WebAssembly
Rewrite the build system with CMake
This commit is an attempt to provide a concrete path forward on WebAssembly/wasi-sdk#425. I personally think it's pretty important to get the ability to have more architectures here but at the same time I also think it's important to to take this as an opportunity to refactor and improve the build system of this repository. To that end this represents my attempt to improve the status quo.
This removes the old Makefile and replaces it with a CMake-based system to build all these projects. Overall this is intended to be a "no functional change" intended sort of refactoring. Changing build systems inevitably causes issues, however, so this change additionally has a very high likelihood of needing follow-up fixes. At a high enough level this commit introduces two major changes to how this repository is built:
- The
make-based system (the rootMakefile) is replaced with CMake. This additionally updates tests to use CMake. - A single "build" is split into either building a toolchain or building a sysroot. This enables builds to only build one or the other as necessary.
The first change, using CMake, is due to the fact that using make on Windows basically is not pleasant coupled with the fact that more advanced logic, such as changing flags, compilers, etc, is much easier with a CMake-based system. The second change is intended to cover the use case of #425 in addition to refactoring the current build.
Throughout this change I have intentionally not tried to keep a 1:1 correspondance with behaviors in the old Makefile because much of this PR is intended to address shortcomings in the old build system. A list of changes, improvements, etc, made here are:
-
CMake provides a much nicer portability story to Windows than
make. This is moving towards the direction of not needingbash, for example, to build an SDK. Currentlywasi-libcstill requires this, but that's now the only "hard" dependency. -
The set of targets built can now be configured for smaller builds and/or debugging just a single target. All WASI targets are still built by default but it's much easier to add/remove them.
-
Different targets are now able to be built in parallel as opposed to the unconditional serial-nature of the
Makefile. -
Use of
ninjais no longer required and separate build systems can be used if desired. -
The sysroot and the toolchain can now be built with different CMake build profiles. For example the
MakefilehardcodedMinSizeRelandRelWithDebInfoand this can now be much more easily customized by the SDK builder. -
Tarballs are now more consistently produced and named. For a tarball of the name
foo.tar.gzit's guaranteed that there's a single folderfoocreated when unpacking the tarball. -
The macOS binaries are no longer hybrid x64/arm64 binaries which greatly inflates the size of the SDK. There's now a separate build for each architecture.
-
CI now produces arm64-linux binaries. The sysroot is not built on the arm64-linux builder and the sysroot from the x86_64-linux builder is used instead.
-
Tests are almost ready to execute on Windows, there's just a few minor issues related to exit statuses and probably line endings which need to be worked out. Will require someone with a Windows checkout, however.
-
Tests are now integrated into CMake. This means that the wasm binaries are able to be built in parallel and the tests are additionally executed in parallel with
ctest. It is possible to build/run a single test. Tests no longer place all of their output in the source tree. -
Out-of-tree builds are now possible and the build/installation directories can both be customized.
-
CI configuration of Windows/macOS/Linux is much more uniform by having everything in one build matrix instead of separate matrices.
-
Linux builds are exclusively done in docker containers in CI now. CI no longer produces two Linux builds only for one to be discarded when artifacts are published.
-
Windows 32-bit builds are no longer produced in CI since it's expected that everyone actually wants the 64-bit ones instead.
-
Use of
ccacheis now automatically enabled if it's detected on the system. -
Many preexisting shell scripts are now translated to CMake one way or another.
-
There's no longer a separate build script for how to build wasi-sdk in docker and outside of docker which needs to be kept in sync, everything funnels through the same script.
-
The
docker/Dockerfilebuild of wasi-sdk now uses the actual toolchain built from CI and additionally doesn't duplicate various CMake-based configuration files.
Overall one thing I want to additionally point out is that I'm not CMake expert. I suspect there's lots of little stylistic and such improvements that can be made.
A few other points of note:
- To land this PR the set of required checks in this repository's settings are going to have to change (I don't have access to change that)
- I haven't updated the instructions for making a release yet. If there's agreement on this I'd like to land this and then I'll work through any changes there necessary.
- I've tried to leave comments in all the various places, but if anything is surprising and/or missing comments let me know and I'll add more.
I'm not the greatest fan of cmake I have to say. I tend to find shell scripts that are transliterated into cmake even harder to deal with than the originals.
To be clear I completely agree with you. I'm no fan of cmake myself, but AFAIK it's the only build-system-style solution that works across Windows/macOS/Linux. Shell scripts to me chiefly break down on Windows. I also think that cmake has a lot to offer once you get past the "wow that sure is cmake" since it has functions/if-else/loops/etc in addition to being able to define a build system which ends up being pretty flexibly. I definitely agree though that the syntax leaves a bit to be desired.
It would be very nice to make wasm-component-ld building logic optional, since downstream users may have other ways to provide the rust based tools and want to avoid cargo install during building of wasi-sdk.
I'm not necessarily in any rush to merge this, but I also want to pose a question as to what the next steps for this would be. For example do folks feel this should stay open for awhile to gather more feedback? Or is there anyone in particular I should reach out to and consult on this?
@TerrorJack happy to add other build options, should be pretty easy to do so. That being said I'd like to delve further into the motivations because I think it's best to have a consistent sysroot where possible (e.g. omitting wasm-component-ld would mean that the wasm32-wasip2 target wouldn't work), so mind opening an issue to discuss a bit further?
@alexcrichton Nope, just assuming wasm-component-ld is already built elsewhere and present in PATH. That shouldn't affect p2 sysroots.
Ok I'd still regardless like to discuss further (but probably not here since it's orthogonal). For example I'd like to understand why cargo install is inappropriate because if it's externally available then the versions could be out of sync and that can confuse what it means to have a particular version of wasi-sdk. (I'm trying to explain some questions here rather than simply say "let's discuss in an issue" but I'd prefer to follow-up in an issue)
Does this build system allow not to build clang/llvm before building the sdk?
Yes, it's possible to build just the sysroot since the build is split in two halves. One caveat is that due to how compiler-rt library lookup works the build system tries to install compiler-rt in the in-use toolchain's sysroot, so that will probably need tweaks over time.
I figured I'll solicit once more for thoughts on this, and pending that I'll try to work with @abrown later this week with respect to repo settings to merge.
@abrown has now removed the gates on specific status checks which enables this PR to merge. I'll wait for green CI and then merge it and then we'll re-enable the gates on the new status checks that this PR introduces.