Stop exporting rust_eh_personality and friends from cdylib

Author: nbdd0121

compiler/rustc_codegen_ssa/src/back/symbol_export.rs

@@ -105,24 +105,18 @@ fn reachable_non_generics_provider(tcx: TyCtxt<'_>, cnum: CrateNum) -> DefIdMap<
             }
         })
         .map(|def_id| {
-            let export_level = if special_runtime_crate {
+            let (export_level, used) = if special_runtime_crate {
                 let name = tcx.symbol_name(Instance::mono(tcx, def_id.to_def_id())).name;
-                // We can probably do better here by just ensuring that
-                // it has hidden visibility rather than public
-                // visibility, as this is primarily here to ensure it's
-                // not stripped during LTO.
-                //
-                // In general though we won't link right if these
-                // symbols are stripped, and LTO currently strips them.
-                match name {
+                // We won't link right if these symbols are stripped during LTO.
+                let used = match name {
                     "rust_eh_personality"
                     | "rust_eh_register_frames"
-                    | "rust_eh_unregister_frames" =>
-                        SymbolExportLevel::C,
-                    _ => SymbolExportLevel::Rust,
-                }
+                    | "rust_eh_unregister_frames" => true,
+                    _ => false,
+                };
+                (SymbolExportLevel::Rust, used)
             } else {
-                symbol_export_level(tcx, def_id.to_def_id())
+                (symbol_export_level(tcx, def_id.to_def_id()), false)
             };
             let codegen_attrs = tcx.codegen_fn_attrs(def_id.to_def_id());
             debug!(
@@ -142,7 +136,7 @@ fn reachable_non_generics_provider(tcx: TyCtxt<'_>, cnum: CrateNum) -> DefIdMap<
                     SymbolExportKind::Text
                 },
                 used: codegen_attrs.flags.contains(CodegenFnAttrFlags::USED)
-                    || codegen_attrs.flags.contains(CodegenFnAttrFlags::USED_LINKER),
+                    || codegen_attrs.flags.contains(CodegenFnAttrFlags::USED_LINKER) || used,
             })
         })
         .collect();