Rollup merge of #64324 - alexcrichton:share-generics-again, r=michaelwoerister

rustc: Fix mixing crates with different `share_generics`

This commit addresses #64319 by removing the `dylib` crate type from the
list of crate type that exports generic symbols. The bug in #64319
arises because a `dylib` crate type was trying to export a symbol in an
uptream crate but it miscalculated the symbol name of the uptream
symbol. This isn't really necessary, though, since `dylib` crates aren't
that heavily used, so we can just conservatively say that the `dylib`
crate type never exports generic symbols, forcibly removing them from
the exported symbol lists if were to otherwise find them.

The fix here happens in two places:

* First is in the `local_crate_exports_generics` method, indicating that
  it's now `false` for the `Dylib` crate type. Only rlibs actually
  export generics at this point.

* Next is when we load exported symbols from upstream crate. If, for our
  compilation session, the crate may be included from a dynamic library,
  then its generic symbols are removed. When the crate was linked into a
  dynamic library its symbols weren't exported, so we can't consider
  them a candidate to link against.

Overally this should avoid situations where we incorrectly calculate the
upstream symbol names in the face of differnet `share_generics` options,
ultimately...

Closes #64319

6 files changed, 74 insertions, 30 deletions

diff --git a/src/librustc_codegen_ssa/back/link.rs b/src/librustc_codegen_ssa/back/link.rs
index 9b044d9b453..3b7ae5e33d5 100644
--- a/src/librustc_codegen_ssa/back/link.rs
+++ b/src/librustc_codegen_ssa/back/link.rs
@@ -219,15 +219,24 @@ pub fn get_linker(sess: &Session, linker: &Path, flavor: LinkerFlavor) -> (PathB
     (linker.to_path_buf(), cmd)
 }
 
-pub fn each_linked_rlib(sess: &Session,
-                               info: &CrateInfo,
-                               f: &mut dyn FnMut(CrateNum, &Path)) -> Result<(), String> {
+pub fn each_linked_rlib(
+    info: &CrateInfo,
+    f: &mut dyn FnMut(CrateNum, &Path),
+) -> Result<(), String> {
     let crates = info.used_crates_static.iter();
-    let fmts = sess.dependency_formats.borrow();
-    let fmts = fmts.get(&config::CrateType::Executable)
-                   .or_else(|| fmts.get(&config::CrateType::Staticlib))
-                   .or_else(|| fmts.get(&config::CrateType::Cdylib))
-                   .or_else(|| fmts.get(&config::CrateType::ProcMacro));
+    let mut fmts = None;
+    for (ty, list) in info.dependency_formats.iter() {
+        match ty {
+            config::CrateType::Executable |
+            config::CrateType::Staticlib |
+            config::CrateType::Cdylib |
+            config::CrateType::ProcMacro => {
+                fmts = Some(list);
+                break;
+            }
+            _ => {}
+        }
+    }
     let fmts = match fmts {
         Some(f) => f,
         None => return Err("could not find formats for rlibs".to_string())
@@ -406,7 +415,7 @@ fn link_staticlib<'a, B: ArchiveBuilder<'a>>(sess: &'a Session,
                            tempdir);
     let mut all_native_libs = vec![];
 
-    let res = each_linked_rlib(sess, &codegen_results.crate_info, &mut |cnum, path| {
+    let res = each_linked_rlib(&codegen_results.crate_info, &mut |cnum, path| {
         let name = &codegen_results.crate_info.crate_name[&cnum];
         let native_libs = &codegen_results.crate_info.native_libraries[&cnum];
 
@@ -1294,11 +1303,13 @@ pub fn add_local_native_libraries(cmd: &mut dyn Linker,
 // Rust crates are not considered at all when creating an rlib output. All
 // dependencies will be linked when producing the final output (instead of
 // the intermediate rlib version)
-fn add_upstream_rust_crates<'a, B: ArchiveBuilder<'a>>(cmd: &mut dyn Linker,
-                            sess: &'a Session,
-                            codegen_results: &CodegenResults,
-                            crate_type: config::CrateType,
-                            tmpdir: &Path) {
+fn add_upstream_rust_crates<'a, B: ArchiveBuilder<'a>>(
+    cmd: &mut dyn Linker,
+    sess: &'a Session,
+    codegen_results: &CodegenResults,
+    crate_type: config::CrateType,
+    tmpdir: &Path,
+) {
     // All of the heavy lifting has previously been accomplished by the
     // dependency_format module of the compiler. This is just crawling the
     // output of that module, adding crates as necessary.
@@ -1307,8 +1318,10 @@ fn add_upstream_rust_crates<'a, B: ArchiveBuilder<'a>>(cmd: &mut dyn Linker,
     // will slurp up the object files inside), and linking to a dynamic library
     // involves just passing the right -l flag.
 
