miri: make sure we can find link_section statics even for the local crate

compiler/rustc_passes/src/reachable.rs

@@ -30,7 +30,7 @@ use rustc_hir::def_id::{DefId, LocalDefId};
 use rustc_hir::intravisit::{self, Visitor};
 use rustc_hir::Node;
 use rustc_middle::bug;
-use rustc_middle::middle::codegen_fn_attrs::{CodegenFnAttrFlags, CodegenFnAttrs};
+use rustc_middle::middle::codegen_fn_attrs::CodegenFnAttrFlags;
 use rustc_middle::middle::privacy::{self, Level};
 use rustc_middle::mir::interpret::{ConstAllocation, ErrorHandled, GlobalAlloc};
 use rustc_middle::query::Providers;
@@ -178,15 +178,7 @@ impl<'tcx> ReachableContext<'tcx> {
         if !self.any_library {
             // If we are building an executable, only explicitly extern
             // types need to be exported.
-            let codegen_attrs = if self.tcx.def_kind(search_item).has_codegen_attrs() {
-                self.tcx.codegen_fn_attrs(search_item)
-            } else {
-                CodegenFnAttrs::EMPTY
-            };
-            let is_extern = codegen_attrs.contains_extern_indicator();
-            let std_internal =
-                codegen_attrs.flags.contains(CodegenFnAttrFlags::RUSTC_STD_INTERNAL_SYMBOL);
-            if is_extern || std_internal {
+            if has_custom_linkage(self.tcx, search_item) {
                 self.reachable_symbols.insert(search_item);
             }
         } else {

src/tools/miri/tests/pass/tls/win_tls_callback.rs

@@ -0,0 +1,16 @@
+//! Ensure that we call Windows TLS callbacks in the local crate.
+//@only-target-windows
+// Calling eprintln in the callback seems to (re-)initialize some thread-local storage
+// and then leak the memory allocated for that. Let's just ignore these leaks,
+// that's not what this test is about.
+//@compile-flags: -Zmiri-ignore-leaks
+
+#[link_section = ".CRT$XLB"]
+#[used] // Miri only considers explicitly `#[used]` statics for `lookup_link_section`
+pub static CALLBACK: unsafe extern "system" fn(*const (), u32, *const ()) = tls_callback;
+
+unsafe extern "system" fn tls_callback(_h: *const (), _dw_reason: u32, _pv: *const ()) {
+    eprintln!("in tls_callback");
+}
+
+fn main() {}

src/tools/miri/tests/pass/tls/win_tls_callback.stderr

@@ -0,0 +1 @@
+in tls_callback