target_spec_json/
lib.rs

1// SPDX-License-Identifier: Apache-2.0 OR MIT
2
3/*!
4<!-- Note: Document from sync-markdown-to-rustdoc:start through sync-markdown-to-rustdoc:end
5     is synchronized from README.md. Any changes to that range are not preserved. -->
6<!-- tidy:sync-markdown-to-rustdoc:start -->
7
8Structured access to rustc `--print target-spec-json` and `--print all-target-specs-json`.
9
10## Usage
11
12Add this to your `Cargo.toml`:
13
14```toml
15[dependencies]
16target-spec-json = "0.2"
17```
18
19## Compatibility
20
21Both `--print target-spec-json` and `--print all-target-specs-json` are unstable interfaces and may not work with certain version combinations of Rust versions and `target-spec-json` versions.
22
23The following combinations have been confirmed to work:
24
25| target-spec-json | Rust                                    |
26| ---------------- | --------------------------------------- |
27| 0.2.7            | nightly-2026-01-09                      |
28| 0.2.6            | nightly-2025-11-29 - nightly-2026-01-08 |
29| 0.2.5            | nightly-2025-10-08 - nightly-2025-10-30 |
30| 0.2.4            | nightly-2025-09-23 - nightly-2025-10-07 |
31| 0.2.3            | nightly-2025-09-01 - nightly-2025-09-22 |
32| 0.2.2            | nightly-2025-08-31                      |
33| 0.2.1            | nightly-2025-08-10 - nightly-2025-08-30 |
34| 0.2.0            | nightly-2025-07-06 - nightly-2025-08-08 |
35
36## Related Projects
37
38- [cargo-config2]: Library to load and resolve Cargo configuration.
39
40[cargo-config2]: https://github.com/taiki-e/cargo-config2
41
42<!-- tidy:sync-markdown-to-rustdoc:end -->
43*/
44
45#![no_std]
46#![doc(test(
47    no_crate_inject,
48    attr(allow(
49        dead_code,
50        unused_variables,
51        clippy::undocumented_unsafe_blocks,
52        clippy::unused_trait_names,
53    ))
54))]
55#![forbid(unsafe_code)]
56#![warn(
57    // Lints that may help when writing public library.
58    missing_debug_implementations,
59    // missing_docs,
60    clippy::alloc_instead_of_core,
61    clippy::exhaustive_enums,
62    clippy::exhaustive_structs,
63    clippy::impl_trait_in_params,
64    clippy::std_instead_of_alloc,
65    clippy::std_instead_of_core,
66    // clippy::missing_inline_in_public_items,
67)]
68
69extern crate alloc;
70extern crate std;
71
72#[cfg(test)]
73#[path = "gen/tests/assert_impl.rs"]
74mod assert_impl;
75#[cfg(test)]
76#[path = "gen/tests/track_size.rs"]
77mod track_size;
78
79#[path = "gen/target_spec.rs"]
80mod target_spec;
81pub use self::target_spec::{
82    Arch, BinaryFormat, Env, Os, PanicStrategy, Sanitizer, TargetEndian, TargetFamily,
83};
84
85#[macro_use]
86mod process;
87
88mod error;
89
90use alloc::{collections::BTreeMap, string::String, vec::Vec};
91use core::ops;
92use std::process::Command;
93
94use serde_derive::{Deserialize, Serialize};
95
96pub use self::error::Error;
97use self::{error::Result, process::ProcessBuilder};
98
99pub type AllTargetSpecs = BTreeMap<String, TargetSpec>;
100
101// Refs:
102// - https://github.com/rust-lang/rust/blob/HEAD/compiler/rustc_target/src/spec/mod.rs
103// - https://github.com/rust-lang/rust/blob/c0bb3b98bb7aac24a37635e5d36d961e0b14f435/compiler/rustc_target/src/spec/json.rs
104// TODO: use https://github.com/rust-lang/rust/pull/144498
105
106#[derive(Debug, Clone, Serialize, Deserialize)]
107#[serde(rename_all = "kebab-case")]
108#[cfg_attr(test, serde(deny_unknown_fields))]
109#[non_exhaustive]
110pub struct TargetSpec {
111    #[serde(skip_serializing_if = "Option::is_none")]
112    pub abi_return_struct_as_int: Option<bool>,
113    #[serde(skip_serializing_if = "Option::is_none")]
114    pub abi: Option<String>,
115    #[serde(skip_serializing_if = "Option::is_none")]
116    pub allows_weak_linkage: Option<bool>,
117    pub arch: Arch,
118    #[serde(skip_serializing_if = "Option::is_none")]
119    pub archive_format: Option<String>,
120    #[serde(skip_serializing_if = "Option::is_none")]
