Implement JsonSchema for atomics

schemars/build.rs

@@ -0,0 +1,67 @@
+use std::env;
+use std::process::Command;
+use std::str::{self, FromStr};
+
+// Based on https://github.com/serde-rs/serde/blob/master/serde/build.rs
+
+fn main() {
+    let minor = match rustc_minor_version() {
+        Some(minor) => minor,
+        None => return,
+    };
+
+    let target = env::var("TARGET").unwrap();
+    let emscripten = target == "asmjs-unknown-emscripten" || target == "wasm32-unknown-emscripten";
+
+    // Atomic types, and non-zero signed integers stabilized in Rust 1.34:
+    // https://blog.rust-lang.org/2019/04/11/Rust-1.34.0.html#library-stabilizations
+    if minor >= 34 {
+        println!("cargo:rustc-cfg=num_nonzero_signed");
+
+        // Whitelist of archs that support std::sync::atomic module. Ideally we
+        // would use #[cfg(target_has_atomic = "...")] but it is not stable yet.
+        // Instead this is based on rustc's src/librustc_target/spec/*.rs.
+        let has_atomic64 = target.starts_with("x86_64")
+            || target.starts_with("i686")
+            || target.starts_with("aarch64")
+            || target.starts_with("powerpc64")
+            || target.starts_with("sparc64")
+            || target.starts_with("mips64el");
+        let has_atomic32 = has_atomic64 || emscripten;
+        if has_atomic64 {
+            println!("cargo:rustc-cfg=std_atomic64");
+        }
+        if has_atomic32 {
+            println!("cargo:rustc-cfg=std_atomic");
+        }
+    }
+}
+
+fn rustc_minor_version() -> Option<u32> {
+    let rustc = match env::var_os("RUSTC") {
+        Some(rustc) => rustc,
+        None => return None,
+    };
+
+    let output = match Command::new(rustc).arg("--version").output() {
+        Ok(output) => output,
+        Err(_) => return None,
+    };
+
+    let version = match str::from_utf8(&output.stdout) {
+        Ok(version) => version,
+        Err(_) => return None,
+    };
+
+    let mut pieces = version.split('.');
+    if pieces.next() != Some("rustc 1") {
+        return None;
+    }
+
+    let next = match pieces.next() {
+        Some(next) => next,
+        None => return None,
+    };
+
+    u32::from_str(next).ok()
+}