102 lines
3.5 KiB
Rust
102 lines
3.5 KiB
Rust
use autocfg::AutoCfg;
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const CONST_THREAD_LOCAL_PROBE: &str = r#"
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{
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thread_local! {
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static MY_PROBE: usize = const { 10 };
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}
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MY_PROBE.with(|val| *val)
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}
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"#;
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const ADDR_OF_PROBE: &str = r#"
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{
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let my_var = 10;
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::std::ptr::addr_of!(my_var)
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}
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"#;
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fn main() {
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let mut enable_const_thread_local = false;
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let mut enable_addr_of = false;
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match AutoCfg::new() {
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Ok(ac) => {
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// These checks prefer to call only `probe_rustc_version` if that is
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// enough to determine whether the feature is supported. This is
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// because the `probe_expression` call involves a call to rustc,
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// which the `probe_rustc_version` call avoids.
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// Const-initialized thread locals were stabilized in 1.59.
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if ac.probe_rustc_version(1, 60) {
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enable_const_thread_local = true;
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} else if ac.probe_rustc_version(1, 59) {
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// This compiler claims to be 1.59, but there are some nightly
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// compilers that claim to be 1.59 without supporting the
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// feature. Explicitly probe to check if code using them
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// compiles.
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//
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// The oldest nightly that supports the feature is 2021-12-06.
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if ac.probe_expression(CONST_THREAD_LOCAL_PROBE) {
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enable_const_thread_local = true;
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}
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}
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// The `addr_of` and `addr_of_mut` macros were stabilized in 1.51.
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if ac.probe_rustc_version(1, 52) {
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enable_addr_of = true;
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} else if ac.probe_rustc_version(1, 51) {
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// This compiler claims to be 1.51, but there are some nightly
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// compilers that claim to be 1.51 without supporting the
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// feature. Explicitly probe to check if code using them
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// compiles.
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//
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// The oldest nightly that supports the feature is 2021-01-31.
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if ac.probe_expression(ADDR_OF_PROBE) {
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enable_addr_of = true;
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}
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}
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}
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Err(e) => {
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// If we couldn't detect the compiler version and features, just
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// print a warning. This isn't a fatal error: we can still build
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// Tokio, we just can't enable cfgs automatically.
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println!(
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"cargo:warning=tokio: failed to detect compiler features: {}",
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e
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);
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}
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}
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if !enable_const_thread_local {
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// To disable this feature on compilers that support it, you can
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// explicitly pass this flag with the following environment variable:
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//
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// RUSTFLAGS="--cfg tokio_no_const_thread_local"
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autocfg::emit("tokio_no_const_thread_local")
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}
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if !enable_addr_of {
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// To disable this feature on compilers that support it, you can
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// explicitly pass this flag with the following environment variable:
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//
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// RUSTFLAGS="--cfg tokio_no_addr_of"
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autocfg::emit("tokio_no_addr_of")
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}
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let target = ::std::env::var("TARGET").unwrap_or_default();
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// We emit cfgs instead of using `target_family = "wasm"` that requires Rust 1.54.
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// Note that these cfgs are unavailable in `Cargo.toml`.
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if target.starts_with("wasm") {
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autocfg::emit("tokio_wasm");
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if target.contains("wasi") {
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autocfg::emit("tokio_wasi");
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} else {
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autocfg::emit("tokio_wasm_not_wasi");
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}
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}
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}
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