Auto merge of #38117 - michaelwoerister:hidden-symbols, r=alexcrichton

Improve symbol visibility handling for dynamic libraries.

This will hopefully fix issue #37530 and maybe also #32887.

I'm relying on @m4b to post some numbers on how awesome the improvement for cdylibs is `:)`

cc @rust-lang/compiler @rust-lang/tools @cuviper @froydnj
r? @alexcrichton

src/librustc/middle/cstore.rs

@@ -328,8 +328,9 @@ pub trait CrateStore<'tcx> {
     fn crate_hash(&self, cnum: CrateNum) -> Svh;
     fn crate_disambiguator(&self, cnum: CrateNum) -> Symbol;
     fn plugin_registrar_fn(&self, cnum: CrateNum) -> Option<DefId>;
+    fn derive_registrar_fn(&self, cnum: CrateNum) -> Option<DefId>;
     fn native_libraries(&self, cnum: CrateNum) -> Vec<NativeLibrary>;
-    fn reachable_ids(&self, cnum: CrateNum) -> Vec<DefId>;
+    fn exported_symbols(&self, cnum: CrateNum) -> Vec<DefId>;
     fn is_no_builtins(&self, cnum: CrateNum) -> bool;
 
     // resolve
@@ -491,9 +492,11 @@ impl<'tcx> CrateStore<'tcx> for DummyCrateStore {
                            -> Symbol { bug!("crate_disambiguator") }
     fn plugin_registrar_fn(&self, cnum: CrateNum) -> Option<DefId>
         { bug!("plugin_registrar_fn") }
+    fn derive_registrar_fn(&self, cnum: CrateNum) -> Option<DefId>
+        { bug!("derive_registrar_fn") }
     fn native_libraries(&self, cnum: CrateNum) -> Vec<NativeLibrary>
         { bug!("native_libraries") }
-    fn reachable_ids(&self, cnum: CrateNum) -> Vec<DefId> { bug!("reachable_ids") }
+    fn exported_symbols(&self, cnum: CrateNum) -> Vec<DefId> { bug!("exported_symbols") }
     fn is_no_builtins(&self, cnum: CrateNum) -> bool { bug!("is_no_builtins") }
 
     // resolve

src/librustc_llvm/ffi.rs

@@ -64,6 +64,15 @@ pub enum Linkage {
     CommonLinkage = 10,
 }
 
+// LLVMRustVisibility
+#[derive(Copy, Clone, PartialEq, Eq, Hash, Debug)]
+#[repr(C)]
+pub enum Visibility {
+    Default = 0,
+    Hidden = 1,
+    Protected = 2,
+}
+
 /// LLVMDiagnosticSeverity
 #[derive(Copy, Clone, Debug)]
 #[repr(C)]
@@ -399,13 +408,6 @@ pub type OperandBundleDefRef = *mut OperandBundleDef_opaque;
 pub type DiagnosticHandler = unsafe extern "C" fn(DiagnosticInfoRef, *mut c_void);
 pub type InlineAsmDiagHandler = unsafe extern "C" fn(SMDiagnosticRef, *const c_void, c_uint);
 
-/// LLVMVisibility
-#[repr(C)]
-pub enum Visibility {
-    Default,
-    Hidden,
-    Protected,
-}
 
 pub mod debuginfo {
     use super::MetadataRef;
@@ -655,7 +657,8 @@ extern "C" {
     pub fn LLVMRustSetLinkage(Global: ValueRef, RustLinkage: Linkage);
     pub fn LLVMGetSection(Global: ValueRef) -> *const c_char;
     pub fn LLVMSetSection(Global: ValueRef, Section: *const c_char);
-    pub fn LLVMSetVisibility(Global: ValueRef, Viz: Visibility);
+    pub fn LLVMRustGetVisibility(Global: ValueRef) -> Visibility;
+    pub fn LLVMRustSetVisibility(Global: ValueRef, Viz: Visibility);
     pub fn LLVMGetAlignment(Global: ValueRef) -> c_uint;
     pub fn LLVMSetAlignment(Global: ValueRef, Bytes: c_uint);
     pub fn LLVMSetDLLStorageClass(V: ValueRef, C: DLLStorageClass);

src/librustc_metadata/cstore_impl.rs

@@ -306,14 +306,22 @@ impl<'tcx> CrateStore<'tcx> for cstore::CStore {
         })
     }
 
