by BwackNinja | 2025-04-02 05:05:22+00:00
> The same applies to PAM word for word.

That's one of the reasons that OpenBSD is rather compelling. BSDAuth doesn't open arbitrary libraries to execute code, it forks and execs binaries so it doesn't pollute your program's namespace in unpredictable ways.

> It's true that there's something of a problem where two copies of a libc can't coexist in a process...

That's the meat of this article. It goes beyond complaining about a relatable issue and talks about the work and research they've done to see how it can be mitigated. I think it's a neat exercise to wonder how you could restructure a libc to allow multi-libc compatibility, but question why anyone would even want to statically link to libc in a program that dlopen's other libraries. If you're worried about a stable ABI with your libc, but acknowledge that other libraries you use link to a potentially different and incompatible libc thus making the problem even more complicated, you should probably go the BSDAuth route instead of introducing both additional complexity and incompatibility with existing systems. I think almost everything should be suitable for static linking and that Drepper's clarification is much more interesting than the rant. Polluting the global lib directory with a bunch of your private dependencies should be frowned upon and hides the real scale of applications. Installing an application shouldn't make the rest of your system harder to understand, especially when it doesn't do any special integration. When you have to dynamically link anyway:

> As for why you’d actually want to dlopen from a static executable, there’s one killer app: exokernels, loading (parts of) system-provided drivers into your process for speed.

If you're dealing with system resources like GPU drivers, those should be opaque implementations loaded by intermediaries like libglvnd. [1] This comes to mind as even more reason why dynamic dependencies of even static binaries are terrible. The resolution works, but it would be better if no zlib symbols would leak from mesa at all (using --exclude-libs and linking statically) so a compiled dependency cannot break the program that depends on it. So yes, I agree that dynamic dependencies of static libraries should be static themselves (though enforcing that is questionable), but I don't agree that the libc should be considered part of that problem and statically linked as well. That leads us to:

> ... when done right they don't even require both sides to share a malloc implementation

Better API design for libraries can eliminate a lot of these issues, but enforcing that is much harder problem in the current landscape where both sides are casually expected to share a malloc implementation -- hence the complication described in the article. "How can we force everything that exists into a better paradigm" is a lot less practical of a question than "what are the fewest changes we'd need to ensure this would work with just a recompile". I agree with the idea of a "narrow waist of an interface", but it's not useful in practice until people agree where the boundary should be and you can force everyone to abide by it.

[1] https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/28...