IMHO Cook is following good development practices.
You need to know what you support.
If you are going to change, it must be planned somehow.
I find Torwalds reckless by changing his development environment before release.
If he really needs that computer to release the kernel, it must be stable one.
Even better: it should be a VM (hosted somewhere) or part of a CI-CD pipeline.
The real problem here was "-Werror", dogmatically fixing warnings, and using the position of privilege to push in last-minute commits without review.
Compilers will be updated, they will have new warnings, this has happened numerous times and will happen in the future. The linux kernel has always supported a wide range of compiler versions, from the very latest to 5+ years old.
I've ranted about "-Werror" in the past, but to try to keep it concise: it breaks builds that would and should otherwise work. It breaks older code with newer compiler and different-platform compiler. This is bad because then you can't, say, use the exact code specified/intended without modifications, or you can't test and compare different versions or different toolchains, etc. A good developer will absolutely not tolerate a deluge of warnings all the time, they will decide to fix the warnings to get a clean build, over a reasonable time with well-considered changes, rather than be forced to fix them immediately with brash disruptive code changes. And this is a perfect example why. New compiler fine, new warnings fine. Warnings are a useful feature, distinct from errors. "-Werror" is the real error.
With or without -Werror, you need your builds to be clean with the project's chosen compilers.
Linux decided, on a whim, that a pre-release of GCC 15 ought to suddenly be a compiler that the Linux project officially uses, and threw in some last-minute commits straight to main, which is insane. But even without -Werror, when the project decides to upgrade compiler versions, warnings must be silenced, either through disabling new warnings or through changing the source code. Warnings have value, and they only have value if they're not routinely ignored.
For the record, I agree that -Werror sucks. It's nice in CI, but it's terrible to have it enabled by default, as it means that your contributors will have their build broken just because they used a different compiler version than the ones which the project has decided to officially adopt. But I don't think it's the problem here. The problem here is Linus's sudden decision to upgrade to a pre-release version of GCC which has new warnings and commit "fixes" straight to main.
This is my take-away as well. Many projects let warnings fester until they hit a volume where critical warnings are missed amidst all the noise. That isn't ideal, but seems to be the norm in many spaces (for instance the nodejs world where it's just pages and pages of warnings and deprecations and critical vulnerabilities and...).
But pushing breaking changes just to suppress some new warning should not be the alternative. Working to minimize warnings in a pragmatic way seems more tenable.
Ironically, as a NodeJS dev, I was going to say the opposite: I'm very used to the idea that you have a strict set of warnings that block the build completely if they fail, and I find it very strange in the C world that this isn't the norm. But I think that's more to do with being able to pin dependencies more easily: by default, everyone on projects I work with uses the same set of dependencies always, including build departments and NodeJS versions. And any changes to that set of dependencies will be recorded as part of the repository history, so if be warnings/failures show up, it's very easy to see what caused it.
Whereas in a lot of the C (and C++, and even older Python) codebases I've seen, these sorts of dependencies aren't locked to the same extent, so it's harder to track upgrades, and therefore warnings are more likely to appear, well without warning.
But I think it's also probably the case that a C expert will produce codebases that have no warnings, and a C novice will produce codebases filled with warnings, and the same for JS. So I can imagine if you're just "visiting" the other language's ecosystem, you'll see worse projects and results than if you've spent a while there.
I find it surprising that linus bases his development and release tools based on whatever's in the repositories at that time. Surely it is best practice to pin to a specified, fixed version and upgrade as necessary, so everyone is working with the same tools?
This is common best practice in many environments...
Linus surely knows this, but here he's just being hard headed.
That can work, but it can also bring quite a few issues. Mozilla effectively does this; their build process downloads the build toolchain, including a specific clang version, during bootstrap, i.e., setting up the build environment.
This is super nice in theory, but it gets murky if you veer off the "I'm building current mainline Firefox path".
For example, I'm a maintainer of a Firefox fork that often lags a few versions behind. It has substantial changes, and we are only two guys doing the major work, so keeping up with current changes is not feasible. However, this is a research/security testing-focused project, so this is generally okay.
However, coming back to the build issue, apparently, it's costly to host all those buildchain archives. So they get frequently deleted from the remote repository, which leads to the build only working on machines that downloaded the toolchain earlier (i.e., not Github action runner, for example).
Given that there are many more downstream users of effectively a ton of kernel versions, this quickly gets fairly expensive and takes up a ton of effort unless you pin it to some old version and rarely change it.
So, as someone wanting to mess around with open source projects, their supporting more than 1 specific compiler version is actually quite nice.
Conceptually it's no different than any other build dependency. It is not expensive to host many versions. $1 is enough to store over 1000 compiler versions which would be overkill for the needs of the kernel.
Because then, if something that is expected to compile doesn't compile correctly, you know that you should check your compiler version. It is the exact same reason why you don't just specify which library your project depends on but also the libraries' version.
People are usually going to go through `make`, I don't see a reason that couldn't be instrumented to (by default) acquire an upstream GCC vs whatever forked garbage ends up in $PATH
Why would it go wrong, the ABI is stable and independent of compiler? You would hit issues with C++ but not C. I have certainly built kernels using different versions of GCC than what /lib stuff is compiled with, without issue.
You'd think that, but in effect kconfig/kbuild has many cases where they say "if the compiler supports flag X, use it" where X implies an ABI break. Per task stack protectors comes to mind.
I'm completely unsure whether to respond "it was stable, he was running a release version of Fedora" or "there's no such thing as stable under Linux".
The insanity is that the Kernel, Fedora and GCC are so badly coordinated that the beta of the compiler breaks the Kernel build (this is not a beta, this is a pre-alpha in a reasonable universe...is the Kernel a critical user of GCC? Apparently not), and a major distro packages that beta version of the compiler.
To borrow a phrase from Reddit: "everybody sucks here" (even Cook, who looks the best of everyone here, seems either oblivious or defeated about how clownshoes it is that released versions of major linux distros can't build the Kernel. The solution of "don't update to release versions" is crap).
(Writing this from a Linux machine, which I will continue using, but also sort of despise).
You need to know what you support. If you are going to change, it must be planned somehow.
I find Torwalds reckless by changing his development environment before release. If he really needs that computer to release the kernel, it must be stable one. Even better: it should be a VM (hosted somewhere) or part of a CI-CD pipeline.