From 4f86c5058740a9295b74f87c8cab6206a60e9971 Mon Sep 17 00:00:00 2001
From: Lars Eggert <lars@eggert.org>
Date: Fri, 11 Oct 2024 13:14:57 +0300
Subject: [PATCH] Use `cfg` instead of `feature`

---
 quinn-udp/Cargo.toml | 2 --
 quinn-udp/build.rs   | 9 +++++++--
 2 files changed, 7 insertions(+), 4 deletions(-)

diff --git a/quinn-udp/Cargo.toml b/quinn-udp/Cargo.toml
index c4c0ada257..7e88790f1c 100644
--- a/quinn-udp/Cargo.toml
+++ b/quinn-udp/Cargo.toml
@@ -18,8 +18,6 @@ default = ["tracing", "log"]
 # Configure `tracing` to log events via `log` if no `tracing` subscriber exists.
 log = ["tracing/log"]
 direct-log = ["dep:log"]
-# Use private Apple APIs to send multiple packets in a single syscall.
-fast-apple-datapath = []
 
 [dependencies]
 libc = "0.2.158"
diff --git a/quinn-udp/build.rs b/quinn-udp/build.rs
index ef89ff70fb..f49aee8625 100644
--- a/quinn-udp/build.rs
+++ b/quinn-udp/build.rs
@@ -1,6 +1,11 @@
 use cfg_aliases::cfg_aliases;
 
 fn main() {
+    if std::env::var("CARGO_CFG_QUINN_UDP_APPLE_FAST_DATAPATH").is_ok() {
+        // Use private Apple APIs to send multiple packets in a single syscall.
+        println!("cargo:rustc-cfg=quinn_udp_apple_fast_datapath");
+    };
+
     // Setup cfg aliases
     cfg_aliases! {
         // Platforms
@@ -20,7 +25,7 @@ fn main() {
             )
         },
         // Convenience aliases
-        apple_fast: { all(apple, feature = "fast-apple-datapath") },
-        apple_slow: { all(apple, not(feature = "fast-apple-datapath")) },
+        apple_fast: { all(apple, quinn_udp_apple_fast_datapath) },
+        apple_slow: { all(apple, not(quinn_udp_apple_fast_datapath)) },
     }
 }