Format sources into the error message when loading codegen backends

Cargo.lock

@@ -2177,16 +2177,6 @@ dependencies = [
  "cc",
 ]
 
-[[package]]
-name = "libloading"
-version = "0.7.4"
-source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "b67380fd3b2fbe7527a606e18729d21c6f3951633d0500574c4dc22d2d638b9f"
-dependencies = [
- "cfg-if",
- "winapi",
-]
-
 [[package]]
 name = "libloading"
 version = "0.8.1"
@@ -2469,7 +2459,7 @@ dependencies = [
  "lazy_static",
  "libc",
  "libffi",
- "libloading 0.8.1",
+ "libloading",
  "log",
  "measureme",
  "rand",
@@ -3993,7 +3983,7 @@ dependencies = [
 name = "rustc_interface"
 version = "0.0.0"
 dependencies = [
- "libloading 0.7.4",
+ "libloading",
  "rustc-rayon",
  "rustc-rayon-core",
  "rustc_ast",
@@ -4123,7 +4113,7 @@ name = "rustc_metadata"
 version = "0.0.0"
 dependencies = [
  "bitflags 2.4.1",
- "libloading 0.7.4",
+ "libloading",
  "odht",
  "rustc_ast",
  "rustc_attr",

compiler/rustc_codegen_cranelift/Cargo.lock

@@ -246,12 +246,12 @@ checksum = "9cdc71e17332e86d2e1d38c1f99edcb6288ee11b815fb1a4b049eaa2114d369b"
 
 [[package]]
 name = "libloading"
-version = "0.7.4"
+version = "0.8.1"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "b67380fd3b2fbe7527a606e18729d21c6f3951633d0500574c4dc22d2d638b9f"
+checksum = "c571b676ddfc9a8c12f1f3d3085a7b163966a8fd8098a90640953ce5f6170161"
 dependencies = [
  "cfg-if",
- "winapi",
+ "windows-sys",
 ]
 
 [[package]]

compiler/rustc_codegen_cranelift/Cargo.toml

@@ -19,7 +19,7 @@ gimli = { version = "0.28", default-features = false, features = ["write"]}
 object = { version = "0.32", default-features = false, features = ["std", "read_core", "write", "archive", "coff", "elf", "macho", "pe"] }
 
 indexmap = "2.0.0"
-libloading = { version = "0.7.3", optional = true }
+libloading = { version = "0.8.0", optional = true }
 smallvec = "1.8.1"
 
 [patch.crates-io]

compiler/rustc_interface/Cargo.toml

@@ -5,7 +5,7 @@ edition = "2021"
 
 [dependencies]
 # tidy-alphabetical-start
-libloading = "0.7.1"
+libloading = "0.8.0"
 rustc-rayon = { version = "0.5.0", optional = true }
 rustc-rayon-core = { version = "0.5.0", optional = true }
 rustc_ast = { path = "../rustc_ast" }

compiler/rustc_interface/src/lib.rs

@@ -1,9 +1,10 @@
 #![feature(box_patterns)]
 #![feature(decl_macro)]
+#![feature(error_iter)]
 #![feature(internal_output_capture)]
-#![feature(thread_spawn_unchecked)]
 #![feature(lazy_cell)]
 #![feature(let_chains)]
+#![feature(thread_spawn_unchecked)]
 #![feature(try_blocks)]
 #![recursion_limit = "256"]
 #![deny(rustc::untranslatable_diagnostic)]

compiler/rustc_interface/src/util.rs

@@ -162,15 +162,21 @@ pub(crate) fn run_in_thread_pool_with_globals<F: FnOnce() -> R + Send, R: Send>(
 }
 
 fn load_backend_from_dylib(early_dcx: &EarlyDiagCtxt, path: &Path) -> MakeBackendFn {
+    fn format_err(e: &(dyn std::error::Error + 'static)) -> String {
+        e.sources().map(|e| format!(": {e}")).collect()
+    }
     let lib = unsafe { Library::new(path) }.unwrap_or_else(|err| {
-        let err = format!("couldn't load codegen backend {path:?}: {err}");
+        let err = format!("couldn't load codegen backend {path:?}{}", format_err(&err));
         early_dcx.early_fatal(err);
     });
 
     let backend_sym = unsafe { lib.get::<MakeBackendFn>(b"__rustc_codegen_backend") }
         .unwrap_or_else(|e| {
-            let err = format!("couldn't load codegen backend: {e}");
-            early_dcx.early_fatal(err);
+            let e = format!(
+                "`__rustc_codegen_backend` symbol lookup in the codegen backend failed{}",
+                format_err(&e)
+            );
+            early_dcx.early_fatal(e);
         });
 
     // Intentionally leak the dynamic library. We can't ever unload it

compiler/rustc_metadata/Cargo.toml

@@ -6,7 +6,7 @@ edition = "2021"
 [dependencies]
 # tidy-alphabetical-start
 bitflags = "2.4.1"
-libloading = "0.7.1"
+libloading = "0.8.0"
 odht = { version = "0.3.1", features = ["nightly"] }
 rustc_ast = { path = "../rustc_ast" }
 rustc_attr = { path = "../rustc_attr" }