[RFC] build: namespace generated headers with `zephyr/`

[ycsin]

Introduction

Two years ago there was a header migration in #45410 to namespace all the headers in the include directory to include/zephyr, however the build-time generated headers are (still) not namespaced, i.e.:

• app_version.h
• cmake_intdef.h
• core-isa-dM.h
• devicetree_generated.h
• driver-validation.h
• kobj-types-enum.h
• linker-kobject-prebuilt-data.h
• mcuboot_version.h
• offsets.h
• otype-to-size.h
• otype-to-str.h
• strerror_table.h
• strsignal_table.h
• syscall_list.h
• version.h
• zsr.h
• Kconfig headers (autoconf.h)
• and all the syscalls headers

Generated headers, especially version.h, can easily conflict with other libraries & user applications. This RFC is proposing to namespace the generated headers into the zephyr/ directory as well.

Problem description

Some of the generated headers have pretty generic names, i.e.: version.h, and can potentially conflict with other library / user applications. Ideally, all Zephyr's headers, in-tree or generated, should be namespaced with zephyr/.

Proposed change

The generated headers previously in build/zephyr/include/generated/ will now be placed in build/zephyr/include/generated/zephyr/, Zephyr sources that are including these headers will be updated accordingly, i.e.:

zephyr/kernel/banner.c

Line 10 in 114548e

#include <version.h>

will be changed to

#include <zephyr/version.h>

Detailed RFC

The task involves modifying CMake files and scripts to output generated headers in the include/generated/zephyr/ directory, updating dependencies on these headers accordingly, changing include paths for in-tree sources, creating a compatibility Kconfig for uninterrupted user application builds, and updating migration and release notes with details on this change and its mitigation steps.

Proposed change (Detailed)

• Modify CMake files and scripts to output headers to the include/generated/zephyr/ directory
• Update CMake files and scripts to depend on headers in the include/generated/zephyr/ directory
• Update in-tree sources' include paths to zephyr/<header.h>
• Create a compatibility Kconfig so that user applications will still continue to build
• Update the migration/release notes about the change, and steps to mitigate

Dependencies

External libraries and user applications can be affected, in that case they may use the migration script.

• sof
  • zephyr: namespace the generated version.h - take 1 thesofproject/sof#8459
  • zephyr: namespace the generated version.h sof#34
• percepio
  • zephyr: namespace the generated version.h percepio/percepio#5
  • zephyr: namespace the generated version.h percepio/percepio#6
  • zephyr: namespace the generated version.h percepio#10

Concerns and Unresolved Questions

Can't think of any

Alternatives

Rely on all external libaries & user applications to namespace their header so that no conflicts can occur.

[henrikbrixandersen]

Thanks! I'd very much like to see this happen.