From 4b6a0278fe2d1c8d74a6bfe5b14c3022ca3b3c46 Mon Sep 17 00:00:00 2001
From: Federico Ponzi <isaacisback92@gmail.com>
Date: Sat, 18 Jul 2020 00:01:27 +0200
Subject: [PATCH 1/2] fixes #67108 by using the external crate

---
 Cargo.lock                             |  7 ++++++
 src/librustc_codegen_ssa/Cargo.toml    |  1 +
 src/librustc_codegen_ssa/back/rpath.rs | 33 ++------------------------
 3 files changed, 10 insertions(+), 31 deletions(-)

diff --git a/Cargo.lock b/Cargo.lock
index 28ff6b3b1ebf2..3ee7d07900700 100644
--- a/Cargo.lock
+++ b/Cargo.lock
@@ -2142,6 +2142,12 @@ dependencies = [
  "winapi 0.3.8",
 ]
 
+[[package]]
+name = "pathdiff"
+version = "0.2.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "877630b3de15c0b64cc52f659345724fbf6bdad9bd9566699fc53688f3c34a34"
+
 [[package]]
 name = "percent-encoding"
 version = "1.0.1"
@@ -3318,6 +3324,7 @@ dependencies = [
  "log",
  "memmap",
  "num_cpus",
+ "pathdiff",
  "rustc_apfloat",
  "rustc_ast",
  "rustc_attr",
diff --git a/src/librustc_codegen_ssa/Cargo.toml b/src/librustc_codegen_ssa/Cargo.toml
index eeb6b4aabcf29..e100e0095c92a 100644
--- a/src/librustc_codegen_ssa/Cargo.toml
+++ b/src/librustc_codegen_ssa/Cargo.toml
@@ -18,6 +18,7 @@ log = "0.4.5"
 libc = "0.2.50"
 jobserver = "0.1.11"
 tempfile = "3.1"
+pathdiff = "0.2.0"
 
 rustc_serialize = { path = "../librustc_serialize" }
 rustc_ast = { path = "../librustc_ast" }
diff --git a/src/librustc_codegen_ssa/back/rpath.rs b/src/librustc_codegen_ssa/back/rpath.rs
index c02e4f279b1fb..e1d649c6ed3de 100644
--- a/src/librustc_codegen_ssa/back/rpath.rs
+++ b/src/librustc_codegen_ssa/back/rpath.rs
@@ -2,6 +2,7 @@ use rustc_data_structures::fx::FxHashSet;
 use std::env;
 use std::fs;
 use std::path::{Path, PathBuf};
+use pathdiff::diff_paths;
 
 use rustc_hir::def_id::CrateNum;
 use rustc_middle::middle::cstore::LibSource;
@@ -109,37 +110,7 @@ fn get_rpath_relative_to_output(config: &mut RPathConfig<'_>, lib: &Path) -> Str
 // In particular, this handles the case on unix where both paths are
 // absolute but with only the root as the common directory.
 fn path_relative_from(path: &Path, base: &Path) -> Option<PathBuf> {
-    use std::path::Component;
-
-    if path.is_absolute() != base.is_absolute() {
-        path.is_absolute().then(|| PathBuf::from(path))
-    } else {
-        let mut ita = path.components();
-        let mut itb = base.components();
-        let mut comps: Vec<Component<'_>> = vec![];
-        loop {
-            match (ita.next(), itb.next()) {
-                (None, None) => break,
-                (Some(a), None) => {
-                    comps.push(a);
-                    comps.extend(ita.by_ref());
-                    break;
-                }
-                (None, _) => comps.push(Component::ParentDir),
-                (Some(a), Some(b)) if comps.is_empty() && a == b => (),
-                (Some(a), Some(b)) if b == Component::CurDir => comps.push(a),
-                (Some(_), Some(b)) if b == Component::ParentDir => return None,
-                (Some(a), Some(_)) => {
-                    comps.push(Component::ParentDir);
-                    comps.extend(itb.map(|_| Component::ParentDir));
-                    comps.push(a);
-                    comps.extend(ita.by_ref());
-                    break;
-                }
-            }
-        }
-        Some(comps.iter().map(|c| c.as_os_str()).collect())
-    }
+    diff_paths(path, base)
 }
 
 fn get_install_prefix_rpath(config: &mut RPathConfig<'_>) -> String {

From 5702ce8962b37affa29d9acafeefdf379fdd1dcd Mon Sep 17 00:00:00 2001
From: Federico Ponzi <isaacisback92@gmail.com>
Date: Sat, 18 Jul 2020 01:00:17 +0200
Subject: [PATCH 2/2] Allows pathdiff package

---
 src/tools/tidy/src/deps.rs | 1 +
 1 file changed, 1 insertion(+)

diff --git a/src/tools/tidy/src/deps.rs b/src/tools/tidy/src/deps.rs
index b7d3d428cd283..559267a494f29 100644
--- a/src/tools/tidy/src/deps.rs
+++ b/src/tools/tidy/src/deps.rs
@@ -123,6 +123,7 @@ const PERMITTED_DEPENDENCIES: &[&str] = &[
     "opaque-debug",
     "parking_lot",
     "parking_lot_core",
+    "pathdiff",
     "pkg-config",
     "polonius-engine",
     "ppv-lite86",