From 307a31518fa44125d7d56d26048c904c5f5fda21 Mon Sep 17 00:00:00 2001
From: "L. E. Segovia" <amy@amyspark.me>
Date: Fri, 25 Aug 2023 22:04:23 -0300
Subject: [PATCH] Fix package detection and build when cross-compiling from
 MSVC to GNU

I and @dragonmux found two issues when building libusb from a MSVC host
to a MinGW target. When the build.rs script is built for the MSVC host,

- the vcpkg crate is used for detection (which correctly detects the
  MinGW target and reports an unsupported ABI)
- a MSVC flag is applied to the build (and thus breaking the build
  altogether)

This commit fixes both issues by changing vcpkg to a Windows-wide
dependency, and then if CARGO_CFG_TARGET_ENV is indeed MSVC, it is used
and the /source-charset:utf-8 flag is applied.
---
 libusb1-sys/Cargo.toml |  2 +-
 libusb1-sys/build.rs   | 35 +++++++++++++++++------------------
 2 files changed, 18 insertions(+), 19 deletions(-)

diff --git a/libusb1-sys/Cargo.toml b/libusb1-sys/Cargo.toml
index 519accf..2612e78 100644
--- a/libusb1-sys/Cargo.toml
+++ b/libusb1-sys/Cargo.toml
@@ -39,7 +39,7 @@ vendored = []
 [dependencies]
 libc = "0.2"
 
-[target.'cfg(target_env = "msvc")'.build-dependencies]
+[target.'cfg(target_os = "windows")'.build-dependencies]
 vcpkg = "0.2"
 
 [build-dependencies]
diff --git a/libusb1-sys/build.rs b/libusb1-sys/build.rs
index 0fcad31..e3b16d2 100644
--- a/libusb1-sys/build.rs
+++ b/libusb1-sys/build.rs
@@ -19,21 +19,6 @@ pub fn link_framework(name: &str) {
     println!("cargo:rustc-link-lib=framework={}", name);
 }
 
-#[cfg(target_env = "msvc")]
-fn find_libusb_pkg(_statik: bool) -> bool {
-    match vcpkg::Config::new().find_package("libusb") {
-        Ok(_) => true,
-        Err(e) => {
-            if pkg_config::probe_library("libusb-1.0").is_ok() {
-                true
-            } else {
-                println!("Can't find libusb pkg: {:?}", e);
-                false
-            }
-        }
-    }
-}
-
 fn get_macos_major_version() -> Option<usize> {
     if !cfg!(target_os = "macos") {
         return None;
@@ -49,8 +34,21 @@ fn get_macos_major_version() -> Option<usize> {
     Some(major)
 }
 
-#[cfg(not(target_env = "msvc"))]
 fn find_libusb_pkg(statik: bool) -> bool {
+    if std::env::var("CARGO_CFG_TARGET_ENV") == Ok("msvc".into()) {
+        #[cfg(target_os = "windows")]
+        return match vcpkg::Config::new().find_package("libusb") {
+            Ok(_) => true,
+            Err(e) => {
+                if pkg_config::probe_library("libusb-1.0").is_ok() {
+                    true
+                } else {
+                    println!("Can't find libusb pkg: {:?}", e);
+                    false
+                }
+            }
+        };
+    }
     // https://github.com/rust-lang/rust/issues/96943
     let needs_rustc_issue_96943_workaround: bool = get_macos_major_version()
         .map(|major| major >= 11)
@@ -175,8 +173,9 @@ fn make_source() {
     }
 
     if std::env::var("CARGO_CFG_TARGET_OS") == Ok("windows".into()) {
-        #[cfg(target_env = "msvc")]
-        base_config.flag("/source-charset:utf-8");
+        if std::env::var("CARGO_CFG_TARGET_ENV") == Ok("msvc".into()) {
+            base_config.flag("/source-charset:utf-8");
+        }
 
         base_config.warnings(false);
         base_config.define("OS_WINDOWS", Some("1"));