From 2c3e8b1c503b1996f108ec356c2c71d0b241f0a1 Mon Sep 17 00:00:00 2001
From: James Hilliard <james.hilliard1@gmail.com>
Date: Mon, 22 Mar 2021 07:38:03 -0600
Subject: [PATCH] Ensure we are cross compiling when any cross env variables
 are set.

---
 CHANGELOG.md |  1 +
 build.rs     | 62 +++++++++++++++++++++++++++++-----------------------
 2 files changed, 36 insertions(+), 27 deletions(-)

diff --git a/CHANGELOG.md b/CHANGELOG.md
index 980a75c4d28..5099c9a5c84 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -46,6 +46,7 @@ and this project adheres to [Semantic Versioning](http://semver.org/spec/v2.0.0.
 - Fix inability to use a named lifetime for `&PyTuple` of `*args` in `#[pyfunction]`. [#1440](https://github.com/PyO3/pyo3/pull/1440)
 - Fix inability to add `#[text_signature]` to some `#[pyproto]` methods. [#1483](https://github.com/PyO3/pyo3/pull/1483)
 - Fix use of Python argument for #[pymethods] inside macro expansions. [#1505](https://github.com/PyO3/pyo3/pull/1505)
+- Always use cross-compiling configuration if any of the environment variables are set. [#1514](https://github.com/PyO3/pyo3/pull/1514)
 
 ## [0.13.2] - 2021-02-12
 ### Packaging
diff --git a/build.rs b/build.rs
index 2222b1d4485..3c2195a38af 100644
--- a/build.rs
+++ b/build.rs
@@ -151,36 +151,44 @@ impl CrossCompileConfig {
 }
 
 fn cross_compiling() -> Result<Option<CrossCompileConfig>> {
-    let target = env::var("TARGET")?;
-    let host = env::var("HOST")?;
-    if target == host {
-        // Not cross-compiling
-        return Ok(None);
-    }
+    if env::var_os("PYO3_CROSS").is_none()
+        && env::var_os("PYO3_CROSS_LIB_DIR").is_none()
+        && env::var_os("PYO3_CROSS_INCLUDE_DIR").is_none()
+        && env::var_os("PYO3_CROSS_VERSION").is_none()
+        && env::var_os("PYO3_CROSS_PYTHON_VERSION").is_none()
+    {
+        let target = env::var("TARGET")?;
+        let host = env::var("HOST")?;
+        if target == host {
+            // Not cross-compiling
+            return Ok(None);
+        }
 
-    if target == "i686-pc-windows-msvc" && host == "x86_64-pc-windows-msvc" {
-        // Not cross-compiling to compile for 32-bit Python from windows 64-bit
-        return Ok(None);
-    }
+        if target == "i686-pc-windows-msvc" && host == "x86_64-pc-windows-msvc" {
+            // Not cross-compiling to compile for 32-bit Python from windows 64-bit
+            return Ok(None);
+        }
 
-    if target == "x86_64-apple-darwin" && host == "aarch64-apple-darwin" {
-        // Not cross-compiling to compile for x86-64 Python from macOS arm64
-        return Ok(None);
-    }
-    if target == "aarch64-apple-darwin" && host == "x86_64-apple-darwin" {
-        // Not cross-compiling to compile for arm64 Python from macOS x86_64
-        return Ok(None);
-    }
+        if target == "x86_64-apple-darwin" && host == "aarch64-apple-darwin" {
+            // Not cross-compiling to compile for x86-64 Python from macOS arm64
+            return Ok(None);
+        }
 
-    if host.starts_with(&format!(
-        "{}-{}-{}",
-        env::var("CARGO_CFG_TARGET_ARCH")?,
-        env::var("CARGO_CFG_TARGET_VENDOR")?,
-        env::var("CARGO_CFG_TARGET_OS")?
-    )) {
-        // Not cross-compiling if arch-vendor-os is all the same
-        // e.g. x86_64-unknown-linux-musl on x86_64-unknown-linux-gnu host
-        return Ok(None);
+        if target == "aarch64-apple-darwin" && host == "x86_64-apple-darwin" {
+            // Not cross-compiling to compile for arm64 Python from macOS x86_64
+            return Ok(None);
+        }
+
+        if host.starts_with(&format!(
+            "{}-{}-{}",
+            env::var("CARGO_CFG_TARGET_ARCH")?,
+            env::var("CARGO_CFG_TARGET_VENDOR")?,
+            env::var("CARGO_CFG_TARGET_OS")?
+        )) {
+            // Not cross-compiling if arch-vendor-os is all the same
+            // e.g. x86_64-unknown-linux-musl on x86_64-unknown-linux-gnu host
+            return Ok(None);
+        }
     }
 
     if env::var("CARGO_CFG_TARGET_FAMILY")? == "windows" {