[bobmcnamara]

IAR has their own backend and I believe front-end as well.

They routinely smoked GCC and Clang, and sometimes ARMs tools on a variety of tasks.

I'm not sure I see the advantage on Qt owning a compiler though - one of Qt's strengths is portability.

[bluGill]

The advatage might be they can ensure the compiler supports the new features qt wants to use.

reflection could replace moc, (likely c++29 needed) but if compilers don't implement that part of reflection qt can't use it. If qt can get compilers updated that helps them.

[maleldil]

Relevant link regarding Qt moc and reflection https://wiki.qt.io/C%2B%2B_reflection_(P2996)_and_moc