Tips on handling `ffi-check`?

[clin1234]

In my fork, when running CI tests, against Python 3.14, errors spew in the form of these:

error[E0609]: no field `ob_base` on type `_PyGenObject`
  --> src/main.rs:45:13
   |
45 |             pyo3_ffi_check_macro::for_all_fields!($name, check_field);
   |             ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
...
70 |     pyo3_ffi_check_macro::for_all_structs!(check_struct);
   |     ---------------------------------------------------- in this macro invocation
   |
   = note: this error originates in the macro `pyo3_ffi_check_macro::for_all_fields` which comes from the expansion of the macro `pyo3_ffi_check_macro::for_all_structs` (in Nightly builds, run with -Z macro-backtrace for more info)

error[E0609]: no field `gi_weakreflist` on type `_PyGenObject`
  --> src/main.rs:45:13
   |
45 |             pyo3_ffi_check_macro::for_all_fields!($name, check_field);
   |             ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
...
70 |     pyo3_ffi_check_macro::for_all_structs!(check_struct);
   |     ---------------------------------------------------- in this macro invocation
   |
   = note: this error originates in the macro `pyo3_ffi_check_macro::for_all_fields` which comes from the expansion of the macro `pyo3_ffi_check_macro::for_all_structs` (in Nightly builds, run with -Z macro-backtrace for more info)

error[E0609]: no field `gi_name` on type `_PyGenObject`
  --> src/main.rs:45:13
   |
45 |             pyo3_ffi_check_macro::for_all_fields!($name, check_field);
   |             ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
...
70 |     pyo3_ffi_check_macro::for_all_structs!(check_struct);
   |     ---------------------------------------------------- in this macro invocation
   |
   = note: this error originates in the macro `pyo3_ffi_check_macro::for_all_fields` which comes from the expansion of the macro `pyo3_ffi_check_macro::for_all_structs` (in Nightly builds, run with -Z macro-backtrace for more info)

error[E0609]: no field `gi_qualname` on type `_PyGenObject`
  --> src/main.rs:45:13
   |
45 |             pyo3_ffi_check_macro::for_all_fields!($name, check_field);
   |             ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
...
70 |     pyo3_ffi_check_macro::for_all_structs!(check_struct);
   |     ---------------------------------------------------- in this macro invocation
   |
   = note: this error originates in the macro `pyo3_ffi_check_macro::for_all_fields` which comes from the expansion of the macro `pyo3_ffi_check_macro::for_all_structs` (in Nightly builds, run with -Z macro-backtrace for more info)

error[E0609]: no field `gi_exc_state` on type `_PyGenObject`
  --> src/main.rs:45:13
   |
45 |             pyo3_ffi_check_macro::for_all_fields!($name, check_field);
   |             ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
...
70 |     pyo3_ffi_check_macro::for_all_structs!(check_struct);
   |     ---------------------------------------------------- in this macro invocation
   |
   = note: this error originates in the macro `pyo3_ffi_check_macro::for_all_fields` which comes from the expansion of the macro `pyo3_ffi_check_macro::for_all_structs` (in Nightly builds, run with -Z macro-backtrace for more info)

error[E0609]: no field `gi_origin_or_finalizer` on type `_PyGenObject`
  --> src/main.rs:45:13
   |
45 |             pyo3_ffi_check_macro::for_all_fields!($name, check_field);
   |             ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
...
70 |     pyo3_ffi_check_macro::for_all_structs!(check_struct);
   |     ---------------------------------------------------- in this macro invocation
   |
   = note: this error originates in the macro `pyo3_ffi_check_macro::for_all_fields` which comes from the expansion of the macro `pyo3_ffi_check_macro::for_all_structs` (in Nightly builds, run with -Z macro-backtrace for more info)

