Hello,

A number of files in the Mbed TLS source tree are automatically generated from other files, with a content that does not depend on the platform or configuration. We are considering removing the generated files from the development branch in Git, at least during the work towards Mbed TLS 3.0. This would affect at least the development branch until the 3.0 release, and may affect the development_2.x branch and the development branch after the 3.0 release. Long-time support branches and official releases will continue to have these source files in the Git tree.

The reason to remove the generated files is to facilitate development, especially with the restructuring that is happening as we prepare a new major version of the library. This is an experimental change; depending on how effective it is, we may or may not wish to restore the generated files on the development branch when 3.0 stabilizes. It's also still possible that we will not go ahead with this change, depending on the impact on our CI and on the feedback we receive.

The affected files are: * Two library source files: library/error.c and library/version_features.c. * Parts of some test programs: programs/test/query_config.c and programs/psa/psa_constant_names_generated.c. * The Visual Studio project files. * Some unit test data files.

What does this change for you?

**If you were using a long-time support branch or an official release**: no change.

**If you were using the supplied GNU Makefile**: there should be no effective change.

**If you were using CMake, Visual Studio or custom build scripts** on the development branch: Perl (>=5.8) will be required to generate some library sources and to generate the Visual Studio project files. Python (>=3.4) was already required to run config.py and to build the unit tests. Note that the generated files are independent of the Mbed TLS configuration, so if your deployment has a pre-configuration step, you can generate the files at this step: no new tool is required after the library is configured.

The ongoing work (not complete yet as I write) is at https://github.com/ARMmbed/mbedtls/pull/4395 if you want to see what this change means concretely.

We are aware that the additional dependencies are a burden in some environments, which is why we will definitely not change anything to releases or to current and future long-time support branches. If you are building Mbed TLS from the development branch and this change affects you, please let us know what constraints apply to your environment.

Best regards,