121    pub asm_args: Option<Vec<String>>,
122    #[serde(default = "default_true", skip_serializing_if = "Clone::clone")]
123    pub atomic_cas: bool,
124    #[serde(default, skip_serializing_if = "BinaryFormat::is_elf")]
125    pub binary_format: BinaryFormat,
126    #[serde(skip_serializing_if = "Option::is_none")]
127    pub bitcode_llvm_cmdline: Option<String>,
128    #[serde(skip_serializing_if = "Option::is_none")]
129    pub c_enum_min_bits: Option<u32>,
130    #[serde(skip_serializing_if = "Option::is_none")]
131    pub code_model: Option<String>,
132    #[serde(skip_serializing_if = "Option::is_none")]
133    pub cpu: Option<String>,
134    #[serde(skip_serializing_if = "Option::is_none")]
135    pub crt_objects_fallback: Option<String>,
136    #[serde(skip_serializing_if = "Option::is_none")]
137    pub crt_static_allows_dylibs: Option<bool>,
138    #[serde(skip_serializing_if = "Option::is_none")]
139    pub crt_static_default: Option<bool>,
140    #[serde(skip_serializing_if = "Option::is_none")]
141    pub crt_static_respected: Option<bool>,
142    pub data_layout: String,
143    #[serde(skip_serializing_if = "Option::is_none")]
144    pub debuginfo_kind: Option<String>,
145    #[serde(skip_serializing_if = "Option::is_none")]
146    pub default_adjusted_cabi: Option<String>,
147    #[serde(skip_serializing_if = "Option::is_none")]
148    pub default_codegen_units: Option<u32>,
149    #[serde(skip_serializing_if = "Option::is_none")]
150    pub default_dwarf_version: Option<u32>,
151    #[serde(skip_serializing_if = "Option::is_none")]
152    pub default_hidden_visibility: Option<bool>,
153    #[serde(skip_serializing_if = "Option::is_none")]
154    pub default_sanitizers: Option<Vec<Sanitizer>>,
155    #[serde(skip_serializing_if = "Option::is_none")]
156    pub default_uwtable: Option<bool>,
157    #[serde(skip_serializing_if = "Option::is_none")]
158    pub direct_access_external_data: Option<bool>,
159    #[serde(skip_serializing_if = "Option::is_none")]
160    pub disable_redzone: Option<bool>,
161    #[serde(skip_serializing_if = "Option::is_none")]
162    pub dll_prefix: Option<String>,
163    #[serde(skip_serializing_if = "Option::is_none")]
164    pub dll_suffix: Option<String>,
165    #[serde(skip_serializing_if = "Option::is_none")]
166    pub dll_tls_export: Option<bool>,
167    #[serde(skip_serializing_if = "Option::is_none")]
168    pub dynamic_linking: Option<bool>,
169    #[serde(skip_serializing_if = "Option::is_none")]
170    pub eh_frame_header: Option<bool>,
171    #[serde(skip_serializing_if = "Option::is_none")]
172    pub emit_debug_gdb_scripts: Option<bool>,
173    #[serde(skip_serializing_if = "Option::is_none")]
174    pub entry_abi: Option<String>,
175    #[serde(skip_serializing_if = "Option::is_none")]
176    pub entry_name: Option<String>,
177    #[serde(default, skip_serializing_if = "Env::is_none")]
178    pub env: Env,
179    #[serde(skip_serializing_if = "Option::is_none")]
180    pub executables: Option<bool>,
181    #[serde(skip_serializing_if = "Option::is_none")]
182    pub exe_suffix: Option<String>,
183    #[serde(skip_serializing_if = "Option::is_none")]
184    pub features: Option<String>,
185    #[serde(skip_serializing_if = "Option::is_none")]
186    pub force_emulated_tls: Option<bool>,
187    #[serde(skip_serializing_if = "Option::is_none")]
188    pub forces_embed_bitcode: Option<bool>,
189    #[serde(skip_serializing_if = "Option::is_none")]
190    pub frame_pointer: Option<String>,
191    #[serde(skip_serializing_if = "Option::is_none")]
192    pub function_sections: Option<bool>,
193    #[serde(skip_serializing_if = "Option::is_none")]
194    pub generate_arange_section: Option<bool>,
195    #[serde(skip_serializing_if = "Option::is_none")]
196    pub has_rpath: Option<bool>,
197    #[serde(skip_serializing_if = "Option::is_none")]
198    pub has_thread_local: Option<bool>,
199    #[serde(default, skip_serializing_if = "ops::Not::not")]
200    pub has_thumb_interworking: bool,
