RUSTFLAGS=--cap-lints=allow causes output of --print=file-names missing when learning about target-specific information from rustc

[zjp-CN]

I tried this code:

#![no_std]
pub fn add(left: u64, right: u64) -> u64 {
    left + right
}

Run it with RUSTFLAGS=--cap-lints=allow cargo check --target aarch64-unknown-none-softfloat

I expected to see this happen: it compiles.

Instead, this happened: it emits error

error: output of --print=file-names missing when learning about target-specific information from rustc
command was: `/root/.cargo/bin/sccache /root/.rustup/toolchains/nightly-x86_64-unknown-linux-gnu/bin/rustc - --crate-name ___ --print=file-names --cap-lints=allow --target
 aarch64-unknown-none-softfloat --crate-type bin --crate-type rlib --crate-type dylib --crate-type cdylib --crate-type staticlib --crate-type proc-macro --print=sysroot --
print=split-debuginfo --print=crate-name --print=cfg`

--- stdout
___
lib___.rlib
lib___.a
/root/.rustup/toolchains/nightly-x86_64-unknown-linux-gnu
off
___
debug_assertions
fmt_debug="full"
overflow_checks
panic="abort"
proc_macro
relocation_model="static"
target_abi="softfloat"
target_arch="aarch64"
target_endian="little"
target_env=""
target_has_atomic
target_has_atomic="128"
target_has_atomic="16"
target_has_atomic="32"
target_has_atomic="64"
target_has_atomic="8"
target_has_atomic="ptr"
target_has_atomic_equal_alignment="128"
target_has_atomic_equal_alignment="16"
target_has_atomic_equal_alignment="32"
target_has_atomic_equal_alignment="64"
target_has_atomic_equal_alignment="8"
target_has_atomic_equal_alignment="ptr"
target_has_atomic_load_store
target_has_atomic_load_store="128"
target_has_atomic_load_store="16"
target_has_atomic_load_store="32"
target_has_atomic_load_store="64"
target_has_atomic_load_store="8"
target_has_atomic_load_store="ptr"
target_os="none"
target_pointer_width="64"
target_vendor="unknown"
ub_checks

• Background (cargo-semver-checks): error: output of --print=file-names missing when learning about target-specific information from rustc when --target is specified obi1kenobi/cargo-semver-checks#1068
• Might be due to cargo relies on unknown crate type warnings to detect if a target supports crate types, which can be suppressed by -Awarnings and thus break cargo's detection #116626 (comment)

Meta

rustc --version --verbose:

rustc 1.85.0-nightly (7f75bfa1a 2024-12-30)
binary: rustc
commit-hash: 7f75bfa1ad4e9a9d33a179a90603001515e91991
commit-date: 2024-12-30
host: x86_64-unknown-linux-gnu
release: 1.85.0-nightly
LLVM version: 19.1.6

[Noratrieb]

Yeah, this is #116626, the warning gets dropped due to cap lints. A workaround is to use cap lints warn, which will still print the warning and still avoid errors the build due to warnings.