https://en.wikipedia.org/wiki/EPOC_(operating_system)
Symbian C++ had a couple of issues, namely several restrictions of accomodating C++ for a microkernel, before the days of C++98, and organically growing from there.
So there were several idioms and restrictions on how the language could be used, and the toolchain went through several iterations, MS-DOS batch files, Perl scripts, Metrowerks based compiler, eventually replaced by an Eclipse based IDE (after a false start), Carbide.
Qt came later into the picture as Symbian was being modernized, and after a POSIX compatibility layer (PIPS) was added into the platform.
You had the security rules that iOS "invented", C++, Java and Python toolchains, being able to run http server on the phone, 3D support for C++ and Java applications.
But Symbian C++ was a bit of a pain (see link below), it was being modernized via PIPS and Qt (as mentioned), but then Elop came to Nokia, the famous burning platforms memo came out, and everyone went away.
Nokia development culture was pretty much anti-MS, so most went elsewere, instead of bothering with Windows Phone 7.
http://symbian.tomuta.ro/GUID-C3206E31-251C-4AFC-90C2-04B38C...