From 90e286da0716dc928f1cc2526fbe76438bb6f635 Mon Sep 17 00:00:00 2001
From: Eric Huss <eric@huss.org>
Date: Mon, 5 Oct 2020 08:15:32 -0700
Subject: [PATCH] Fix dylib+rlib with LTO.

---
 src/cargo/core/compiler/lto.rs | 12 ++++++------
 tests/testsuite/lto.rs         | 32 ++++++++++++++++++++++++++++++++
 2 files changed, 38 insertions(+), 6 deletions(-)

diff --git a/src/cargo/core/compiler/lto.rs b/src/cargo/core/compiler/lto.rs
index 5c401e82a1d..222578918e9 100644
--- a/src/cargo/core/compiler/lto.rs
+++ b/src/cargo/core/compiler/lto.rs
@@ -73,16 +73,16 @@ fn needs_object(crate_types: &[CrateType]) -> bool {
 
 /// Lto setting to use when this unit needs object code.
 fn lto_when_needs_object(crate_types: &[CrateType]) -> Lto {
-    if crate_types.iter().any(CrateType::can_lto) {
-        // A mixed rlib/cdylib whose parent is running LTO. This
-        // needs both, for bitcode in the rlib (for LTO) and the
-        // cdylib requires object code.
-        Lto::ObjectAndBitcode
-    } else {
+    if crate_types.iter().all(|ct| *ct == CrateType::Dylib) {
         // A dylib whose parent is running LTO. rustc currently
         // doesn't support LTO with dylibs, so bitcode is not
         // needed.
         Lto::OnlyObject
+    } else {
+        // Mixed rlib with a dylib or cdylib whose parent is running LTO. This
+        // needs both: bitcode for the rlib (for LTO) and object code for the
+        // dylib.
+        Lto::ObjectAndBitcode
     }
 }
 
diff --git a/tests/testsuite/lto.rs b/tests/testsuite/lto.rs
index cd69ce42809..9e2f9a42835 100644
--- a/tests/testsuite/lto.rs
+++ b/tests/testsuite/lto.rs
@@ -746,3 +746,35 @@ fn doctest() {
         .with_stderr_contains("[..]`rustdoc [..]-C lto[..]")
         .run();
 }
+
+#[cargo_test]
+fn dylib_rlib_bin() {
+    // dylib+rlib linked with a binary
+    let p = project()
+        .file(
+            "Cargo.toml",
+            r#"
+                [package]
+                name = "foo"
+                version = "0.1.0"
+
+                [lib]
+                crate-type = ["dylib", "rlib"]
+
+                [profile.release]
+                lto = true
+            "#,
+        )
+        .file("src/lib.rs", "pub fn foo() { println!(\"hi!\"); }")
+        .file("src/main.rs", "fn main() { foo::foo(); }")
+        .build();
+
+    let output = p.cargo("build --release -v").exec_with_output().unwrap();
+    verify_lto(
+        &output,
+        "foo",
+        "--crate-type dylib --crate-type rlib",
+        Lto::ObjectAndBitcode,
+    );
+    verify_lto(&output, "foo", "--crate-type bin", Lto::Run(None));
+}