Move metadata symbol export from exported_non_generic_symbols to exported_symbols

The metadata symbol must not be encoded in the crate metadata, and must
be exported from proc-macros. Handling the export of the metadata symbol
in exported_symbols handles both things at once without requiring manual
fixups elsewhere.

Author: bjorn3

compiler/rustc_codegen_ssa/src/back/linker.rs

@@ -1805,11 +1805,18 @@ pub(crate) fn exported_symbols(
             .collect();
     }
 
-    if let CrateType::ProcMacro = crate_type {
+    let mut symbols = if let CrateType::ProcMacro = crate_type {
         exported_symbols_for_proc_macro_crate(tcx)
     } else {
         exported_symbols_for_non_proc_macro(tcx, crate_type)
+    };
+
+    if crate_type == CrateType::Dylib || crate_type == CrateType::ProcMacro {
+        let metadata_symbol_name = exported_symbols::metadata_symbol_name(tcx);
+        symbols.push((metadata_symbol_name, SymbolExportKind::Data));
     }
+
+    symbols
 }
 
 fn exported_symbols_for_non_proc_macro(
@@ -1842,12 +1849,8 @@ fn exported_symbols_for_proc_macro_crate(tcx: TyCtxt<'_>) -> Vec<(String, Symbol
 
     let stable_crate_id = tcx.stable_crate_id(LOCAL_CRATE);
     let proc_macro_decls_name = tcx.sess.generate_proc_macro_decls_symbol(stable_crate_id);
-    let metadata_symbol_name = exported_symbols::metadata_symbol_name(tcx);
 
-    vec![
-        (proc_macro_decls_name, SymbolExportKind::Data),
-        (metadata_symbol_name, SymbolExportKind::Data),
-    ]
+    vec![(proc_macro_decls_name, SymbolExportKind::Data)]
 }
 
 pub(crate) fn linked_symbols(

compiler/rustc_codegen_ssa/src/back/symbol_export.rs

@@ -8,7 +8,7 @@ use rustc_hir::def_id::{CrateNum, DefId, DefIdMap, LOCAL_CRATE, LocalDefId};
 use rustc_middle::bug;
 use rustc_middle::middle::codegen_fn_attrs::CodegenFnAttrFlags;
 use rustc_middle::middle::exported_symbols::{
-    ExportedSymbol, SymbolExportInfo, SymbolExportKind, SymbolExportLevel, metadata_symbol_name,
+    ExportedSymbol, SymbolExportInfo, SymbolExportKind, SymbolExportLevel,
 };
 use rustc_middle::query::LocalCrate;
 use rustc_middle::ty::{self, GenericArgKind, GenericArgsRef, Instance, SymbolName, Ty, TyCtxt};
@@ -289,23 +289,6 @@ fn exported_non_generic_symbols_provider_local<'tcx>(
         }));
     }
 
-    if tcx.crate_types().contains(&CrateType::Dylib)
-        || tcx.crate_types().contains(&CrateType::ProcMacro)
-    {
-        let symbol_name = metadata_symbol_name(tcx);
-        let exported_symbol = ExportedSymbol::NoDefId(SymbolName::new(tcx, &symbol_name));
-
-        symbols.push((
-            exported_symbol,
-            SymbolExportInfo {
-                level: SymbolExportLevel::C,
-                kind: SymbolExportKind::Data,
-                used: true,
-                rustc_std_internal_symbol: false,
-            },
-        ));
-    }
-
     // Sort so we get a stable incr. comp. hash.
     symbols.sort_by_cached_key(|s| s.0.symbol_name_for_local_instance(tcx));
 

compiler/rustc_metadata/src/rmeta/encoder.rs

@@ -19,13 +19,12 @@ use rustc_hir::find_attr;
 use rustc_hir_pretty::id_to_string;
 use rustc_middle::dep_graph::WorkProductId;
 use rustc_middle::middle::dependency_format::Linkage;
-use rustc_middle::middle::exported_symbols::metadata_symbol_name;
 use rustc_middle::mir::interpret;
 use rustc_middle::query::Providers;
 use rustc_middle::traits::specialization_graph;
+use rustc_middle::ty::AssocItemContainer;
 use rustc_middle::ty::codec::TyEncoder;
 use rustc_middle::ty::fast_reject::{self, TreatParams};
-use rustc_middle::ty::{AssocItemContainer, SymbolName};
 use rustc_middle::{bug, span_bug};
 use rustc_serialize::{Decodable, Decoder, Encodable, Encoder, opaque};
 use rustc_session::config::{CrateType, OptLevel, TargetModifier};
@@ -2207,19 +2206,8 @@ impl<'a, 'tcx> EncodeContext<'a, 'tcx> {
         exported_symbols: &[(ExportedSymbol<'tcx>, SymbolExportInfo)],
     ) -> LazyArray<(ExportedSymbol<'static>, SymbolExportInfo)> {
         empty_proc_macro!(self);
-        // The metadata symbol name is special. It should not show up in
-        // downstream crates.
-        let metadata_symbol_name = SymbolName::new(self.tcx, &metadata_symbol_name(self.tcx));
 
-        self.lazy_array(
-            exported_symbols
-                .iter()
-                .filter(|&(exported_symbol, _)| match *exported_symbol {
-                    ExportedSymbol::NoDefId(symbol_name) => symbol_name != metadata_symbol_name,
-                    _ => true,
-                })
-                .cloned(),
-        )
+        self.lazy_array(exported_symbols.iter().cloned())
     }
 
     fn encode_dylib_dependency_formats(&mut self) -> LazyArray<Option<LinkagePreference>> {