201    #[serde(default, skip_serializing_if = "ops::Not::not")]
202    pub is_builtin: bool,
203    #[serde(default, skip_serializing_if = "ops::Not::not")]
204    pub is_like_android: bool,
205    #[serde(default, skip_serializing_if = "ops::Not::not")]
206    pub is_like_aix: bool,
207    #[serde(default, skip_serializing_if = "ops::Not::not")]
208    pub is_like_darwin: bool,
209    #[serde(default, skip_serializing_if = "ops::Not::not")]
210    pub is_like_gpu: bool,
211    /// replaced by `is_like_darwin`
212    #[serde(default, skip_serializing_if = "ops::Not::not")]
213    pub is_like_osx: bool,
214    #[serde(default, skip_serializing_if = "ops::Not::not")]
215    pub is_like_solaris: bool,
216    #[serde(default, skip_serializing_if = "ops::Not::not")]
217    pub is_like_msvc: bool,
218    #[serde(default, skip_serializing_if = "ops::Not::not")]
219    pub is_like_vexos: bool,
220    #[serde(default, skip_serializing_if = "ops::Not::not")]
221    pub is_like_wasm: bool,
222    #[serde(default, skip_serializing_if = "ops::Not::not")]
223    pub is_like_windows: bool,
224    #[serde(skip_serializing_if = "Option::is_none")]
225    pub late_link_args: Option<BTreeMap<String, Vec<String>>>,
226    #[serde(skip_serializing_if = "Option::is_none")]
227    pub late_link_args_dynamic: Option<BTreeMap<String, Vec<String>>>,
228    #[serde(skip_serializing_if = "Option::is_none")]
229    pub late_link_args_static: Option<BTreeMap<String, Vec<String>>>,
230    #[serde(skip_serializing_if = "Option::is_none")]
231    pub limit_rdylib_exports: Option<bool>,
232    #[serde(skip_serializing_if = "Option::is_none")]
233    pub link_env: Option<Vec<String>>,
234    #[serde(skip_serializing_if = "Option::is_none")]
235    pub link_env_remove: Option<Vec<String>>,
236    #[serde(skip_serializing_if = "Option::is_none")]
237    pub link_self_contained: Option<BTreeMap<String, Vec<String>>>,
238    #[serde(skip_serializing_if = "Option::is_none")]
239    pub link_script: Option<String>,
240    #[serde(skip_serializing_if = "Option::is_none")]
241    pub linker: Option<String>,
242    #[serde(skip_serializing_if = "Option::is_none")]
243    pub linker_flavor: Option<String>,
244    #[serde(skip_serializing_if = "Option::is_none")]
245    pub linker_is_gnu: Option<bool>,
246    #[serde(skip_serializing_if = "Option::is_none")]
247    pub lld_flavor: Option<String>,
248    #[serde(skip_serializing_if = "Option::is_none")]
249    pub llvm_abiname: Option<String>,
250    #[serde(skip_serializing_if = "Option::is_none")]
251    pub llvm_args: Option<Vec<String>>,
252    #[serde(skip_serializing_if = "Option::is_none")]
253    pub llvm_floatabi: Option<String>,
254    #[serde(skip_serializing_if = "Option::is_none")]
255    pub llvm_mcount_intrinsic: Option<String>,
256    pub llvm_target: String,
257    #[serde(skip_serializing_if = "Option::is_none")]
258    pub main_needs_argc_argv: Option<bool>,
259    #[serde(skip_serializing_if = "Option::is_none")]
260    pub max_atomic_width: Option<u32>,
261    #[serde(skip_serializing_if = "Option::is_none")]
262    pub merge_functions: Option<String>,
263    pub metadata: Option<Metadata>,
264    #[serde(skip_serializing_if = "Option::is_none")]
265    pub min_atomic_width: Option<u32>,
266    #[serde(skip_serializing_if = "Option::is_none")]
267    pub min_global_align: Option<u32>,
268    #[serde(skip_serializing_if = "Option::is_none")]
269    pub need_explicit_cpu: Option<bool>,
270    #[serde(skip_serializing_if = "Option::is_none")]
271    pub needs_plt: Option<bool>,
272    #[serde(skip_serializing_if = "Option::is_none")]
273    pub no_builtins: Option<bool>,
274    #[serde(skip_serializing_if = "Option::is_none")]
275    pub no_default_libraries: Option<bool>,
276    #[serde(default, skip_serializing_if = "Os::is_none")]
277    pub os: Os,
278    #[serde(skip_serializing_if = "Option::is_none")]
279    pub obj_is_bitcode: Option<bool>,
280    #[serde(skip_serializing_if = "Option::is_none")]
