Re: rust library returns "Invalid target name: 'x86_64-pc-cygwin'"

Enabling both envars produces fuller backtrace, as below.

On Sun, 22 Feb 2026, Dr Bean via Cygwin wrote:

> I'm trying to build tooi, a python mastodon TUI 
> (https://codeberg.org/ihabunek/tooi), which depends on 
> pydantic, a python-rust data validation module.

> Building with python-3.12, in a venv virtual 
> environment, invoking `pip3 install .`,
> pydantic fails with the message,

>   Building wheel for pydantic-core (pyproject.toml) ... error
>   error: subprocess-exited-with-error

>   × Building wheel for pydantic-core (pyproject.toml) did not run successfully.
>   │ exit code: 1
>   ╰─> [22 lines of output]
>       Running `maturin pep517 build-wheel -i /home/drbean/dot/browser/tooi/.venv.312/bin/python3 --compatibility off`
>       🍹 Building a mixed python/rust project
>       🔗 Found pyo3 bindings
>       🐍 Found CPython 3.12 at /home/drbean/dot/browser/tooi/.venv.312/bin/python3
>       📡 Using build options bindings from pyproject.toml
>          Compiling proc-macro2 v1.0.86
>          Compiling unicode-ident v1.0.12
>          Compiling target-lexicon v0.13.2
>       error: failed to run custom build command for `target-lexicon v0.13.2`

>       Caused by:
>         process didn't exit successfully: `/tmp/pip-install-jvwnp9e1/pydantic-core_f4b932677649467ab031f90bc26a5065/target/release/build/target-lexicon-a0d8869a1d22c23b/build-script-build` (exit status: 101)
>         --- stderr

>         thread 'main' (1) panicked at /home/drbean/.cargo/registry/src/index.crates.io-1949cf8c6b5b557f/target-lexicon-0.13.2/build.rs:52:54:
>         Invalid target name: 'x86_64-pc-cygwin'
>         note: run with `RUST_BACKTRACE=1` environment variable to display a backtrace
>       warning: build failed, waiting for other jobs to finish...
>       💥 maturin failed
>         Caused by: Failed to build a native library through cargo
>         Caused by: Cargo build finished with "exit status: 101": `env -u CARGO PYO3_BUILD_EXTENSION_MODULE="1" PYO3_ENVIRONMENT_SIGNATURE="cpython-3.12-64bit" PYO3_PYTHON="/home/drbean/dot/browser/tooi/.venv.312/bin/python3" PYTHON_SYS_EXECUTABLE="/home/drbean/dot/browser/tooi/.venv.312/bin/python3" "cargo" "rustc" "--profile" "release" "--message-format" "json-render-diagnostics" "--manifest-path" "/tmp/pip-install-jvwnp9e1/pydantic-core_f4b932677649467ab031f90bc26a5065/Cargo.toml" "--lib" "--crate-type" "cdylib"`
>       Error: command ['maturin', 'pep517', 'build-wheel', '-i', '/home/drbean/dot/browser/tooi/.venv.312/bin/python3', '--compatibility', 'off'] returned non-zero exit status 1
>       [end of output]

>   note: This error originates from a subprocess, and is likely not a problem with pip.
>   ERROR: Failed building wheel for pydantic-core
> Successfully built toot-tooi
> Failed to build pydantic-core

> Running with RUST_BACKTRACE=1 and then RUST_BACKTRACE=full, produces
> the same output but in addition the backtrace,

> --->%

>       error: failed to run custom build command for `target-lexicon v0.13.2`
>       note: To improve backtraces for build dependencies, set the CARGO_PROFILE_RELEASE_BUILD_OVERRIDE_DEBUG=true environment variable to enable debug information generation.

>       Caused by:
>         process didn't exit successfully: `/tmp/pip-install-i6xwee_g/pydantic-core_d54b807af2e64234b3895bffc7166967/target/release/build/target-lexicon-a0d8869a1d22c23b/build-script-build` (exit status: 101)
>         --- stderr

