Building on non-FreeBSD hosts
Until recently, FreeBSD could only be built on a FreeBSD host. However, most CI systems do not include FreeBSD build slaves by default. If we allow FreeBSD to be compiled on a non-FreeBSD host (current target is Linux and macOS) it would be much easier to use these CI systems. Furthermore, it would allow developers who do not have a FreeBSD system at work to use that to work on FreeBSD.
Why crossbuilding from non-FreeBSD didn't work
- Some build tools depend on host headers being compatible with target headers (e.g. localedef). This would require some refactoring of the xlocale headers to fix properly.
- The version of clang contained in the FreeBSD source tree cannot be bootstrapped with the makefiles from base since the config headers depend on FreeBSD
- Could build the bootstrap clang using CMake+ninja (which should also be much faster than the current Makefile solution), but that will be a lot of effort
- Current solution is to use upstream clang
- However, some features such as ifunc-noplt are not in upstream clang
- The build system often falls back to invoking binaries in $PATH
- This can cause strange build errors if that binary was not bootstrapped and an incompatible versions is executed
- can also happen when building on FreeBSD (e.g. running dtc from an old FreeBSD version)
Building with a clean $PATH D16815 fixes this problem since it requires all bootstrap tools to be listed explicitly
Current status
As of September 2020 all required patches have been merged to HEAD.
Instructions for building on Linux/macOS
Since Linux and macOS don't include a version of bmake by default, building should be done using the script tools/build/make.py which will bootstrap bmake before attempting to build. Additionally it will set the required XCC,XLD etc variables that are needed to build with an ExternalToolchain. If you have a recent version of bmake installed using homebrew or another package manager you can also set the required variables manually (the easiest way to obtain them is by running tools/build/make.py --debug)
Usage:
MAKEOBJDIRPREFIX=... ./tools/build/make.py buildworld TARGET=foo TARGET_ARCH=bar ...
Prerequisites on macOS
tools/build/make.py should work out-of-the box on macOS with clang and libarchive installed via homebrew:
brew install clang libarchive
Prerequisites on Linux
You will need a recent version of clang (ideally 10.0) and the libarchive + libbz2 headers.
Open issues
Name |
STATUS |
Owner |
Review |
Commits |
Comments |
MK_PMC broken |
Committed |
jevents doesn't emit output on macOS |
|||
MK_BSNMP broken |
Committed |
|
The makefiles for libsnmp use ls -D which is not supported on macOS+Linux |
||
MK_CDDL broken |
Committed |
Some of the CDDL bootstrap tools don't compile yet |
|||
MK_BOOT broken |
Committed |
|
? |
? |
BOOT contains some assembly files that cannot be built with clang |
MK_TESTS broken |
Committed |
at least one of the test makefiles uses dd status=none which is not supported on Linux/macOS |
|||
MK_LOCALES broken |
Committed |
localedef requires the host xlocale headers to be compatible with the target. Would need to namespace those headers to avoid conflicting with the host |
|||
Clang+LLD cannot be built |
Not started/Bad idea for bootstrap |
|
This requires tablegen to be bootstrapped but that won't work with the existing makefiles/config.h. Using an external toolchain is preferable for bootstrapping. Unfortunately this means the target system will not have a compiler, but it can always be installed using pkg. |
||
Building without inheriting $PATH |
Committed |
This avoids invoking binaries that are incompatible |
|||
Add compatibility headers for bootstrap phase |
Committed |
Allows bootstrapping tools without making changing the source code to be portable |
|||
Add wrapper script to bootstrap bmake |
Committed |
Needed since macOS/Linux don't include bmake by default |