281    pub only_cdylib: Option<bool>,
282    #[serde(skip_serializing_if = "Option::is_none")]
283    pub override_export_symbols: Option<Vec<String>>,
284    #[serde(default, skip_serializing_if = "PanicStrategy::is_unwind")]
285    pub panic_strategy: PanicStrategy,
286    #[serde(skip_serializing_if = "Option::is_none")]
287    pub plt_by_default: Option<bool>,
288    #[serde(skip_serializing_if = "Option::is_none")]
289    pub position_independent_executables: Option<bool>,
290    #[serde(skip_serializing_if = "Option::is_none")]
291    pub post_link_args: Option<BTreeMap<String, Vec<String>>>,
292    #[serde(skip_serializing_if = "Option::is_none")]
293    pub post_link_objects: Option<BTreeMap<String, Vec<String>>>,
294    #[serde(skip_serializing_if = "Option::is_none")]
295    pub post_link_objects_fallback: Option<BTreeMap<String, Vec<String>>>,
296    #[serde(skip_serializing_if = "Option::is_none")]
297    pub pre_link_args: Option<BTreeMap<String, Vec<String>>>,
298    #[serde(skip_serializing_if = "Option::is_none")]
299    pub pre_link_objects: Option<BTreeMap<String, Vec<String>>>,
300    #[serde(skip_serializing_if = "Option::is_none")]
301    pub pre_link_objects_fallback: Option<BTreeMap<String, Vec<String>>>,
302    #[serde(skip_serializing_if = "Option::is_none")]
303    pub relax_elf_relocations: Option<bool>,
304    #[serde(skip_serializing_if = "Option::is_none")]
305    pub relocation_model: Option<String>,
306    #[serde(skip_serializing_if = "Option::is_none")]
307    pub relro_level: Option<String>,
308    #[serde(skip_serializing_if = "Option::is_none")]
309    pub requires_lto: Option<bool>,
310    #[serde(skip_serializing_if = "Option::is_none")]
311    pub requires_uwtable: Option<bool>,
312    #[serde(skip_serializing_if = "Option::is_none")]
313    pub rustc_abi: Option<String>,
314    #[serde(skip_serializing_if = "Option::is_none")]
315    pub split_debuginfo: Option<String>,
316    #[serde(skip_serializing_if = "Option::is_none")]
317    pub stack_probes: Option<StackProbes>,
318    #[serde(skip_serializing_if = "Option::is_none")]
319    pub static_initializer_must_be_acyclic: Option<bool>,
320    #[serde(skip_serializing_if = "Option::is_none")]
321    pub static_position_independent_executables: Option<bool>,
322    #[serde(skip_serializing_if = "Option::is_none")]
323    pub staticlib_prefix: Option<String>,
324    #[serde(skip_serializing_if = "Option::is_none")]
325    pub staticlib_suffix: Option<String>,
326    #[serde(default, skip_serializing_if = "Vec::is_empty")]
327    pub supported_sanitizers: Vec<Sanitizer>,
328    #[serde(default, skip_serializing_if = "Vec::is_empty")]
329    pub supported_split_debuginfo: Vec<String>,
330    #[serde(default = "default_true", skip_serializing_if = "Clone::clone")]
331    pub supports_stack_protector: bool,
332    #[serde(default, skip_serializing_if = "ops::Not::not")]
333    pub supports_xray: bool,
334    #[serde(skip_serializing_if = "Option::is_none")]
335    pub simd_types_indirect: Option<bool>,
336    #[serde(default, skip_serializing_if = "ops::Not::not")]
337    pub singlethread: bool,
338    #[serde(default, skip_serializing_if = "TargetEndian::is_little")]
339    pub target_endian: TargetEndian,
340    #[serde(default, skip_serializing_if = "Vec::is_empty")]
341    pub target_family: Vec<TargetFamily>,
342    #[serde(skip_serializing_if = "Option::is_none")]
343    pub target_mcount: Option<String>,
344    // Integer since 1.89
345    #[serde(skip_serializing_if = "Option::is_none")]
346    pub target_c_int_width: Option<u32>,
347    // Integer since 1.91
348    pub target_pointer_width: u32,
349    #[serde(skip_serializing_if = "Option::is_none")]
350    pub tls_model: Option<String>,
351    #[serde(skip_serializing_if = "Option::is_none")]
352    pub trap_unreachable: Option<bool>,
353    #[serde(skip_serializing_if = "Option::is_none")]
354    pub use_ctors_section: Option<bool>,
