Prevent insta-stable no alloc shim support

You will need to add the following as replacement for the old __rust_*
definitions when not using the alloc shim.

    #[no_mangle]
    static __rust_no_alloc_shim_is_unstable: u8 = 0;

1 files changed, 9 insertions, 1 deletions

diff --git a/compiler/rustc_codegen_llvm/src/allocator.rs b/compiler/rustc_codegen_llvm/src/allocator.rs
index 564e996cdf3..a57508815d6 100644
--- a/compiler/rustc_codegen_llvm/src/allocator.rs
+++ b/compiler/rustc_codegen_llvm/src/allocator.rs
@@ -2,7 +2,7 @@ use crate::attributes;
 use libc::c_uint;
 use rustc_ast::expand::allocator::{
     alloc_error_handler_name, default_fn_name, global_fn_name, AllocatorKind, AllocatorTy,
-    ALLOCATOR_METHODS,
+    ALLOCATOR_METHODS, NO_ALLOC_SHIM_IS_UNSTABLE,
 };
 use rustc_middle::bug;
 use rustc_middle::ty::TyCtxt;
@@ -161,6 +161,14 @@ pub(crate) unsafe fn codegen(
     let llval = llvm::LLVMConstInt(i8, val as u64, False);
     llvm::LLVMSetInitializer(ll_g, llval);
 
+    let name = NO_ALLOC_SHIM_IS_UNSTABLE;
+    let ll_g = llvm::LLVMRustGetOrInsertGlobal(llmod, name.as_ptr().cast(), name.len(), i8);
+    if tcx.sess.target.default_hidden_visibility {
+        llvm::LLVMRustSetVisibility(ll_g, llvm::Visibility::Hidden);
+    }
+    let llval = llvm::LLVMConstInt(i8, 0, False);
+    llvm::LLVMSetInitializer(ll_g, llval);
+
     if tcx.sess.opts.debuginfo != DebugInfo::None {
         let dbg_cx = debuginfo::CodegenUnitDebugContext::new(llmod);
         debuginfo::metadata::build_compile_unit_di_node(tcx, module_name, &dbg_cx);