Don't show crate metadata symbol as exported symbol to downstream crates.

src/librustc/middle/exported_symbols.rs

@@ -8,7 +8,7 @@
 // option. This file may not be copied, modified, or distributed
 // except according to those terms.
 
-use hir::def_id::DefId;
+use hir::def_id::{DefId, LOCAL_CRATE};
 use std::cmp;
 use ty;
 
@@ -87,3 +87,9 @@ impl_stable_hash_for!(enum self::ExportedSymbol {
     NonGeneric(def_id),
     NoDefId(symbol_name)
 });
+
+pub fn metadata_symbol_name(tcx: ty::TyCtxt) -> String {
+    format!("rust_metadata_{}_{}",
+            tcx.original_crate_name(LOCAL_CRATE),
+            tcx.crate_disambiguator(LOCAL_CRATE).to_fingerprint().to_hex())
+}

src/librustc_metadata/encoder.rs

@@ -20,11 +20,12 @@ use rustc::hir::def_id::{CrateNum, CRATE_DEF_INDEX, DefIndex, DefId, LOCAL_CRATE
 use rustc::hir::map::definitions::DefPathTable;
 use rustc::ich::Fingerprint;
 use rustc::middle::dependency_format::Linkage;
-use rustc::middle::exported_symbols::{ExportedSymbol, SymbolExportLevel};
+use rustc::middle::exported_symbols::{ExportedSymbol, SymbolExportLevel,
+                                      metadata_symbol_name};
 use rustc::middle::lang_items;
 use rustc::mir;
 use rustc::traits::specialization_graph;
-use rustc::ty::{self, Ty, TyCtxt, ReprOptions};
+use rustc::ty::{self, Ty, TyCtxt, ReprOptions, SymbolName};
 use rustc::ty::codec::{self as ty_codec, TyEncoder};
 
 use rustc::session::config::{self, CrateTypeProcMacro};
@@ -1392,7 +1393,22 @@ impl<'a, 'b: 'a, 'tcx: 'b> IsolatedEncoder<'a, 'b, 'tcx> {
     fn encode_exported_symbols(&mut self,
                                exported_symbols: &[(ExportedSymbol, SymbolExportLevel)])
                                -> LazySeq<(ExportedSymbol, SymbolExportLevel)> {
-        self.lazy_seq(exported_symbols.iter().cloned())
+
+        // The metadata symbol name is special. It should not show up in
+        // downstream crates.
+        let metadata_symbol_name = SymbolName::new(&metadata_symbol_name(self.tcx));
+
+        self.lazy_seq(exported_symbols
+            .iter()
+            .filter(|&&(ref exported_symbol, _)| {
+                match *exported_symbol {
+                    ExportedSymbol::NoDefId(symbol_name) => {
+                        symbol_name != metadata_symbol_name
+                    },
+                    _ => true,
+                }
+            })
+            .cloned())
     }
 
     fn encode_dylib_dependency_formats(&mut self, _: ()) -> LazySeq<Option<LinkagePreference>> {

src/librustc_trans/back/symbol_export.rs

@@ -15,7 +15,7 @@ use monomorphize::Instance;
 use rustc::hir;
 use rustc::hir::def_id::CrateNum;
 use rustc::hir::def_id::{DefId, LOCAL_CRATE};
-use rustc::middle::exported_symbols::{SymbolExportLevel, ExportedSymbol};
+use rustc::middle::exported_symbols::{SymbolExportLevel, ExportedSymbol, metadata_symbol_name};
 use rustc::session::config;
 use rustc::ty::{TyCtxt, SymbolName};
 use rustc::ty::maps::Providers;
@@ -32,12 +32,6 @@ pub fn threshold(tcx: TyCtxt) -> SymbolExportLevel {
     crates_export_threshold(&tcx.sess.crate_types.borrow())
 }
 
-pub fn metadata_symbol_name(tcx: TyCtxt) -> String {
-    format!("rust_metadata_{}_{}",
-            tcx.crate_name(LOCAL_CRATE),
-            tcx.crate_disambiguator(LOCAL_CRATE).to_fingerprint().to_hex())
-}
-
 fn crate_export_threshold(crate_type: config::CrateType) -> SymbolExportLevel {
     match crate_type {
         config::CrateTypeExecutable |

src/librustc_trans/base.rs

@@ -30,7 +30,6 @@ use super::ModuleKind;
 
 use abi;
 use back::link;
-use back::symbol_export;
 use back::write::{self, OngoingCrateTranslation, create_target_machine};
 use llvm::{ContextRef, ModuleRef, ValueRef, Vector, get_param};
 use llvm;
@@ -45,6 +44,7 @@ use rustc::ty::maps::Providers;
 use rustc::dep_graph::{DepNode, DepConstructor};
 use rustc::ty::subst::Kind;
 use rustc::middle::cstore::{self, LinkMeta, LinkagePreference};
+use rustc::middle::exported_symbols;
 use rustc::util::common::{time, print_time_passes_entry};
 use rustc::session::config::{self, NoDebugInfo};
 use rustc::session::Session;
@@ -654,7 +654,7 @@ fn write_metadata<'a, 'gcx>(tcx: TyCtxt<'a, 'gcx, 'gcx>,
 
     let llmeta = C_bytes_in_context(metadata_llcx, &compressed);
     let llconst = C_struct_in_context(metadata_llcx, &[llmeta], false);
-    let name = symbol_export::metadata_symbol_name(tcx);
+    let name = exported_symbols::metadata_symbol_name(tcx);
     let buf = CString::new(name).unwrap();
     let llglobal = unsafe {
         llvm::LLVMAddGlobal(metadata_llmod, val_ty(llconst).to_ref(), buf.as_ptr())