-    let formats = sess.dependency_formats.borrow();
-    let data = formats.get(&crate_type).unwrap();
+    let (_, data) = codegen_results.crate_info.dependency_formats
+        .iter()
+        .find(|(ty, _)| *ty == crate_type)
+        .expect("failed to find crate type in dependency format list");
 
     // Invoke get_used_crates to ensure that we get a topological sorting of
     // crates.
@@ -1620,10 +1633,12 @@ fn add_upstream_rust_crates<'a, B: ArchiveBuilder<'a>>(cmd: &mut dyn Linker,
 // generic function calls a native function, then the generic function must
 // be instantiated in the target crate, meaning that the native symbol must
 // also be resolved in the target crate.
-pub fn add_upstream_native_libraries(cmd: &mut dyn Linker,
-                                 sess: &Session,
-                                 codegen_results: &CodegenResults,
-                                 crate_type: config::CrateType) {
+pub fn add_upstream_native_libraries(
+    cmd: &mut dyn Linker,
+    sess: &Session,
+    codegen_results: &CodegenResults,
+    crate_type: config::CrateType,
+) {
     // Be sure to use a topological sorting of crates because there may be
     // interdependencies between native libraries. When passing -nodefaultlibs,
     // for example, almost all native libraries depend on libc, so we have to
@@ -1633,8 +1648,10 @@ pub fn add_upstream_native_libraries(cmd: &mut dyn Linker,
     // This passes RequireStatic, but the actual requirement doesn't matter,
     // we're just getting an ordering of crate numbers, we're not worried about
     // the paths.
-    let formats = sess.dependency_formats.borrow();
-    let data = formats.get(&crate_type).unwrap();
+    let (_, data) = codegen_results.crate_info.dependency_formats
+        .iter()
+        .find(|(ty, _)| *ty == crate_type)
+        .expect("failed to find crate type in dependency format list");
 
     let crates = &codegen_results.crate_info.used_crates_static;
     for &(cnum, _) in crates {
diff --git a/src/librustc_codegen_ssa/back/linker.rs b/src/librustc_codegen_ssa/back/linker.rs
index c42cd024926..ff87f0b1547 100644
--- a/src/librustc_codegen_ssa/back/linker.rs
+++ b/src/librustc_codegen_ssa/back/linker.rs
@@ -14,6 +14,7 @@ use rustc::middle::dependency_format::Linkage;
 use rustc::session::Session;
 use rustc::session::config::{self, CrateType, OptLevel, DebugInfo,
                              LinkerPluginLto, Lto};
+use rustc::middle::exported_symbols::ExportedSymbol;
 use rustc::ty::TyCtxt;
 use rustc_target::spec::{LinkerFlavor, LldFlavor};
 use rustc_serialize::{json, Encoder};
@@ -1092,18 +1093,41 @@ fn exported_symbols(tcx: TyCtxt<'_>, crate_type: CrateType) -> Vec<String> {
         }
     }
 
-    let formats = tcx.sess.dependency_formats.borrow();
-    let deps = formats[&crate_type].iter();
+    let formats = tcx.dependency_formats(LOCAL_CRATE);
+    let deps = formats.iter().filter_map(|(t, list)| {
+        if *t == crate_type {
+            Some(list)
+        } else {
+            None
+        }
+    }).next().unwrap();
 
