From 6032a677095a8b28e0a0778f996510c8abea3200 Mon Sep 17 00:00:00 2001
From: Jiahao XU <Jiahao_XU@outlook.com>
Date: Fri, 21 Jul 2023 13:45:16 +1000
Subject: [PATCH] Optimize `Build::get_out_dir`: Return `Cow<'_, Path>`

to avoid heap allocation if possible.

Signed-off-by: Jiahao XU <Jiahao_XU@outlook.com>
---
 src/lib.rs | 19 +++++++++++--------
 1 file changed, 11 insertions(+), 8 deletions(-)

diff --git a/src/lib.rs b/src/lib.rs
index 0f7fccaa..1d104f29 100644
--- a/src/lib.rs
+++ b/src/lib.rs
@@ -3121,15 +3121,18 @@ impl Build {
         self.force_frame_pointer.unwrap_or_else(|| self.get_debug())
     }
 
-    fn get_out_dir(&self) -> Result<PathBuf, Error> {
+    fn get_out_dir(&self) -> Result<Cow<'_, Path>, Error> {
         match &self.out_dir {
-            Some(p) => Ok((**p).into()),
-            None => Ok(env::var_os("OUT_DIR").map(PathBuf::from).ok_or_else(|| {
-                Error::new(
-                    ErrorKind::EnvVarNotFound,
-                    "Environment variable OUT_DIR not defined.",
-                )
-            })?),
+            Some(p) => Ok(Cow::Borrowed(&**p)),
+            None => env::var_os("OUT_DIR")
+                .map(PathBuf::from)
+                .map(Cow::Owned)
+                .ok_or_else(|| {
+                    Error::new(
+                        ErrorKind::EnvVarNotFound,
+                        "Environment variable OUT_DIR not defined.",
+                    )
+                }),
         }
     }