Proc macros must not be compiled with -Ztls-model=initial-exec as -Ztls-model=initial-exec is incompatible with dlopen. Glibc is somewhat lenient with dlopening dylibs compiled with -Ztls-model=initial-exec for as long as there is room, but other libc implementations may not provide enough room or provide room at all. For example on FreeBSD trying to use rustc_driver results in the following error:

https://cirrus-ci.com/task/4557776715776000

error: /.rustup/toolchains/nightly-2024-12-28-x86_64-unknown-freebsd/lib/rustlib/x86_64-unknown-freebsd/lib/librustc_fluent_macro-60e8ff74c2f2aaa5.so: No space available for static Thread Local Storage
  --> src/lib.rs:16:1
   |
16 | extern crate rustc_middle;
   | ^^^^^^^^^^^^^^^^^^^^^^^^^^

To fix this issue, the set of exclusions at