One of the core ideas of working with LTS is that you can build your software on an LTS release and ship it to somebody else on the same LTS release, either as a source or as a binary.
If you want the latest GCC, that's fine, you're not forced to use the default compiler distributed with your OS. But it doesn't make sense to update the default compiler used in an LTS release. If you want that, then you don't want LTS.
If you want to develop an application, you use your own toolchain. But yes I know most C++ people don't d this because C++ tools don't easily support it. But that's on C++ for not having pyenv, rustup, multiruby, etc equivalent.
This needs to be emphasized.
Yes, and updating compilers don't prevent that at all. You can use GCC 10 to ship code that will build and run on Ubuntu 12.04 without issues. Xcode 11 can ship code that works back to macOS 10.6 and Visual Studio 2019 can still optionally target windows fucking XP !
This is incorrect. In practice, for larger code bases, upgrading to a newer version of GCC or Clang is something that must be done purposefully, and you must test.
Sometimes it turns out that your code relies on some compiler behavior which has changed. Sometimes newer compilers are stricter than older compilers. There are plenty of real-world cases of these problems!
> Xcode 11 can ship code that works back to macOS 10.6 [...]
There are a number of features that are specific to the macOS toolchain which make this possible. Take a look at the "-mmacosx-version-min" flag on the macOS compiler. This selectively enables and disables various APIs. These features don't solve all the compatibility problems, either.
> Visual Studio 2019 can still optionally target windows fucking XP !
We're talking about Linux here. The Windows toolchain is radically different.
You do understand that ABI backward compabitility is not ensured, don't you?
https://gcc.gnu.org/onlinedocs/libstdc++/manual/abi.html
Some software packages even break between distro releases.
The primary value of a distro is to provide a fixed platform that application developers and users can safely target. Risking ABI breakups just because a rare number of users wish to be on the bleeding edge without wanting to do any of the work to install their own software is something that's very hard to justify.
