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| 0.2.9            | nightly-2026-04-29                      |
28| 0.2.8            | nightly-2026-03-26 - nightly-2026-04-29 |
29| 0.2.7            | nightly-2026-01-09 - nightly-2026-03-25 |
30| 0.2.6            | nightly-2025-11-29 - nightly-2026-01-08 |
31| 0.2.5            | nightly-2025-10-08 - nightly-2025-10-30 |
32| 0.2.4            | nightly-2025-09-23 - nightly-2025-10-07 |
33| 0.2.3            | nightly-2025-09-01 - nightly-2025-09-22 |
34| 0.2.2            | nightly-2025-08-31                      |
35| 0.2.1            | nightly-2025-08-10 - nightly-2025-08-30 |
36| 0.2.0            | nightly-2025-07-06 - nightly-2025-08-08 |
37
38## Related Projects
39
40- [cargo-config2]: Library to load and resolve Cargo configuration.
41
42[cargo-config2]: https://github.com/taiki-e/cargo-config2
43
44<!-- tidy:sync-markdown-to-rustdoc:end -->
45*/
46
47#![no_std]
48#![doc(test(
49    no_crate_inject,
50    attr(allow(
51        dead_code,
52        unused_variables,
53        clippy::undocumented_unsafe_blocks,
54        clippy::unused_trait_names,
55    ))
56))]
57#![forbid(unsafe_code)]
58#![warn(
59    // Lints that may help when writing public library.
60    missing_debug_implementations,
61    // missing_docs,
62    clippy::alloc_instead_of_core,
63    clippy::exhaustive_enums,
64    clippy::exhaustive_structs,
65    clippy::impl_trait_in_params,
66    clippy::std_instead_of_alloc,
67    clippy::std_instead_of_core,
68    // clippy::missing_inline_in_public_items,
69)]
70
71extern crate alloc;
72extern crate std;
73
74#[cfg(test)]
75#[path = "gen/tests/assert_impl.rs"]
76mod assert_impl;
77#[cfg(test)]
78#[path = "gen/tests/track_size.rs"]
79mod track_size;
80
81#[path = "gen/target_spec.rs"]
82mod target_spec;
83pub use self::target_spec::{
84    Arch, BinaryFormat, Env, Os, PanicStrategy, Sanitizer, TargetEndian, TargetFamily,
85};
86
87#[macro_use]
88mod process;
89
90mod error;
91
92use alloc::{collections::BTreeMap, string::String, vec::Vec};
93use core::ops;
94use std::process::Command;
95
96use serde_derive::{Deserialize, Serialize};
97
98pub use self::error::Error;
99use self::{error::Result, process::ProcessBuilder};
100
101pub type AllTargetSpecs = BTreeMap<String, TargetSpec>;
102
103// Refs:
104// - https://github.com/rust-lang/rust/blob/HEAD/compiler/rustc_target/src/spec/mod.rs
105// - https://github.com/rust-lang/rust/blob/c0bb3b98bb7aac24a37635e5d36d961e0b14f435/compiler/rustc_target/src/spec/json.rs
106// TODO: use https://github.com/rust-lang/rust/pull/144498
107
108#[derive(Debug, Clone, Serialize, Deserialize)]
109#[serde(rename_all = "kebab-case")]
110#[cfg_attr(test, serde(deny_unknown_fields))]
111#[non_exhaustive]
112pub struct TargetSpec {
113    #[serde(skip_serializing_if = "Option::is_none")]
114    pub abi_return_struct_as_int: Option<bool>,
115    #[serde(skip_serializing_if = "Option::is_none")]
116    pub abi: Option<String>,
117    #[serde(skip_serializing_if = "Option::is_none")]
118    pub allows_weak_linkage: Option<bool>,
119    pub arch: Arch,
120    #[serde(skip_serializing_if = "Option::is_none")]
121    pub archive_format: Option<String>,
122    #[serde(skip_serializing_if = "Option::is_none")]
123    pub asm_args: Option<Vec<String>>,
124    #[serde(default = "default_true", skip_serializing_if = "Clone::clone")]
125    pub atomic_cas: bool,
126    #[serde(default, skip_serializing_if = "BinaryFormat::is_elf")]
127    pub binary_format: BinaryFormat,
128    #[serde(skip_serializing_if = "Option::is_none")]
129    pub bitcode_llvm_cmdline: Option<String>,
130    #[serde(skip_serializing_if = "Option::is_none")]
131    pub c_enum_min_bits: Option<u32>,
132    #[serde(skip_serializing_if = "Option::is_none")]
133    pub code_model: Option<String>,
134    #[serde(skip_serializing_if = "Option::is_none")]
135    pub cpu: Option<String>,
