As far as I am aware, they never work that great on UNIX compilers, as no big effort was ever spent improving them.
About 20 years ago, on UNIX workloads we used to speed the compilation via ClearMake, a kind of distributed version of code cache that would plug into the compilers, however it has part of ClearCase SCM product.
On Windows, with Microsoft and Borland (nowadays Embarcadero), they work quite alright.
Also, modules will fix that, as per VC++ reports, importing the whole standard library (import std, as per C++23) takes a fraction of only including iostream.
About 20 years ago, on UNIX workloads we used to speed the compilation via ClearMake, a kind of distributed version of code cache that would plug into the compilers, however it has part of ClearCase SCM product.
On Windows, with Microsoft and Borland (nowadays Embarcadero), they work quite alright.
Also, modules will fix that, as per VC++ reports, importing the whole standard library (import std, as per C++23) takes a fraction of only including iostream.