Revert "Remove #[alloc_error_handler] from the compiler and library"

This reverts commit abc0660118.

compiler/rustc_codegen_ssa/src/back/symbol_export.rs

@@ -219,7 +219,7 @@ fn exported_symbols_provider_local(
         for symbol_name in ALLOCATOR_METHODS
             .iter()
             .map(|method| format!("__rust_{}", method.name))
-            .chain([OomStrategy::SYMBOL.to_string()])
+            .chain(["__rust_alloc_error_handler".to_string(), OomStrategy::SYMBOL.to_string()])
         {
             let exported_symbol = ExportedSymbol::NoDefId(SymbolName::new(tcx, &symbol_name));
 

compiler/rustc_codegen_ssa/src/base.rs

@@ -635,9 +635,16 @@ pub fn codegen_crate<B: ExtraBackendMethods>(
     if let Some(kind) = allocator_kind_for_codegen(tcx) {
         let llmod_id =
             cgu_name_builder.build_cgu_name(LOCAL_CRATE, &["crate"], Some("allocator")).to_string();
-        let module_llvm = tcx
-            .sess
-            .time("write_allocator_module", || backend.codegen_allocator(tcx, &llmod_id, kind));
+        let module_llvm = tcx.sess.time("write_allocator_module", || {
+            backend.codegen_allocator(
+                tcx,
+                &llmod_id,
+                kind,
+                // If allocator_kind is Some then alloc_error_handler_kind must
+                // also be Some.
+                tcx.alloc_error_handler_kind(()).unwrap(),
+            )
+        });
 
         ongoing_codegen.submit_pre_codegened_module_to_llvm(
             tcx,

compiler/rustc_codegen_ssa/src/traits/backend.rs

@@ -123,6 +123,7 @@ pub trait ExtraBackendMethods: CodegenBackend + WriteBackendMethods + Sized + Se
         tcx: TyCtxt<'tcx>,
         module_name: &str,
         kind: AllocatorKind,
+        alloc_error_handler_kind: AllocatorKind,
     ) -> Self::Module;
     /// This generates the codegen unit and returns it along with
     /// a `u64` giving an estimate of the unit's processing cost.