+    fn derive_registrar_fn(&self, cnum: CrateNum) -> Option<DefId>
+    {
+        self.get_crate_data(cnum).root.macro_derive_registrar.map(|index| DefId {
+            krate: cnum,
+            index: index
+        })
+    }
+
     fn native_libraries(&self, cnum: CrateNum) -> Vec<NativeLibrary>
     {
         self.get_crate_data(cnum).get_native_libraries()
     }
 
-    fn reachable_ids(&self, cnum: CrateNum) -> Vec<DefId>
+    fn exported_symbols(&self, cnum: CrateNum) -> Vec<DefId>
     {
-        self.get_crate_data(cnum).get_reachable_ids()
+        self.get_crate_data(cnum).get_exported_symbols()
     }
 
     fn is_no_builtins(&self, cnum: CrateNum) -> bool {

src/librustc_metadata/decoder.rs

@@ -1038,8 +1038,8 @@ impl<'a, 'tcx> CrateMetadata {
         arg_names.decode(self).collect()
     }
 
-    pub fn get_reachable_ids(&self) -> Vec<DefId> {
-        self.root.reachable_ids.decode(self).map(|index| self.local_def_id(index)).collect()
+    pub fn get_exported_symbols(&self) -> Vec<DefId> {
+        self.root.exported_symbols.decode(self).map(|index| self.local_def_id(index)).collect()
     }
 
     pub fn get_macro(&self, id: DefIndex) -> (ast::Name, MacroDef) {

src/librustc_metadata/encoder.rs

@@ -50,7 +50,7 @@ pub struct EncodeContext<'a, 'tcx: 'a> {
     reexports: &'a def::ExportMap,
     link_meta: &'a LinkMeta,
     cstore: &'a cstore::CStore,
-    reachable: &'a NodeSet,
+    exported_symbols: &'a NodeSet,
 
     lazy_state: LazyState,
     type_shorthands: FxHashMap<Ty<'tcx>, usize>,
@@ -1223,16 +1223,16 @@ impl<'a, 'tcx> EncodeContext<'a, 'tcx> {
         self.lazy_seq(all_impls)
     }
 
-    // Encodes all reachable symbols in this crate into the metadata.
+    // Encodes all symbols exported from this crate into the metadata.
     //
     // This pass is seeded off the reachability list calculated in the
     // middle::reachable module but filters out items that either don't have a
     // symbol associated with them (they weren't translated) or if they're an FFI
     // definition (as that's not defined in this crate).
-    fn encode_reachable(&mut self) -> LazySeq<DefIndex> {
-        let reachable = self.reachable;
+    fn encode_exported_symbols(&mut self) -> LazySeq<DefIndex> {
+        let exported_symbols = self.exported_symbols;
         let tcx = self.tcx;
-        self.lazy_seq(reachable.iter().map(|&id| tcx.map.local_def_id(id).index))
+        self.lazy_seq(exported_symbols.iter().map(|&id| tcx.map.local_def_id(id).index))
     }
 
     fn encode_dylib_dependency_formats(&mut self) -> LazySeq<Option<LinkagePreference>> {
@@ -1278,10 +1278,10 @@ impl<'a, 'tcx> EncodeContext<'a, 'tcx> {
         let impls = self.encode_impls();
         let impl_bytes = self.position() - i;
 
-        // Encode reachability info.
+        // Encode exported symbols info.
         i = self.position();
-        let reachable_ids = self.encode_reachable();
-        let reachable_bytes = self.position() - i;
+        let exported_symbols = self.encode_exported_symbols();
+        let exported_symbols_bytes = self.position() - i;
 