136    #[serde(skip_serializing_if = "Option::is_none")]
137    pub crt_objects_fallback: Option<String>,
138    #[serde(skip_serializing_if = "Option::is_none")]
139    pub crt_static_allows_dylibs: Option<bool>,
140    #[serde(skip_serializing_if = "Option::is_none")]
141    pub crt_static_default: Option<bool>,
142    #[serde(skip_serializing_if = "Option::is_none")]
143    pub crt_static_respected: Option<bool>,
144    pub data_layout: String,
145    #[serde(skip_serializing_if = "Option::is_none")]
146    pub debuginfo_kind: Option<String>,
147    #[serde(skip_serializing_if = "Option::is_none")]
148    pub default_adjusted_cabi: Option<String>,
149    #[serde(skip_serializing_if = "Option::is_none")]
150    pub default_codegen_units: Option<u32>,
151    #[serde(skip_serializing_if = "Option::is_none")]
152    pub default_dwarf_version: Option<u32>,
153    #[serde(skip_serializing_if = "Option::is_none")]
154    pub default_hidden_visibility: Option<bool>,
155    #[serde(skip_serializing_if = "Option::is_none")]
156    pub default_sanitizers: Option<Vec<Sanitizer>>,
157    #[serde(skip_serializing_if = "Option::is_none")]
158    pub default_uwtable: Option<bool>,
159    #[serde(skip_serializing_if = "Option::is_none")]
160    pub direct_access_external_data: Option<bool>,
161    #[serde(skip_serializing_if = "Option::is_none")]
162    pub disable_redzone: Option<bool>,
163    #[serde(skip_serializing_if = "Option::is_none")]
164    pub dll_prefix: Option<String>,
165    #[serde(skip_serializing_if = "Option::is_none")]
166    pub dll_suffix: Option<String>,
167    #[serde(skip_serializing_if = "Option::is_none")]
168    pub dll_tls_export: Option<bool>,
169    #[serde(skip_serializing_if = "Option::is_none")]
170    pub dynamic_linking: Option<bool>,
171    #[serde(skip_serializing_if = "Option::is_none")]
172    pub eh_frame_header: Option<bool>,
173    #[serde(skip_serializing_if = "Option::is_none")]
174    pub emit_debug_gdb_scripts: Option<bool>,
175    #[serde(skip_serializing_if = "Option::is_none")]
176    pub entry_abi: Option<String>,
177    #[serde(skip_serializing_if = "Option::is_none")]
178    pub entry_name: Option<String>,
179    #[serde(default, skip_serializing_if = "Env::is_none")]
180    pub env: Env,
181    #[serde(skip_serializing_if = "Option::is_none")]
182    pub executables: Option<bool>,
183    #[serde(skip_serializing_if = "Option::is_none")]
184    pub exe_suffix: Option<String>,
185    #[serde(skip_serializing_if = "Option::is_none")]
186    pub features: Option<String>,
187    #[serde(skip_serializing_if = "Option::is_none")]
188    pub force_emulated_tls: Option<bool>,
189    #[serde(skip_serializing_if = "Option::is_none")]
190    pub forces_embed_bitcode: Option<bool>,
191    #[serde(skip_serializing_if = "Option::is_none")]
192    pub frame_pointer: Option<String>,
193    #[serde(skip_serializing_if = "Option::is_none")]
194    pub function_sections: Option<bool>,
195    #[serde(skip_serializing_if = "Option::is_none")]
196    pub generate_arange_section: Option<bool>,
197    #[serde(skip_serializing_if = "Option::is_none")]
198    pub has_rpath: Option<bool>,
199    #[serde(skip_serializing_if = "Option::is_none")]
200    pub has_thread_local: Option<bool>,
201    #[serde(default, skip_serializing_if = "ops::Not::not")]
202    pub has_thumb_interworking: bool,
203    #[serde(default, skip_serializing_if = "ops::Not::not")]
204    pub is_builtin: bool,
205    #[serde(default, skip_serializing_if = "ops::Not::not")]
206    pub is_like_android: bool,
207    #[serde(default, skip_serializing_if = "ops::Not::not")]
208    pub is_like_aix: bool,
209    #[serde(default, skip_serializing_if = "ops::Not::not")]
210    pub is_like_darwin: bool,
211    #[serde(default, skip_serializing_if = "ops::Not::not")]
212    pub is_like_gpu: bool,
213    /// replaced by `is_like_darwin`
