL/TLS libraries for instance tend to be written in C, and all of them have had memory-safety bugs.

> Library authors know things about what their code is meant to be doing that compilers cannot deduce, so cannot act on. But the library author can.

I don't see your point here.

> A library, according to how heavily it is used, benefits from more thorough testing than generic application code gets

This doesn't generalise. There's plenty of very widely used application-specific code, and there's plenty of little used library code. Also, widespread use does not imply a high level of scrutiny, even if we're talking only about Free and Open Source software.

Anyway, that's all a sidetrack. The benefits of memory-safe languages aren't up for debate, even for well-scrutinised codebases. We continue to suffer a stream of serious security vulnerabilities arising from memory-safety issues in code written in unsafe languages. The go-to example is Chromium, where 70% of serious security issues are due to memory safety. [0]

[0] https://www.chromium.org/Home/chromium-security/memory-safet...