>         thread 'main' (1) panicked at /home/drbean/.cargo/registry/src/index.crates.io-1949cf8c6b5b557f/target-lexicon-0.13.2/build.rs:52:54:
>         Invalid target name: 'x86_64-pc-cygwin'
>         stack backtrace:
>            0:        0x10045e9b0 - <unknown>
>            1:        0x10048d1aa - <unknown>
>            2:        0x1004186ff - <unknown>
>            3:        0x10042a0e5 - <unknown>
>            4:        0x100431ba2 - <unknown>
>            5:        0x100431a1a - <unknown>
>            6:        0x100432367 - <unknown>
>            7:        0x100432132 - <unknown>
>            8:        0x10042a21f - <unknown>
>            9:        0x10040fece - <unknown>
>           10:        0x10049db01 - <unknown>
>           11:        0x1004091bd - <unknown>
>           12:        0x10040ae1c - <unknown>
>           13:        0x100408f9d - <unknown>
>           14:        0x1004099b6 - <unknown>
>           15:        0x1004094b9 - <unknown>
>           16:        0x100401bac - <unknown>
>           17:        0x10041c045 - <unknown>
>           18:        0x100401b97 - <unknown>
>           19:        0x10040d80f - <unknown>
>           20:     0x7ffc3dbf80f3 - <unknown>
>           21:     0x7ffc3dbf5cd5 - <unknown>
>           22:     0x7ffc3dbf5d8b - <unknown>
>           23:                0x0 - <unknown>
>       warning: build failed, waiting for other jobs to finish...

> ------>%

> Running with the advised
> CARGO_PROFILE_RELEASE_BUILD_OVERRIDE_DEBUG=true envar
> produces the same output as with no envars.

> Reading from a "Platform" dropdown on a target-lexicon 
> doc page, https://docs.rs/crate/target-lexicon/latest
> the supported platforms appear to be

> aarch64-apple-darwin
> aarch64-unknown-linux-gnu
> i686-pc-windows-msvc
> x86_64-pc-windows-msvc
> x86_64-unknown-linux-gnu

> That is, no x86_64-pc-cygwin

Enabling both RUST_BACKTRACE=full and 
CARGO_PROFILE_RELEASE_BUILD_OVERRIDE_DEBUG=true
produces more information:

  × Building wheel for pydantic-core (pyproject.toml) did not run successfully.
  │ exit code: 1
  ╰─> [91 lines of output]
      Running `maturin pep517 build-wheel -i /home/drbean/dot/browser/tooi/.venv.312/bin/python3 --compatibility off`
      🍹 Building a mixed python/rust project
      🔗 Found pyo3 bindings
      🐍 Found CPython 3.12 at /home/drbean/dot/browser/tooi/.venv.312/bin/python3
      📡 Using build options bindings from pyproject.toml
         Compiling proc-macro2 v1.0.86
         Compiling unicode-ident v1.0.12
         Compiling target-lexicon v0.13.2
      error: failed to run custom build command for `target-lexicon v0.13.2`

      Caused by:
        process didn't exit successfully: `/tmp/pip-install-s56o7awx/pydantic-core_db6fcc382f8942f1b53e915621dc0eb1/target/release/build/target-lexicon-64e748e5367b5657/build-script-build` (exit status: 101)
        --- stderr

