A few things off the top of my head, influenced by both trying to build Rust code for the Linux kernel as a hobby and maintaining compilers in my day job: - GC

A few things off the top of my head, influenced by both trying to build Rust code for the Linux kernel as a hobby and maintaining compilers in my day job: - GCC still supports more architectures/platforms than LLVM does. Apart from various rare/obscure/embedded platforms, one notable one (I think) is x86-16: .code16gcc pretty much works, LLVM only kinda supports it. - GCC has its own plugin interface. If you already have GCC plugins, you probably want to stick with GCC. - If you have a large legacy codebase that's probably got some UB somewhere because that's the nature of having large codebases written by fallible humans, it's probably less likely that a new versions of the same compiler will misinterpret your intentions than a new compiler would. (But this is a weak argument, since new versions could still change their interpretation/behavior.)