         // Encode and index the items.
         i = self.position();
@@ -1319,7 +1319,7 @@ impl<'a, 'tcx> EncodeContext<'a, 'tcx> {
             native_libraries: native_libraries,
             codemap: codemap,
             impls: impls,
-            reachable_ids: reachable_ids,
+            exported_symbols: exported_symbols,
             index: index,
         });
 
@@ -1339,7 +1339,7 @@ impl<'a, 'tcx> EncodeContext<'a, 'tcx> {
             println!("          native bytes: {}", native_lib_bytes);
             println!("         codemap bytes: {}", codemap_bytes);
             println!("            impl bytes: {}", impl_bytes);
-            println!("       reachable bytes: {}", reachable_bytes);
+            println!("    exp. symbols bytes: {}", exported_symbols_bytes);
             println!("            item bytes: {}", item_bytes);
             println!("           index bytes: {}", index_bytes);
             println!("            zero bytes: {}", zero_bytes);
@@ -1377,7 +1377,7 @@ pub fn encode_metadata<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>,
                                  cstore: &cstore::CStore,
                                  reexports: &def::ExportMap,
                                  link_meta: &LinkMeta,
-                                 reachable: &NodeSet)
+                                 exported_symbols: &NodeSet)
                                  -> Vec<u8> {
     let mut cursor = Cursor::new(vec![]);
     cursor.write_all(METADATA_HEADER).unwrap();
@@ -1392,7 +1392,7 @@ pub fn encode_metadata<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>,
             reexports: reexports,
             link_meta: link_meta,
             cstore: cstore,
-            reachable: reachable,
+            exported_symbols: exported_symbols,
             lazy_state: LazyState::NoNode,
             type_shorthands: Default::default(),
             predicate_shorthands: Default::default(),

src/librustc_metadata/schema.rs

@@ -180,7 +180,7 @@ pub struct CrateRoot {
     pub native_libraries: LazySeq<NativeLibrary>,
     pub codemap: LazySeq<syntax_pos::FileMap>,
     pub impls: LazySeq<TraitImpls>,
-    pub reachable_ids: LazySeq<DefIndex>,
+    pub exported_symbols: LazySeq<DefIndex>,
     pub index: LazySeq<index::Index>,
 }
 

src/librustc_trans/back/linker.rs

@@ -17,11 +17,11 @@ use std::path::{Path, PathBuf};
 use std::process::Command;
 
 use context::SharedCrateContext;
-use monomorphize::Instance;
 
 use back::archive;
+use back::symbol_export::{self, ExportedSymbols};
 use middle::dependency_format::Linkage;
-use rustc::hir::def_id::CrateNum;
+use rustc::hir::def_id::{LOCAL_CRATE, CrateNum};
 use session::Session;
 use session::config::CrateType;
 use session::config;
@@ -34,10 +34,10 @@ pub struct LinkerInfo {
 
 impl<'a, 'tcx> LinkerInfo {
     pub fn new(scx: &SharedCrateContext<'a, 'tcx>,
-               reachable: &[String]) -> LinkerInfo {
+               exports: &ExportedSymbols) -> LinkerInfo {
         LinkerInfo {
             exports: scx.sess().crate_types.borrow().iter().map(|&c| {
-                (c, exported_symbols(scx, reachable, c))
+                (c, exported_symbols(scx, exports, c))
             }).collect(),
         }
     }
@@ -253,46 +253,47 @@ impl<'a> Linker for GnuLinker<'a> {
         let mut arg = OsString::new();
         let path = tmpdir.join("list");
 