214    #[serde(default, skip_serializing_if = "ops::Not::not")]
215    pub is_like_osx: bool,
216    #[serde(default, skip_serializing_if = "ops::Not::not")]
217    pub is_like_solaris: bool,
218    #[serde(default, skip_serializing_if = "ops::Not::not")]
219    pub is_like_msvc: bool,
220    #[serde(default, skip_serializing_if = "ops::Not::not")]
221    pub is_like_vexos: bool,
222    #[serde(default, skip_serializing_if = "ops::Not::not")]
223    pub is_like_wasm: bool,
224    #[serde(default, skip_serializing_if = "ops::Not::not")]
225    pub is_like_windows: bool,
226    #[serde(skip_serializing_if = "Option::is_none")]
227    pub late_link_args: Option<BTreeMap<String, Vec<String>>>,
228    #[serde(skip_serializing_if = "Option::is_none")]
229    pub late_link_args_dynamic: Option<BTreeMap<String, Vec<String>>>,
230    #[serde(skip_serializing_if = "Option::is_none")]
231    pub late_link_args_static: Option<BTreeMap<String, Vec<String>>>,
232    #[serde(skip_serializing_if = "Option::is_none")]
233    pub limit_rdylib_exports: Option<bool>,
234    #[serde(skip_serializing_if = "Option::is_none")]
235    pub link_env: Option<Vec<String>>,
236    #[serde(skip_serializing_if = "Option::is_none")]
237    pub link_env_remove: Option<Vec<String>>,
238    #[serde(skip_serializing_if = "Option::is_none")]
239    pub link_self_contained: Option<BTreeMap<String, Vec<String>>>,
240    #[serde(skip_serializing_if = "Option::is_none")]
241    pub link_script: Option<String>,
242    #[serde(skip_serializing_if = "Option::is_none")]
243    pub linker: Option<String>,
244    #[serde(skip_serializing_if = "Option::is_none")]
245    pub linker_flavor: Option<String>,
246    #[serde(skip_serializing_if = "Option::is_none")]
247    pub linker_is_gnu: Option<bool>,
248    #[serde(skip_serializing_if = "Option::is_none")]
249    pub lld_flavor: Option<String>,
250    #[serde(skip_serializing_if = "Option::is_none")]
251    pub llvm_abiname: Option<String>,
252    #[serde(skip_serializing_if = "Option::is_none")]
253    pub llvm_args: Option<Vec<String>>,
254    #[serde(skip_serializing_if = "Option::is_none")]
255    pub llvm_floatabi: Option<String>,
256    #[serde(skip_serializing_if = "Option::is_none")]
257    pub llvm_mcount_intrinsic: Option<String>,
258    pub llvm_target: String,
259    #[serde(skip_serializing_if = "Option::is_none")]
260    pub main_needs_argc_argv: Option<bool>,
261    #[serde(skip_serializing_if = "Option::is_none")]
262    pub max_atomic_width: Option<u32>,
263    #[serde(skip_serializing_if = "Option::is_none")]
264    pub merge_functions: Option<String>,
265    pub metadata: Option<Metadata>,
266    #[serde(skip_serializing_if = "Option::is_none")]
267    pub min_atomic_width: Option<u32>,
268    #[serde(skip_serializing_if = "Option::is_none")]
269    pub min_global_align: Option<u32>,
270    #[serde(skip_serializing_if = "Option::is_none")]
271    pub need_explicit_cpu: Option<bool>,
272    #[serde(skip_serializing_if = "Option::is_none")]
273    pub needs_plt: Option<bool>,
274    #[serde(skip_serializing_if = "Option::is_none")]
275    pub no_builtins: Option<bool>,
276    #[serde(skip_serializing_if = "Option::is_none")]
277    pub no_default_libraries: Option<bool>,
278    #[serde(default, skip_serializing_if = "Os::is_none")]
279    pub os: Os,
280    #[serde(skip_serializing_if = "Option::is_none")]
281    pub obj_is_bitcode: Option<bool>,
282    #[serde(skip_serializing_if = "Option::is_none")]
283    pub only_cdylib: Option<bool>,
284    #[serde(skip_serializing_if = "Option::is_none")]
285    pub override_export_symbols: Option<Vec<String>>,
286    #[serde(default, skip_serializing_if = "PanicStrategy::is_unwind")]
287    pub panic_strategy: PanicStrategy,
288    #[serde(skip_serializing_if = "Option::is_none")]
289    pub plt_by_default: Option<bool>,
290    #[serde(skip_serializing_if = "Option::is_none")]
