From e6cd499e9894d24a4382e9838db33b3565a6afe8 Mon Sep 17 00:00:00 2001
From: Sergei Grebnov <sergei.grebnov@gmail.com>
Date: Wed, 22 Jan 2025 13:19:48 -0800
Subject: [PATCH] Fix candle-flash-attn build on Windows (msvc) (#2734)

---
 candle-flash-attn/build.rs | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/candle-flash-attn/build.rs b/candle-flash-attn/build.rs
index 37247646e..18694524f 100644
--- a/candle-flash-attn/build.rs
+++ b/candle-flash-attn/build.rs
@@ -88,6 +88,12 @@ fn main() -> Result<()> {
         .arg("--use_fast_math")
         .arg("--verbose");
 
+    if let Ok(target) = std::env::var("TARGET") {
+        if target.contains("msvc") {
+            builder = builder.arg("-D_USE_MATH_DEFINES");
+        }
+    }
+
     let out_file = build_dir.join("libflashattention.a");
     builder.build_lib(out_file);