355    #[serde(skip_serializing_if = "Option::is_none")]
356    pub vendor: Option<String>,
357}
358
359#[derive(Debug, Clone, Serialize, Deserialize)]
360#[cfg_attr(test, serde(deny_unknown_fields))]
361#[non_exhaustive]
362pub struct Metadata {
363    pub description: Option<String>,
364    pub host_tools: Option<bool>,
365    pub std: Option<bool>,
366    pub tier: Option<u32>,
367}
368
369#[derive(Debug, Clone, Serialize, Deserialize)]
370#[serde(rename_all = "kebab-case")]
371#[cfg_attr(test, serde(deny_unknown_fields))]
372#[non_exhaustive]
373pub struct StackProbes {
374    pub kind: String,
375    #[serde(skip_serializing_if = "Option::is_none")]
376    pub min_llvm_version_for_inline: Option<(u32, u32, u32)>,
377}
378
379fn default_true() -> bool {
380    true
381}
382
383/// `<rustc> -Z unstable-options --print target-spec-json --target <target>`
384pub fn target_spec_json(rustc: Command, target: &str) -> Result<TargetSpec> {
385    let raw = ProcessBuilder::from_std(rustc)
386        .args(["-Z", "unstable-options", "--print", "target-spec-json", "--target", target])
387        .read()?;
388    serde_json::from_str(&raw).map_err(Error::new)
389}
390
391/// `<rustc> -Z unstable-options --print all-target-specs-json`
392pub fn all_target_specs_json(rustc: Command) -> Result<AllTargetSpecs> {
393    let raw = ProcessBuilder::from_std(rustc)
394        .args(["-Z", "unstable-options", "--print", "all-target-specs-json"])
395        .read()?;
396    serde_json::from_str(&raw).map_err(Error::new)
397}
398
399#[cfg(test)]
400mod tests {
401    use std::eprintln;
402
403    use super::*;
404
405    fn target_spec_json(target: &str) -> Result<(TargetSpec, String)> {
406        let mut cmd = cmd!(
407            "rustc",
408            "-Z",
409            "unstable-options",
410            "--print",
411            "target-spec-json",
412            "--target",
413            target
414        );
415        if !rustversion::cfg!(nightly) {
416            cmd.env("RUSTC_BOOTSTRAP", "1");
417        }
418        let raw = cmd.read()?;
419        Ok((serde_json::from_str(&raw).map_err(Error::new)?, raw))
420    }
421
422    fn all_target_specs_json() -> Result<(AllTargetSpecs, String)> {
423        let mut cmd = cmd!("rustc", "-Z", "unstable-options", "--print", "all-target-specs-json");
424        if !rustversion::cfg!(nightly) {
425            cmd.env("RUSTC_BOOTSTRAP", "1");
426        }
427        let raw = cmd.read()?;
428        Ok((serde_json::from_str(&raw).map_err(Error::new)?, raw))
429    }
430
431    // Skip pre-1.91 because target-pointer-width change
432    #[rustversion::attr(before(1.91), ignore)]
433    #[test]
434    #[cfg_attr(miri, ignore)] // Miri doesn't support std::process::Command: https://github.com/rust-lang/miri/issues/3374
435    fn parse_target_spec_json() {
436        // builtin targets
437        for target in cmd!("rustc", "--print", "target-list").read().unwrap().lines() {
438            eprintln!("target={target}:");
439            let (parsed, raw) = target_spec_json(target).unwrap();
440            let deserialized = serde_json::to_string(&parsed).unwrap();
441            assert_eq!(
442                serde_json::from_str::<serde_json::Value>(&raw).unwrap(),
443                serde_json::from_str::<serde_json::Value>(&deserialized).unwrap()
444            );
445        }
446        eprintln!("all-targets:");
447        let (parsed, raw) = all_target_specs_json().unwrap();
448        let deserialized = serde_json::to_string(&parsed).unwrap();
449        assert_eq!(
450            serde_json::from_str::<serde_json::Value>(&raw).unwrap(),
451            serde_json::from_str::<serde_json::Value>(&deserialized).unwrap()
452        );
453        // TODO: custom targets
454        // for spec_path in fs::read_dir(fixtures_path().join("target-specs"))
455        //     .unwrap()
456        //     .map(|e| e.unwrap().path())
457        // {
458        // }
459    }
460}
target_spec_json/lib.rs

target_spec_json/
lib.rs