291    pub position_independent_executables: Option<bool>,
292    #[serde(skip_serializing_if = "Option::is_none")]
293    pub post_link_args: Option<BTreeMap<String, Vec<String>>>,
294    #[serde(skip_serializing_if = "Option::is_none")]
295    pub post_link_objects: Option<BTreeMap<String, Vec<String>>>,
296    #[serde(skip_serializing_if = "Option::is_none")]
297    pub post_link_objects_fallback: Option<BTreeMap<String, Vec<String>>>,
298    #[serde(skip_serializing_if = "Option::is_none")]
299    pub pre_link_args: Option<BTreeMap<String, Vec<String>>>,
300    #[serde(skip_serializing_if = "Option::is_none")]
301    pub pre_link_objects: Option<BTreeMap<String, Vec<String>>>,
302    #[serde(skip_serializing_if = "Option::is_none")]
303    pub pre_link_objects_fallback: Option<BTreeMap<String, Vec<String>>>,
304    #[serde(skip_serializing_if = "Option::is_none")]
305    pub relax_elf_relocations: Option<bool>,
306    #[serde(skip_serializing_if = "Option::is_none")]
307    pub relocation_model: Option<String>,
308    #[serde(skip_serializing_if = "Option::is_none")]
309    pub relro_level: Option<String>,
310    #[serde(skip_serializing_if = "Option::is_none")]
311    pub requires_lto: Option<bool>,
312    #[serde(skip_serializing_if = "Option::is_none")]
313    pub requires_uwtable: Option<bool>,
314    #[serde(skip_serializing_if = "Option::is_none")]
315    pub rustc_abi: Option<String>,
316    #[serde(skip_serializing_if = "Option::is_none")]
317    pub split_debuginfo: Option<String>,
318    #[serde(skip_serializing_if = "Option::is_none")]
319    pub stack_probes: Option<StackProbes>,
320    #[serde(skip_serializing_if = "Option::is_none")]
321    pub static_initializer_must_be_acyclic: Option<bool>,
322    #[serde(skip_serializing_if = "Option::is_none")]
323    pub static_position_independent_executables: Option<bool>,
324    #[serde(skip_serializing_if = "Option::is_none")]
325    pub staticlib_prefix: Option<String>,
326    #[serde(skip_serializing_if = "Option::is_none")]
327    pub staticlib_suffix: Option<String>,
328    #[serde(default, skip_serializing_if = "Vec::is_empty")]
329    pub supported_sanitizers: Vec<Sanitizer>,
330    #[serde(default, skip_serializing_if = "Vec::is_empty")]
331    pub supported_split_debuginfo: Vec<String>,
332    #[serde(default = "default_true", skip_serializing_if = "Clone::clone")]
333    pub supports_stack_protector: bool,
334    #[serde(default, skip_serializing_if = "ops::Not::not")]
335    pub supports_fentry: bool,
336    #[serde(default, skip_serializing_if = "ops::Not::not")]
337    pub supports_xray: bool,
338    #[serde(skip_serializing_if = "Option::is_none")]
339    pub simd_types_indirect: Option<bool>,
340    #[serde(default, skip_serializing_if = "ops::Not::not")]
341    pub singlethread: bool,
342    #[serde(default, skip_serializing_if = "TargetEndian::is_little")]
343    pub target_endian: TargetEndian,
344    #[serde(default, skip_serializing_if = "Vec::is_empty")]
345    pub target_family: Vec<TargetFamily>,
346    #[serde(skip_serializing_if = "Option::is_none")]
347    pub target_mcount: Option<String>,
348    // Integer since 1.89
349    #[serde(skip_serializing_if = "Option::is_none")]
350    pub target_c_int_width: Option<u32>,
351    // Integer since 1.91
352    pub target_pointer_width: u32,
353    #[serde(skip_serializing_if = "Option::is_none")]
354    pub tls_model: Option<String>,
355    #[serde(skip_serializing_if = "Option::is_none")]
356    pub trap_unreachable: Option<bool>,
357    #[serde(default, skip_serializing_if = "Vec::is_empty")]
358    pub unsupported_cpus: Vec<String>,
359    #[serde(skip_serializing_if = "Option::is_none")]
360    pub use_ctors_section: Option<bool>,
361    #[serde(skip_serializing_if = "Option::is_none")]
362    pub vendor: Option<String>,
363}
364
365#[derive(Debug, Clone, Serialize, Deserialize)]