        thread 'main' (1) panicked at /home/drbean/.cargo/registry/src/index.crates.io-1949cf8c6b5b557f/target-lexicon-0.13.2/build.rs:52:54:
        Invalid target name: 'x86_64-pc-cygwin'
        stack backtrace:
           0:        0x100460b20 - std::backtrace_rs::backtrace::libunwind::trace::hb646b3818c959e30
                                       at /cygdrive/d/a/scallywag/rust/rust-1.91.0-1.x86_64/src/rustc-1.91.0-src/library/std/src/../../backtrace/src/backtrace/libunwind.rs:117:9
           1:        0x100460b20 - std::backtrace_rs::backtrace::trace_unsynchronized::hccaef05b188d129d
                                       at /cygdrive/d/a/scallywag/rust/rust-1.91.0-1.x86_64/src/rustc-1.91.0-src/library/std/src/../../backtrace/src/backtrace/mod.rs:66:14
           2:        0x100460b20 - std::sys::backtrace::_print_fmt::h125f99c616e9f9a8
                                       at /cygdrive/d/a/scallywag/rust/rust-1.91.0-1.x86_64/src/rustc-1.91.0-src/library/std/src/sys/backtrace.rs:66:9
           3:        0x100460b20 - <std::sys::backtrace::BacktraceLock::print::DisplayBacktrace as core::fmt::Display>::fmt::ha6ddd3ae47888e14
                                       at /cygdrive/d/a/scallywag/rust/rust-1.91.0-1.x86_64/src/rustc-1.91.0-src/library/std/src/sys/backtrace.rs:39:26
           4:        0x10048f31a - core::fmt::rt::Argument::fmt::h00686ef01f35f425
                                       at /cygdrive/d/a/scallywag/rust/rust-1.91.0-1.x86_64/src/rustc-1.91.0-src/library/core/src/fmt/rt.rs:173:76
           5:        0x10048f31a - core::fmt::write::hafb6881693bf3ac2
                                       at /cygdrive/d/a/scallywag/rust/rust-1.91.0-1.x86_64/src/rustc-1.91.0-src/library/core/src/fmt/mod.rs:1468:25
           6:        0x10041a86f - std::io::default_write_fmt::h4dab8dfbed8868d4
                                       at /cygdrive/d/a/scallywag/rust/rust-1.91.0-1.x86_64/src/rustc-1.91.0-src/library/std/src/io/mod.rs:639:11
           7:        0x10041a86f - std::io::Write::write_fmt::h6edf97c3b63c3bce
                                       at /cygdrive/d/a/scallywag/rust/rust-1.91.0-1.x86_64/src/rustc-1.91.0-src/library/std/src/io/mod.rs:1954:13
           8:        0x10042c255 - std::sys::backtrace::BacktraceLock::print::hd2c616b84c76485c
                                       at /cygdrive/d/a/scallywag/rust/rust-1.91.0-1.x86_64/src/rustc-1.91.0-src/library/std/src/sys/backtrace.rs:42:9
           9:        0x100433d12 - std::panicking::default_hook::{{closure}}::h6da411585cd73d3b
                                       at /cygdrive/d/a/scallywag/rust/rust-1.91.0-1.x86_64/src/rustc-1.91.0-src/library/std/src/panicking.rs:301:27
          10:        0x100433b8a - std::panicking::default_hook::h8cc9d3cc33951cab
                                       at /cygdrive/d/a/scallywag/rust/rust-1.91.0-1.x86_64/src/rustc-1.91.0-src/library/std/src/panicking.rs:328:9
          11:        0x1004344d7 - std::panicking::panic_with_hook::h4312c31a5a302915
                                       at /cygdrive/d/a/scallywag/rust/rust-1.91.0-1.x86_64/src/rustc-1.91.0-src/library/std/src/panicking.rs:834:13
          12:        0x1004342a2 - std::panicking::panic_handler::{{closure}}::hd9bcf2a0d94c90cb
                                       at /cygdrive/d/a/scallywag/rust/rust-1.91.0-1.x86_64/src/rustc-1.91.0-src/library/std/src/panicking.rs:707:13
          13:        0x10042c38f - std::sys::backtrace::__rust_end_short_backtrace::hf2f69349f5fedde2
                                       at /cygdrive/d/a/scallywag/rust/rust-1.91.0-1.x86_64/src/rustc-1.91.0-src/library/std/src/sys/backtrace.rs:174:18
          14:        0x10041203e - __rustc[bb0b2f28308e8f2c]::rust_begin_unwind
                                       at /cygdrive/d/a/scallywag/rust/rust-1.91.0-1.x86_64/src/rustc-1.91.0-src/library/std/src/panicking.rs:698:5
          15:        0x10049fc71 - core::panicking::panic_fmt::h4fdf6c90c527357e
                                       at /cygdrive/d/a/scallywag/rust/rust-1.91.0-1.x86_64/src/rustc-1.91.0-src/library/core/src/panicking.rs:75:14
          16:        0x100402375 - build_script_build::main::{{closure}}::h9b09661ee805f8eb
                                       at /home/drbean/.cargo/registry/src/index.crates.io-1949cf8c6b5b557f/target-lexicon-0.13.2/build.rs:52:54
          17:        0x10040bdae - core::result::Result<T,E>::unwrap_or_else::hde682de2de6c2c40
                                       at /cygdrive/d/a/scallywag/rust/rust-1.91.0-1.x86_64/src/rustc-1.91.0-src/library/core/src/result.rs:1615:23
