check for std symbols

[gnzlbg]

Test whether the final rlib or binary contain any std symbols or not.

The llvm-tools-preview component contains an llvm-nm that can be used to list all symbols in a binary, and the cargo-binutils sub-command can be used to find the appropriate llvm-nm binary for the current toolchain (https://internals.rust-lang.org/t/llvm-tools-a-new-rustup-component-for-binary-inspection-objdump-nm-size-and-profiling-profdata/7830/9).

With that one can check whether the final binary contains any std library symbols, a check that must pass independently of what all other checks say.

[hobofan]

I explored that route, but ultimately got stuck on isolating the binary part out of the *.rlib files. Haven't had a look at llvm-tools-preview, though.

I'm generally pro doing that, though most likely as an optional thing if it requires llvm-tools-preview to be added as a component.

[hobofan]

@gnzlbg I tried out llvm-tools-preview and encountered the same problem as you did in rust-lang/rust#55729.

Apart from the The end of the file was unexpectedly encountered message the output does look pretty okay tough... I'm tempted to maybe build a hacky solution on top of that that ignores the exit code as long as the issue perists, and just grep the output for occurences of _<std.

Not the most beautiful solution, but probably the best we can do for post-compilation checks right now.

[gnzlbg]

Sounds good, that's what I ended up doing more or less. One might need to try using the nm of the llvm toolchain first, and if that does not exist, then try to use the systems nm. FWIW I get the same errors using both, so maybe just using the system's nm is ok at least for the beginning.

[hobofan]

Good news! At a recent meetup someone told me that I *.rlib files are just a tar-ed archive that contains object files (sound like I could've figured that out earlier🤦‍♂). I built a local proof of concept that then parses the object files with gimli and looks for a std namespace, and it seems to work quite well.

I'm currently working on adding that as a new mode to cargo-nono and hopefully will get a release with that out soon.