error[E0609]: no field `gi_hooks_inited` on type `_PyGenObject`
  --> src/main.rs:45:13
   |
45 |             pyo3_ffi_check_macro::for_all_fields!($name, check_field);
   |             ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
...
70 |     pyo3_ffi_check_macro::for_all_structs!(check_struct);
   |     ---------------------------------------------------- in this macro invocation
   |
   = note: this error originates in the macro `pyo3_ffi_check_macro::for_all_fields` which comes from the expansion of the macro `pyo3_ffi_check_macro::for_all_structs` (in Nightly builds, run with -Z macro-backtrace for more info)

error[E0609]: no field `gi_closed` on type `_PyGenObject`
  --> src/main.rs:45:13
   |
45 |             pyo3_ffi_check_macro::for_all_fields!($name, check_field);
   |             ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
...
70 |     pyo3_ffi_check_macro::for_all_structs!(check_struct);
   |     ---------------------------------------------------- in this macro invocation
   |
   = note: this error originates in the macro `pyo3_ffi_check_macro::for_all_fields` which comes from the expansion of the macro `pyo3_ffi_check_macro::for_all_structs` (in Nightly builds, run with -Z macro-backtrace for more info)

error[E0609]: no field `gi_running_async` on type `_PyGenObject`
  --> src/main.rs:45:13
   |
45 |             pyo3_ffi_check_macro::for_all_fields!($name, check_field);
   |             ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
...
70 |     pyo3_ffi_check_macro::for_all_structs!(check_struct);
   |     ---------------------------------------------------- in this macro invocation
   |
   = note: this error originates in the macro `pyo3_ffi_check_macro::for_all_fields` which comes from the expansion of the macro `pyo3_ffi_check_macro::for_all_structs` (in Nightly builds, run with -Z macro-backtrace for more info)

error[E0609]: no field `gi_frame_state` on type `_PyGenObject`
  --> src/main.rs:45:13
   |
45 |             pyo3_ffi_check_macro::for_all_fields!($name, check_field);
   |             ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
...
70 |     pyo3_ffi_check_macro::for_all_structs!(check_struct);
   |     ---------------------------------------------------- in this macro invocation
   |
   = note: this error originates in the macro `pyo3_ffi_check_macro::for_all_fields` which comes from the expansion of the macro `pyo3_ffi_check_macro::for_all_structs` (in Nightly builds, run with -Z macro-backtrace for more info)

error[E0609]: no field `gi_iframe` on type `_PyGenObject`
  --> src/main.rs:45:13
   |
45 |             pyo3_ffi_check_macro::for_all_fields!($name, check_field);
   |             ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
...
70 |     pyo3_ffi_check_macro::for_all_structs!(check_struct);
   |     ---------------------------------------------------- in this macro invocation
   |
   = note: this error originates in the macro `pyo3_ffi_check_macro::for_all_fields` which comes from the expansion of the macro `pyo3_ffi_check_macro::for_all_structs` (in Nightly builds, run with -Z macro-backtrace for more info)

error[E0609]: no field `_padding` on type `_object`
  --> src/main.rs:45:13
   |
45 |             pyo3_ffi_check_macro::for_all_fields!($name, check_field);
   |             ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
...
70 |     pyo3_ffi_check_macro::for_all_structs!(check_struct);
   |     ---------------------------------------------------- in this macro invocation
   |
   = note: this error originates in the macro `pyo3_ffi_check_macro::for_all_fields` which comes from the expansion of the macro `pyo3_ffi_check_macro::for_all_structs` (in Nightly builds, run with -Z macro-backtrace for more info)

Reproducible by running cargo run --manifest-path=pyo3-ffi-check/Cargo.toml

Any tips derived from adding prior CPython releases would be appreciated.

[clin1234]

For context, compare the definition of PyGenObject in 3.14 vs in 3.13

[ngoldbaum]

The way to fix this is to add support for 3.14 in pyo3-ffi and update the FFI definitions.

We generally don't add support for new Python versions until the first beta, since the API and ABI aren't stable until then.

That said, because of #4904 I think there's a case to be made to do that a little early this year so we can add TSAN testing on the free-threaded build using 3.14, which has a number of thread safety fixes that haven't been backported to 3.13.