From fb29a312143d2a271f7243c834f5b34281af523d Mon Sep 17 00:00:00 2001
From: Daniel Verkamp <dverkamp@chromium.org>
Date: Mon, 22 Apr 2019 15:55:09 -0700
Subject: [PATCH] Allow overriding system root via environment

Use the PKG_CONFIG_SYSROOT_DIR (preferred) or SYSROOT (fallback)
environment variables to override the default path used to determine
whether a library is a system library or not (/usr).

This enables cross-compilation scenarios where the system root is not a
subdirectory of /usr. Specifically, when building Rust packages in the
Chomium OS SDK, each board's sysroot is located in /build/$BOARD rather
than a subdirectory of /usr. Additionally, cros_sdk only specifies
SYSROOT (PKG_CONFIG_SYSROOT_DIR is set by the pkg-config-$BOARD cross
compilation helpers, but that isn't available in pkg-config-rs).

This has only been tested on Linux, as I don't have a macOS machine
handy, but I believe the macOS path should work as before (it does not
consider the new sysroot variables).

Signed-off-by: Daniel Verkamp <dverkamp@chromium.org>
---
 src/lib.rs | 34 ++++++++++++++++++++--------------
 1 file changed, 20 insertions(+), 14 deletions(-)

diff --git a/src/lib.rs b/src/lib.rs
index d85dd98..bd7f800 100644
--- a/src/lib.rs
+++ b/src/lib.rs
@@ -71,7 +71,7 @@ use std::error;
 use std::ffi::{OsStr, OsString};
 use std::fmt;
 use std::io;
-use std::path::{PathBuf, Path};
+use std::path::PathBuf;
 use std::process::{Command, Output};
 use std::str;
 
@@ -470,6 +470,16 @@ impl Library {
     }
 
     fn parse_libs_cflags(&mut self, name: &str, output: &[u8], config: &Config) {
+        let system_roots = if cfg!(target_os = "macos") {
+            vec![PathBuf::from("/Library"), PathBuf::from("/System")]
+        } else {
+            let sysroot = config
+                .env_var("PKG_CONFIG_SYSROOT_DIR")
+                .or_else(|_| config.env_var("SYSROOT"))
+                .unwrap_or_else(|_| "/usr".to_owned());
+            vec![PathBuf::from(&sysroot)]
+        };
+
         let words = split_flags(output);
         let parts = words.iter()
                           .filter(|l| l.len() > 2)
@@ -496,7 +506,7 @@ impl Library {
                 }
                 "-l" => {
                     self.libs.push(val.to_string());
-                    if statik && is_static_available(val, &dirs) {
+                    if statik && is_static_available(val, &system_roots, &dirs) {
                         let meta = format!("rustc-link-lib=static={}", val);
                         config.print_metadata(&meta);
                     } else {
@@ -542,13 +552,8 @@ fn envify(name: &str) -> String {
 }
 
 /// System libraries should only be linked dynamically
-fn is_static_available(name: &str, dirs: &[PathBuf]) -> bool {
+fn is_static_available(name: &str, system_roots: &[PathBuf], dirs: &[PathBuf]) -> bool {
     let libname = format!("lib{}.a", name);
-    let system_roots = if cfg!(target_os = "macos") {
-        vec![Path::new("/Library"), Path::new("/System")]
-    } else {
-        vec![Path::new("/usr")]
-    };
 
     dirs.iter().any(|dir| {
         !system_roots.iter().any(|sys| dir.starts_with(sys)) &&
@@ -616,19 +621,20 @@ fn split_flags(output: &[u8]) -> Vec<String> {
 #[test]
 #[cfg(target_os = "macos")]
 fn system_library_mac_test() {
-    assert!(!is_static_available("PluginManager", &[PathBuf::from("/Library/Frameworks")]));
-    assert!(!is_static_available("python2.7", &[PathBuf::from("/System/Library/Frameworks/Python.framework/Versions/2.7/lib/python2.7/config")]));
-    assert!(!is_static_available("ffi_convenience", &[PathBuf::from("/Library/Ruby/Gems/2.0.0/gems/ffi-1.9.10/ext/ffi_c/libffi-x86_64/.libs")]));
+    let system_roots = vec![PathBuf::from("/Library"), PathBuf::from("/System")];
+    assert!(!is_static_available("PluginManager", &system_roots, &[PathBuf::from("/Library/Frameworks")]));
+    assert!(!is_static_available("python2.7", &system_roots, &[PathBuf::from("/System/Library/Frameworks/Python.framework/Versions/2.7/lib/python2.7/config")]));
+    assert!(!is_static_available("ffi_convenience", &system_roots, &[PathBuf::from("/Library/Ruby/Gems/2.0.0/gems/ffi-1.9.10/ext/ffi_c/libffi-x86_64/.libs")]));
 
     // Homebrew is in /usr/local, and it's not a part of the OS
     if Path::new("/usr/local/lib/libpng16.a").exists() {
-        assert!(is_static_available("png16", &[PathBuf::from("/usr/local/lib")]));
+        assert!(is_static_available("png16", &system_roots, &[PathBuf::from("/usr/local/lib")]));
     }
 }
 
 #[test]
 #[cfg(target_os = "linux")]
 fn system_library_linux_test() {
-    assert!(!is_static_available("util", &[PathBuf::from("/usr/lib/x86_64-linux-gnu")]));
-    assert!(!is_static_available("dialog", &[PathBuf::from("/usr/lib")]));
+    assert!(!is_static_available("util", &[PathBuf::from("/usr")], &[PathBuf::from("/usr/lib/x86_64-linux-gnu")]));
+    assert!(!is_static_available("dialog", &[PathBuf::from("/usr")], &[PathBuf::from("/usr/lib")]));
 }
-- 
2.21.0.593.g511ec345e18-goog