Implement Make `handle_alloc_error` default to panic (for no_std + liballoc)

Related: https://github.com/rust-lang/rust/issues/66741

Guarded with `#![feature(default_alloc_error_handler)]` a default
`alloc_error_handler` is called, if a custom allocator is used and no
other custom `#[alloc_error_handler]` is defined.

The panic message does not contain the size anymore, because it would
pull in the fmt machinery, which would blow up the code size
significantly.

2 files changed, 4 insertions, 2 deletions

diff --git a/compiler/rustc_codegen_ssa/src/base.rs b/compiler/rustc_codegen_ssa/src/base.rs
index d82fc2c9f63..8e6f8e193c0 100644
--- a/compiler/rustc_codegen_ssa/src/base.rs
+++ b/compiler/rustc_codegen_ssa/src/base.rs
@@ -538,8 +538,9 @@ pub fn codegen_crate<B: ExtraBackendMethods>(
         let llmod_id =
             cgu_name_builder.build_cgu_name(LOCAL_CRATE, &["crate"], Some("allocator")).to_string();
         let mut modules = backend.new_metadata(tcx, &llmod_id);
-        tcx.sess
-            .time("write_allocator_module", || backend.codegen_allocator(tcx, &mut modules, kind));
+        tcx.sess.time("write_allocator_module", || {
+            backend.codegen_allocator(tcx, &mut modules, kind, tcx.lang_items().oom().is_some())
+        });
 
         Some(ModuleCodegen { name: llmod_id, module_llvm: modules, kind: ModuleKind::Allocator })
     } else {
diff --git a/compiler/rustc_codegen_ssa/src/traits/backend.rs b/compiler/rustc_codegen_ssa/src/traits/backend.rs
index 90520f77e3c..48c07b00894 100644
--- a/compiler/rustc_codegen_ssa/src/traits/backend.rs
+++ b/compiler/rustc_codegen_ssa/src/traits/backend.rs
@@ -109,6 +109,7 @@ pub trait ExtraBackendMethods: CodegenBackend + WriteBackendMethods + Sized + Se
         tcx: TyCtxt<'tcx>,
         mods: &mut Self::Module,
         kind: AllocatorKind,
+        has_alloc_error_handler: bool,
     );
     /// This generates the codegen unit and returns it along with
     /// a `u64` giving an estimate of the unit's processing cost.