          18:        0x10040213d - build_script_build::main::h3471bd3a69afb0f6
                                       at /home/drbean/.cargo/registry/src/index.crates.io-1949cf8c6b5b557f/target-lexicon-0.13.2/build.rs:52:35
          19:        0x10040a51b - core::ops::function::FnOnce::call_once::h0752857881febfc5
                                       at /cygdrive/d/a/scallywag/rust/rust-1.91.0-1.x86_64/src/rustc-1.91.0-src/library/core/src/ops/function.rs:250:5
          20:        0x100409f2e - std::sys::backtrace::__rust_begin_short_backtrace::hc45b17075d48ad69
                                       at /cygdrive/d/a/scallywag/rust/rust-1.91.0-1.x86_64/src/rustc-1.91.0-src/library/std/src/sys/backtrace.rs:158:18
          21:        0x100402771 - std::rt::lang_start::{{closure}}::hc389f9dae62d10bf
                                       at /cygdrive/d/a/scallywag/rust/rust-1.91.0-1.x86_64/src/rustc-1.91.0-src/library/std/src/rt.rs:206:18
          22:        0x10041e1b5 - core::ops::function::impls::<impl core::ops::function::FnOnce<A> for &F>::call_once::hc60b0456de58364d
                                       at /cygdrive/d/a/scallywag/rust/rust-1.91.0-1.x86_64/src/rustc-1.91.0-src/library/core/src/ops/function.rs:287:21
          23:        0x10041e1b5 - std::panicking::catch_unwind::do_call::h2e5898e688b1a50b
                                       at /cygdrive/d/a/scallywag/rust/rust-1.91.0-1.x86_64/src/rustc-1.91.0-src/library/std/src/panicking.rs:590:40
          24:        0x10041e1b5 - std::panicking::catch_unwind::h7f62609155fe9d0e
                                       at /cygdrive/d/a/scallywag/rust/rust-1.91.0-1.x86_64/src/rustc-1.91.0-src/library/std/src/panicking.rs:553:19
          25:        0x10041e1b5 - std::panic::catch_unwind::h0ba95c81ca504784
                                       at /cygdrive/d/a/scallywag/rust/rust-1.91.0-1.x86_64/src/rustc-1.91.0-src/library/std/src/panic.rs:359:14
          26:        0x10041e1b5 - std::rt::lang_start_internal::{{closure}}::h0c3db5bbfb345efc
                                       at /cygdrive/d/a/scallywag/rust/rust-1.91.0-1.x86_64/src/rustc-1.91.0-src/library/std/src/rt.rs:175:24
          27:        0x10041e1b5 - std::panicking::catch_unwind::do_call::h63c21c83bfb6e719
                                       at /cygdrive/d/a/scallywag/rust/rust-1.91.0-1.x86_64/src/rustc-1.91.0-src/library/std/src/panicking.rs:590:40
          28:        0x10041e1b5 - std::panicking::catch_unwind::h0d97b5c5b15613b0
                                       at /cygdrive/d/a/scallywag/rust/rust-1.91.0-1.x86_64/src/rustc-1.91.0-src/library/std/src/panicking.rs:553:19
          29:        0x10041e1b5 - std::panic::catch_unwind::h8fbdd35aeccb7f71
                                       at /cygdrive/d/a/scallywag/rust/rust-1.91.0-1.x86_64/src/rustc-1.91.0-src/library/std/src/panic.rs:359:14
          30:        0x10041e1b5 - std::rt::lang_start_internal::h9c9e175168bee11c
                                       at /cygdrive/d/a/scallywag/rust/rust-1.91.0-1.x86_64/src/rustc-1.91.0-src/library/std/src/rt.rs:171:5
          31:        0x10040275a - std::rt::lang_start::hd92f0fe6ad35a7be
                                       at /cygdrive/d/a/scallywag/rust/rust-1.91.0-1.x86_64/src/rustc-1.91.0-src/library/std/src/rt.rs:205:5
          32:        0x1004095ef - main
          33:     0x7ffb7d4980f3 - <unknown>
          34:     0x7ffb7d495cd5 - <unknown>
          35:     0x7ffb7d495d8b - <unknown>
          36:                0x0 - <unknown>
      warning: build failed, waiting for other jobs to finish...
      💥 maturin failed
        Caused by: Failed to build a native library through cargo
        Caused by: Cargo build finished with "exit status: 101": `env -u CARGO PYO3_BUILD_EXTENSION_MODULE="1" PYO3_ENVIRONMENT_SIGNATURE="cpython-3.12-64bit" PYO3_PYTHON="/home/drbean/dot/browser/tooi/.venv.312/bin/python3" PYTHON_SYS_EXECUTABLE="/home/drbean/dot/browser/tooi/.venv.312/bin/python3" "cargo" "rustc" "--profile" "release" "--message-format" "json-render-diagnostics" "--manifest-path" "/tmp/pip-install-s56o7awx/pydantic-core_db6fcc382f8942f1b53e915621dc0eb1/Cargo.toml" "--lib" "--crate-type" "cdylib"`
      Error: command ['maturin', 'pep517', 'build-wheel', '-i', '/home/drbean/dot/browser/tooi/.venv.312/bin/python3', '--compatibility', 'off'] returned non-zero exit status 1
      [end of output]


-- 
Greg "Dr Bean" Matheson		Academic politics is so bitter because the stakes
http://drbean.sdf.org		are so small.
[email protected]		--Wallace S Sayre
				

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