-        if self.sess.target.target.options.is_like_solaris {
+        debug!("EXPORTED SYMBOLS:");
+
+        if self.sess.target.target.options.is_like_osx {
+            // Write a plain, newline-separated list of symbols
             let res = (|| -> io::Result<()> {
                 let mut f = BufWriter::new(File::create(&path)?);
-                writeln!(f, "{{\n  global:")?;
                 for sym in self.info.exports[&crate_type].iter() {
-                    writeln!(f, "    {};", sym)?;
+                    debug!("  _{}", sym);
+                    writeln!(f, "_{}", sym)?;
                 }
-                writeln!(f, "\n  local:\n    *;\n}};")?;
                 Ok(())
             })();
             if let Err(e) = res {
-                self.sess.fatal(&format!("failed to write version script: {}", e));
+                self.sess.fatal(&format!("failed to write lib.def file: {}", e));
             }
-
-            arg.push("-Wl,-M,");
-            arg.push(&path);
         } else {
-            let prefix = if self.sess.target.target.options.is_like_osx {
-                "_"
-            } else {
-                ""
-            };
+            // Write an LD version script
             let res = (|| -> io::Result<()> {
                 let mut f = BufWriter::new(File::create(&path)?);
+                writeln!(f, "{{\n  global:")?;
                 for sym in self.info.exports[&crate_type].iter() {
-                    writeln!(f, "{}{}", prefix, sym)?;
+                    debug!("    {};", sym);
+                    writeln!(f, "    {};", sym)?;
                 }
+                writeln!(f, "\n  local:\n    *;\n}};")?;
                 Ok(())
             })();
             if let Err(e) = res {
-                self.sess.fatal(&format!("failed to write lib.def file: {}", e));
-            }
-            if self.sess.target.target.options.is_like_osx {
-                arg.push("-Wl,-exported_symbols_list,");
-            } else {
-                arg.push("-Wl,--retain-symbols-file=");
+                self.sess.fatal(&format!("failed to write version script: {}", e));
             }
-            arg.push(&path);
         }
 
+        if self.sess.target.target.options.is_like_osx {
+            arg.push("-Wl,-exported_symbols_list,");
+        } else if self.sess.target.target.options.is_like_solaris {
+            arg.push("-Wl,-M,");
+        } else {
+            arg.push("-Wl,--version-script=");
+        }
+
+        arg.push(&path);
         self.cmd.arg(arg);
     }
 
@@ -473,43 +474,29 @@ impl<'a> Linker for MsvcLinker<'a> {
 }
 
 fn exported_symbols(scx: &SharedCrateContext,
-                    reachable: &[String],
+                    exported_symbols: &ExportedSymbols,
                     crate_type: CrateType)
                     -> Vec<String> {
-    // See explanation in GnuLinker::export_symbols, for
-    // why we don't ever need dylib symbols on non-MSVC.
-    if crate_type == CrateType::CrateTypeDylib ||
-       crate_type == CrateType::CrateTypeProcMacro {
-        if !scx.sess().target.target.options.is_like_msvc {
-            return vec![];
-        }
-    }
+    let export_threshold = symbol_export::crate_export_threshold(crate_type);
 
-    let mut symbols = reachable.to_vec();
+    let mut symbols = Vec::new();
+    exported_symbols.for_each_exported_symbol(LOCAL_CRATE, export_threshold, |name, _| {
+        symbols.push(name.to_owned());
+    });
 
-    // If we're producing anything other than a dylib then the `reachable` array
-    // above is the exhaustive set of symbols we should be exporting.
-    //
-    // For dylibs, however, we need to take a look at how all upstream crates
-    // are linked into this dynamic library. For all statically linked
-    // libraries we take all their reachable symbols and emit them as well.
-    if crate_type != CrateType::CrateTypeDylib {
-        return symbols
-    }
-
-    let cstore = &scx.sess().cstore;
     let formats = scx.sess().dependency_formats.borrow();
     let deps = formats[&crate_type].iter();
-    symbols.extend(deps.enumerate().filter_map(|(i, f)| {
-        if *f == Linkage::Static {
-            Some(CrateNum::new(i + 1))
-        } else {
-            None
+
+    for (index, dep_format) in deps.enumerate() {
+        let cnum = CrateNum::new(index + 1);
+        // For each dependency that we are linking to statically ...
+        if *dep_format == Linkage::Static {
+            // ... we add its symbol list to our export list.
+            exported_symbols.for_each_exported_symbol(cnum, export_threshold, |name, _| {
+                symbols.push(name.to_owned());
+            })
         }
-    }).flat_map(|cnum| {
-        cstore.reachable_ids(cnum)
-    }).map(|did| -> String {
-        Instance::mono(scx, did).symbol_name(scx)
-    }));
+    }
+
     symbols
 }