buildRustCrate: Add "-r" to cp to make it work under Mac OS

[kolloch]

Motivation for this change

This fixes errors such as these on Mac OS:

Building src/lib.rs (hello_world_lib_and_bin)
Running rustc --crate-name hello_world_lib_and_bin src/lib.rs --out-dir target/lib --emit=dep-info,link -L dependency=target/deps --cap-lints allow -C debuginfo=2 -C codegen-units=1 --remap-path-prefix=/private/var/folders/vj/wn31skn95g9fz4l9wdm5l5kh0000gn/T/nix-build-rust_hello_world_lib_and_bin-0.1.0.drv-0=/ --cfg feature="default" --edition 2018 -C metadata=06b67cb1f9 -C extra-filename=-06b67cb1f9 --crate-type lib --color always
unpacking sources
unpacking source archive /nix/store/bfrhy6p2dzb8qnixqzhgp2sa3770a69z-ansi_term-0.11.0.tar.gz
unpacking sources
unpacking source archive /nix/store/s8x3gwl0y2a5j4ihxpnnzzpl1v0c9vvi-bitflags-1.2.1.tar.gz
Running rustc --crate-name cfg_test src/main.rs --crate-type bin -C debuginfo=2 -C codegen-units=1 --remap-path-prefix=/private/var/folders/vj/wn31skn95g9fz4l9wdm5l5kh0000gn/T/nix-build-rust_cfg-test-0.1.0.drv-0=/ --cfg feature="default" --edition 2018 --out-dir target/bin --emit=dep-info,link -L dependency=target/deps --extern cfg_test=target/lib/libcfg_test-5198681f4a.rlib --cap-lints allow --color always
cp: -r not specified; omitting directory 'target/bin/hello_world_bin.dSYM'

Things done

• Tested using sandboxing (nix.useSandbox on NixOS, or option sandbox in nix.conf on non-NixOS linux)
• Ran crate2nix tests on
  • NixOS
  • macOS
  • other Linux distributions
• Tested via one or more NixOS test(s) if existing and applicable for the change (look inside nixos/tests)
• Tested compilation of all pkgs that depend on this change using nix-shell -p nixpkgs-review --run "nixpkgs-review wip"
• Tested execution of all binary files (usually in ./result/bin/)
• Determined the impact on package closure size (by running nix path-info -S before and after)
• Ensured that relevant documentation is up to date
• Fits CONTRIBUTING.md.

[andir]

I am not sure this is right. This might fix the issue but it looks like it adds "trash" to $out/bin?

We clearly do not want to have files (or directories) named 'target/bin/hello_world_bin.dSYM' in $out/bin? Am I missing something.

[kolloch]

I don't know. I experimented a bit with omitting .out Directories, it turned out that it was needed. I am not really interested in spending much time on Mac OS but the current version is broken.

[kolloch]

DSYM files might make sense. They contain debugging symbols and might be useful for better stack traces.

[LnL7]

It's not really clear to me what the actual "error" is here.

Packages in nixpkgs (should) run release builds and are striped by default. If you want this for debugging purposes, handling this with a debug output, similar to what seprateDebugInfo = true; does on linux for dwarf symbols would be the way to go.

[andir]

Mhm, I can't really test anything regarding MacOS since I do not own a single apple device. I guess we either use this or we keep it in a broken state :/ Is there someone that could provide SSH access into a box for nixpkgs development on Macs? Not looking for a paid service.

[LnL7]

Disabling whatever causes the separate debug symbols to be created would be the best fix for now I think (I notice -C debuginfo=2 in the output).

That said having proper support for debug info on darwin would be great, but that's probably a bit out of scope for this.

[LnL7]

Seems like just moving it works so adding a setup-hook similar to separateDebugInfo should be pretty straightforward.

https://gist.github.com/LnL7/506e719a5fa339520877acecd4fe3a9f

[andir]

I think we should start adding some "docstring"-like comments to these function (as we do in crate2nix). During the discussion of #83379 I was told that currently it isn't really obvious how they work. I intend to refactor the test runner once all the current PRs have been merged and things have settled down.

[kolloch]

I am all for docs! I added some (push still outstanding).

[kolloch]

Seems like just moving it works so adding a setup-hook similar to separateDebugInfo should be pretty straightforward.

https://gist.github.com/LnL7/506e719a5fa339520877acecd4fe3a9f

I tried to do that but it didn't work for me. E.g. on Mac OS compgen -G or ${debug:-out}. Does it use a different shell? Annoying. The error might be mine but this is a timeout for me.

I found out that the dSYM files are only generated if release = false is specified to buildRustCrate. I think that is totally acceptable. Furthermore, we added additional files to the output before (e.g. dependency files which I removed now) which nobody noticed before.

[kolloch]

And I am getting an unrelated error on Mac OS (I was quite confused because I first thought that it was introduced by my changes):

https://gist.github.com/kolloch/311487d7b960f4a79f57c13926635cb7

[kolloch]

When I revert the two linkorder PRs, it works:

peter@dipkus: ~/nixpkgs$ git revert d8b853799d6658582a6039be8febfbd925d967aa
[master 653a421b60e] Revert "buildRustCrate: don't sort link flags"
 2 files changed, 6 insertions(+), 1 deletion(-)

peter@dipkus: ~/nixpkgs$ git revert 2f7fb1c49732105c8937b66b7d92402c04546073
[master 49cc1eda0ea] Revert "buildRustCrateTests: add regression test for link order"
 1 file changed, 1 insertion(+), 53 deletions(-)

peter@dipkus: ~/nixpkgs$ nix-build -k -A buildRustCrateTests
/nix/store/jg9p6p7zz66pfj4vf3cv71sbxjiiq34v-buildRustCrate-tests

(Which is kind of a noop because I also delete the relevant test)

[andir]

Sorry for that. I fixed those and opened a PR for review: #83616

[kolloch]

No worries, @andir! "Wo gehobelt wird, da Fallen Spaene."

Back to this PR. Given

1. that the problem only appears with release = false
2. and I made thinks better by actually adding tests that ensure that no random junk files pop up for binaries and rlibs,

I think that the PR is in reasonable shape now. If you have any actionable feedback, let me now.

[andir]

Tested on Linux & MacOS.

MacOS did pass after I rebased this onto master. 👍

Thank you for fixing this.