1 files changed, 54 insertions, 0 deletions
diff --git a/third_party/rust/serde_json/build.rs b/third_party/rust/serde_json/build.rs
new file mode 100644
index 0000000000..0e12602e46
--- /dev/null
+++ b/third_party/rust/serde_json/build.rs
@@ -0,0 +1,54 @@
+use std::env;
+use std::process::Command;
+use std::str::{self, FromStr};
+
+fn main() {
+    println!("cargo:rerun-if-changed=build.rs");
+
+    // Decide ideal limb width for arithmetic in the float parser. Refer to
+    // src/lexical/math.rs for where this has an effect.
+    let target_arch = env::var("CARGO_CFG_TARGET_ARCH").unwrap();
+    match target_arch.as_str() {
+        "aarch64" | "mips64" | "powerpc64" | "x86_64" => {
+            println!("cargo:rustc-cfg=limb_width_64");
+        }
+        _ => {
+            println!("cargo:rustc-cfg=limb_width_32");
+        }
+    }
+
+    let minor = match rustc_minor_version() {
+        Some(minor) => minor,
+        None => return,
+    };
+
+    // BTreeMap::get_key_value
+    // https://blog.rust-lang.org/2019/12/19/Rust-1.40.0.html#additions-to-the-standard-library
+    if minor < 40 {
+        println!("cargo:rustc-cfg=no_btreemap_get_key_value");
+    }
+
+    // BTreeMap::remove_entry
+    // https://blog.rust-lang.org/2020/07/16/Rust-1.45.0.html#library-changes
+    if minor < 45 {
+        println!("cargo:rustc-cfg=no_btreemap_remove_entry");
+    }
+
+    // BTreeMap::retain
+    // https://blog.rust-lang.org/2021/06/17/Rust-1.53.0.html#stabilized-apis
+    if minor < 53 {
+        println!("cargo:rustc-cfg=no_btreemap_retain");
+    }
+}
+
+fn rustc_minor_version() -> Option<u32> {
+    let rustc = env::var_os("RUSTC")?;
+    let output = Command::new(rustc).arg("--version").output().ok()?;
+    let version = str::from_utf8(&output.stdout).ok()?;
+    let mut pieces = version.split('.');
+    if pieces.next() != Some("rustc 1") {
+        return None;
+    }
+    let next = pieces.next()?;
+    u32::from_str(next).ok()
+}