366#[cfg_attr(test, serde(deny_unknown_fields))]
367#[non_exhaustive]
368pub struct Metadata {
369    pub description: Option<String>,
370    pub host_tools: Option<bool>,
371    pub std: Option<bool>,
372    pub tier: Option<u32>,
373}
374
375#[derive(Debug, Clone, Serialize, Deserialize)]
376#[serde(rename_all = "kebab-case")]
377#[cfg_attr(test, serde(deny_unknown_fields))]
378#[non_exhaustive]
379pub struct StackProbes {
380    pub kind: String,
381    #[serde(skip_serializing_if = "Option::is_none")]
382    pub min_llvm_version_for_inline: Option<(u32, u32, u32)>,
383}
384
385fn default_true() -> bool {
386    true
387}
388
389/// `<rustc> -Z unstable-options --print target-spec-json --target <target>`
390pub fn target_spec_json(rustc: Command, target: &str) -> Result<TargetSpec> {
391    let raw = ProcessBuilder::from_std(rustc)
392        .args(["-Z", "unstable-options", "--print", "target-spec-json", "--target", target])
393        .read()?;
394    serde_json::from_str(&raw).map_err(Error::new)
395}
396
397/// `<rustc> -Z unstable-options --print all-target-specs-json`
398pub fn all_target_specs_json(rustc: Command) -> Result<AllTargetSpecs> {
399    let raw = ProcessBuilder::from_std(rustc)
400        .args(["-Z", "unstable-options", "--print", "all-target-specs-json"])
401        .read()?;
402    serde_json::from_str(&raw).map_err(Error::new)
403}
404
405#[cfg(test)]
406mod tests {
407    use std::eprintln;
408
409    use super::*;
410
411    fn target_spec_json(target: &str) -> Result<(TargetSpec, String)> {
412        let mut cmd = cmd!(
413            "rustc",
414            "-Z",
415            "unstable-options",
416            "--print",
417            "target-spec-json",
418            "--target",
419            target
420        );
421        if !rustversion::cfg!(nightly) {
422            cmd.env("RUSTC_BOOTSTRAP", "1");
423        }
424        let raw = cmd.read()?;
425        Ok((serde_json::from_str(&raw).map_err(Error::new)?, raw))
426    }
427
428    fn all_target_specs_json() -> Result<(AllTargetSpecs, String)> {
429        let mut cmd = cmd!("rustc", "-Z", "unstable-options", "--print", "all-target-specs-json");
430        if !rustversion::cfg!(nightly) {
431            cmd.env("RUSTC_BOOTSTRAP", "1");
432        }
433        let raw = cmd.read()?;
434        Ok((serde_json::from_str(&raw).map_err(Error::new)?, raw))
435    }
436
437    // Skip pre-1.91 because target-pointer-width change
438    #[rustversion::attr(before(1.91), ignore)]
439    #[test]
440    #[cfg_attr(miri, ignore)] // Miri doesn't support std::process::Command: https://github.com/rust-lang/miri/issues/3374
441    fn parse_target_spec_json() {
442        // builtin targets
443        for target in cmd!("rustc", "--print", "target-list").read().unwrap().lines() {
444            eprintln!("target={target}:");
445            let (parsed, raw) = target_spec_json(target).unwrap();
446            let deserialized = serde_json::to_string(&parsed).unwrap();
447            assert_eq!(
448                serde_json::from_str::<serde_json::Value>(&raw).unwrap(),
449                serde_json::from_str::<serde_json::Value>(&deserialized).unwrap()
450            );
451        }
452        eprintln!("all-targets:");
453        let (parsed, raw) = all_target_specs_json().unwrap();
454        let deserialized = serde_json::to_string(&parsed).unwrap();
455        assert_eq!(
456            serde_json::from_str::<serde_json::Value>(&raw).unwrap(),
457            serde_json::from_str::<serde_json::Value>(&deserialized).unwrap()
458        );
459        // TODO: custom targets
460        // for spec_path in fs::read_dir(fixtures_path().join("target-specs"))
461        //     .unwrap()
462        //     .map(|e| e.unwrap().path())
463        // {
464        // }
465    }
466}
target_spec_json/lib.rs

target_spec_json/
lib.rs