-    for (index, dep_format) in deps.enumerate() {
+    for (index, dep_format) in deps.iter().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.
             for &(symbol, level) in tcx.exported_symbols(cnum).iter() {
-                if level.is_below_threshold(export_threshold) {
-                    symbols.push(symbol.symbol_name(tcx).to_string());
+                if !level.is_below_threshold(export_threshold) {
+                    continue;
                 }
+
+                // Do not export generic symbols from upstream crates in linked
+                // artifact (notably the `dylib` crate type). The main reason
+                // for this is that `symbol_name` is actually wrong for generic
+                // symbols because it guesses the name we'd give them locally
+                // rather than the name it has upstream (depending on
+                // `share_generics` settings and such).
+                //
+                // To fix that issue we just say that linked artifacts, aka
+                // `dylib`s, never export generic symbols and they aren't
+                // available to downstream crates. (the not available part is
+                // handled elsewhere).
+                if let ExportedSymbol::Generic(..) = symbol {
+                    continue;
+                }
+
+                symbols.push(symbol.symbol_name(tcx).to_string());
             }
         }
     }
diff --git a/src/librustc_codegen_ssa/back/symbol_export.rs b/src/librustc_codegen_ssa/back/symbol_export.rs
index 7e700e68194..3e4b7695447 100644
--- a/src/librustc_codegen_ssa/back/symbol_export.rs
+++ b/src/librustc_codegen_ssa/back/symbol_export.rs
@@ -298,7 +298,7 @@ fn upstream_monomorphizations_provider(
     };
 
     for &cnum in cnums.iter() {
-        for &(ref exported_symbol, _) in tcx.exported_symbols(cnum).iter() {
+        for (exported_symbol, _) in tcx.exported_symbols(cnum).iter() {
             if let &ExportedSymbol::Generic(def_id, substs) = exported_symbol {
                 let substs_map = instances.entry(def_id).or_default();
 
diff --git a/src/librustc_codegen_ssa/back/write.rs b/src/librustc_codegen_ssa/back/write.rs
index 1bba479c1fd..1a2c23ae0d4 100644
--- a/src/librustc_codegen_ssa/back/write.rs
+++ b/src/librustc_codegen_ssa/back/write.rs
@@ -1048,7 +1048,7 @@ fn start_executing_work<B: ExtraBackendMethods>(
     }).expect("failed to spawn helper thread");
 
     let mut each_linked_rlib_for_lto = Vec::new();
-    drop(link::each_linked_rlib(sess, crate_info, &mut |cnum, path| {
+    drop(link::each_linked_rlib(crate_info, &mut |cnum, path| {
         if link::ignored_for_lto(sess, crate_info, cnum) {
             return
         }
diff --git a/src/librustc_codegen_ssa/base.rs b/src/librustc_codegen_ssa/base.rs
index 4acbe0356b4..98d3022a418 100644
--- a/src/librustc_codegen_ssa/base.rs
+++ b/src/librustc_codegen_ssa/base.rs
@@ -539,7 +539,7 @@ pub fn codegen_crate<B: ExtraBackendMethods>(
     // linkage, then it's already got an allocator shim and we'll be using that
     // one instead. If nothing exists then it's our job to generate the
     // allocator!
-    let any_dynamic_crate = tcx.sess.dependency_formats.borrow()
+    let any_dynamic_crate = tcx.dependency_formats(LOCAL_CRATE)
         .iter()
         .any(|(_, list)| {
             use rustc::middle::dependency_format::Linkage;
@@ -731,6 +731,7 @@ impl CrateInfo {
             used_crate_source: Default::default(),
             lang_item_to_crate: Default::default(),
             missing_lang_items: Default::default(),
+            dependency_formats: tcx.dependency_formats(LOCAL_CRATE),
         };
         let lang_items = tcx.lang_items();
 
diff --git a/src/librustc_codegen_ssa/lib.rs b/src/librustc_codegen_ssa/lib.rs
index 1708d7235b4..161d3ce61f0 100644
--- a/src/librustc_codegen_ssa/lib.rs
+++ b/src/librustc_codegen_ssa/lib.rs
@@ -33,6 +33,7 @@ use rustc_data_structures::fx::{FxHashMap, FxHashSet};
 use rustc_data_structures::sync::Lrc;
 use rustc_data_structures::svh::Svh;
 use rustc::middle::cstore::{LibSource, CrateSource, NativeLibrary};
+use rustc::middle::dependency_format::Dependencies;
 use syntax_pos::symbol::Symbol;
 
 mod error_codes;
@@ -142,6 +143,7 @@ pub struct CrateInfo {
     pub used_crates_dynamic: Vec<(CrateNum, LibSource)>,
     pub lang_item_to_crate: FxHashMap<LangItem, CrateNum>,
     pub missing_lang_items: FxHashMap<CrateNum, Vec<LangItem>>,
+    pub dependency_formats: Lrc<Dependencies>,
 }