Description
Problem
Hi,
in my current project, I have a workspace that has an artifact dependency on one of its members. The workspace is built for the host arch, but the artifact dependency is always x86_64-unknown-none.
I would need to be able to specify -Zbuild-std=core,alloc for that x86_64 member, which is currently not possible. I can specify unstable.build-std in .cargo/config.toml, however that requires me specifying build.target as well, which doesn't work because then my workspace will also be built for that. If I don't specify the target, I get a panic no entry found for key.
thread 'main' panicked at src/tools/cargo/src/cargo/core/compiler/unit_dependencies.rs:178:34:
no entry found for key
stack backtrace:
0: 0x10165d700 - <std::sys::backtrace::BacktraceLock::print::DisplayBacktrace as core::fmt::Display>::fmt::h30f4b9ed62f3897b
1: 0x1016814a4 - core::fmt::write::h68122921d8b1a619
2: 0x101657db0 - std::io::Write::write_fmt::hac1f183862df87a2
3: 0x10165d5b4 - std::sys::backtrace::BacktraceLock::print::h1f1b6b5bdc96b0cd
4: 0x10165ea40 - std::panicking::default_hook::{{closure}}::heae1779b685357fb
5: 0x10165e890 - std::panicking::default_hook::h309e27147f9cc499
6: 0x10165f520 - std::panicking::rust_panic_with_hook::h6e33d145b73c56b6
7: 0x10165f14c - std::panicking::begin_panic_handler::{{closure}}::h1b530e3befd00369
8: 0x10165dbb0 - std::sys::backtrace::__rust_end_short_backtrace::h08b2dd416eec9a36
9: 0x10165edf4 - __rustc[30d06caa1ba95d]::rust_begin_unwind
10: 0x1016ed574 - core::panicking::panic_fmt::ha09de3336dfd93b2
11: 0x1016ed554 - core::option::expect_failed::hb3fc12b2cdb34fa4
12: 0x100e5eba0 - cargo[afe0554dd491e78]::core::compiler::unit_dependencies::build_unit_dependencies
13: 0x100e89284 - cargo[afe0554dd491e78]::ops::cargo_compile::create_bcx
14: 0x100e87cc0 - cargo[afe0554dd491e78]::ops::cargo_compile::compile_ws
15: 0x100cda224 - cargo[afe0554dd491e78]::ops::cargo_compile::compile_with_exec
16: 0x100cda164 - cargo[afe0554dd491e78]::ops::cargo_compile::compile
17: 0x10082bddc - cargo[bc5817d802847781]::commands::build::exec
18: 0x10084ca38 - <cargo[bc5817d802847781]::cli::Exec>::exec
19: 0x100844ae0 - cargo[bc5817d802847781]::main
20: 0x1007d7ec0 - std[54631d7a81de9e90]::sys::backtrace::__rust_begin_short_backtrace::<fn(), ()>
21: 0x1007e7668 - std[54631d7a81de9e90]::rt::lang_start::<()>::{closure#0}
22: 0x10164f7e4 - std::rt::lang_start_internal::h08b3d2187a7fcb0a
23: 0x10084f61c - _main
For this problem, I wouldn't mind if build-std would be active for all workspace crates, however it of course should build the right arch.
Proposed Solution
Either allow an additional key in the artifact dependency declaration (not so great IMO).
Or allow per-member .cargo/config.toml files, in which I can easily specify all that's required (awesome but huge effort probably).
Or don't require the build.target together with unstable.build-std, because the target should become clear from the crate that is being built (I think?).
Notes
My specific problem is that I want to implement stack unwinding for x86_64-unknown-none in my project, but it seems like the stack frames under panic! don't have unwind info - probably because I'm using the precompiled libcore. That's why I'd like to be able to compile it myself. Any alternative approaches besides adding this feature are more welcome.
Also, I'd like to keep using workspaces and bindeps, although I'm aware that those are an unstable feature.