safer_ffi may randomly generate empty headers

[pan93412]

Abstract

Sometimes safer_ffi generates an empty headers like the following screenshot on my Mac:

After setting up the breakpoint and debugging, I found that inventory::iter ended up really fast – like nothing registered:

As it works on my another Ubuntu machine, I guess it is related to dtolnay/inventory#9? I tried to upgrade Inventory to 3.0.1; however, the compilation failed:

Not really sure how to fix it.

Expected Behavior (on my Ubuntu machine)

Metadata

• rustc version: rustc 1.65.0-nightly (20ffea693 2022-08-11)
• cargo version cargo 1.65.0-nightly (ce40690a5 2022-08-09)
• OS version macOS Monterey 12.5 (ARM64)
• Reproducible Repo: https://github.com/pan93412/libstock-ffi/tree/e87b04cf6e1bd9394db656315f1dbd2975418c95

[danielhenrymantilla]

Thanks for the very detailed, link-backed, and extended report 🙏

[danielhenrymantilla]

[Continuing from #132]

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Maybe we should report it to the upstream? Not sure about it.

Yeah, maybe; although if we do that we'd need to really reduce the example, right now there is too much safer-ffi glue to report it to inventory.

Until then, you could try to work around the limitation, in and of itself, by making more modules pub, I guess:

• e.g., using https://docs.rs/visibility

  you could try to slap #[cfg_attr(feature = "headers", visibility::make(pub))] on your modules and see how it goes 🤷

[pan93412]

It seems not working. However, the symbols exported from bin gen-headers are less than those from the static library file – including “last_error_length” and something else:

• lib: symbols.libwmjtyd-libstock.txt
• bin: symbols.gen-header.txt

Although my Ubuntu machine also did not export them, maybe we can find some clues inside these symbol tables?

• lib: symbols.lib.ubuntu.txt
• bin: symbols.gen-header.ubuntu.txt

(Note that I exported them with nc (binfile) > somewhere.txt)

[danielhenrymantilla]

dtolnay/linkme#31 (comment) seems to suggest the inventory bug is still around 😬

[pan93412]

@danielhenrymantilla I resolved it with a weird way – I switched my linker to mold (for macOS), and it seems work now…? 😂

I'll continue observing this issue, but at least it works at this moment 😄

[danielhenrymantilla]

Great news! Having a workaround for this ought to be quite useful, even if it's not an actual solution (e.g., somebody may need to use something different than mold for other reasons on their project 😅).

Let's close this issue since safer-ffi (nor inventory) can't really fix it, it's up to Cargo/rustc to do it.
But further discussion here is still welcome.