From 4b441cea9ff585a444864ce3d61d689976af69a3 Mon Sep 17 00:00:00 2001
From: Thomas Vermeilh <ory@oryctero.pe>
Date: Wed, 14 Apr 2021 15:17:02 +0200
Subject: [PATCH] Add env var EXTRA_CLANG_ARGS_<TARGET>

Closes #2009
---
 README.md  |  4 ++++
 build.rs   |  8 ++++++++
 src/lib.rs | 13 +++++++++++--
 3 files changed, 23 insertions(+), 2 deletions(-)

diff --git a/README.md b/README.md
index e1ad557e9..60e064ffb 100644
--- a/README.md
+++ b/README.md
@@ -60,6 +60,10 @@ End-users should set these environment variables to modify `bindgen`'s behavior
     - Examples:
         - Specify alternate sysroot: `--sysroot=/path/to/sysroot`
         - Add include search path with spaces: `-I"/path/with spaces"`
+- `BINDGEN_EXTRA_CLANG_ARGS_<TARGET>`: similar to `BINDGEN_EXTRA_CLANG_ARGS`,
+   but used to set per-target arguments to pass to clang. Useful to set system include
+   directories in a target-specific way in cross-compilation environments with multiple targets.
+   Has precedence over `BINDGEN_EXTRA_CLANG_ARGS`.
 
 Additionally, `bindgen` uses `libclang` to parse C and C++ header files.
 To modify how `bindgen` searches for `libclang`, see the [`clang-sys` documentation][clang-sys-env].
diff --git a/build.rs b/build.rs
index cb40cb0c1..fcc0bb221 100644
--- a/build.rs
+++ b/build.rs
@@ -79,4 +79,12 @@ fn main() {
     println!("cargo:rerun-if-env-changed=LIBCLANG_PATH");
     println!("cargo:rerun-if-env-changed=LIBCLANG_STATIC_PATH");
     println!("cargo:rerun-if-env-changed=BINDGEN_EXTRA_CLANG_ARGS");
+    println!(
+        "cargo:rerun-if-env-changed=BINDGEN_EXTRA_CLANG_ARGS_{}",
+        std::env::var("TARGET").unwrap()
+    );
+    println!(
+        "cargo:rerun-if-env-changed=BINDGEN_EXTRA_CLANG_ARGS_{}",
+        std::env::var("TARGET").unwrap().replace("-", "_")
+    );
 }
diff --git a/src/lib.rs b/src/lib.rs
index 85d555992..385a0b2be 100644
--- a/src/lib.rs
+++ b/src/lib.rs
@@ -1404,8 +1404,17 @@ impl Builder {
     /// Generate the Rust bindings using the options built up thus far.
     pub fn generate(mut self) -> Result<Bindings, ()> {
         // Add any extra arguments from the environment to the clang command line.
-        if let Some(extra_clang_args) =
-            env::var("BINDGEN_EXTRA_CLANG_ARGS").ok()
+        if let Ok(extra_clang_args) = env::var("TARGET")
+            .and_then(|target| {
+                env::var(&format!("BINDGEN_EXTRA_CLANG_ARGS_{}", target))
+                    .or_else(|_| {
+                        env::var(&format!(
+                            "BINDGEN_EXTRA_CLANG_ARGS_{}",
+                            target.replace("-", "_")
+                        ))
+                    })
+            })
+            .or_else(|_| env::var("BINDGEN_EXTRA_CLANG_ARGS"))
         {
             // Try to parse it with shell quoting. If we fail, make it one single big argument.
             if let Some(strings) = shlex::split(&extra_clang_args) {