Mark __msan_track_origins as an exported symbol for LTO

Author: nikic

src/librustc_codegen_ssa/back/symbol_export.rs

@@ -3,7 +3,7 @@ use std::sync::Arc;
 
 use rustc::middle::codegen_fn_attrs::CodegenFnAttrFlags;
 use rustc::middle::exported_symbols::{metadata_symbol_name, ExportedSymbol, SymbolExportLevel};
-use rustc::session::config;
+use rustc::session::config::{self, Sanitizer};
 use rustc::ty::query::Providers;
 use rustc::ty::subst::SubstsRef;
 use rustc::ty::Instance;
@@ -206,6 +206,12 @@ fn exported_symbols_provider_local(
         }));
     }
 
+    if let Some(Sanitizer::Memory) = tcx.sess.opts.debugging_opts.sanitizer {
+        // Similar to profiling, preserve weak msan symbol during LTO.
+        let exported_symbol = ExportedSymbol::NoDefId(SymbolName::new("__msan_track_origins"));
+        symbols.push((exported_symbol, SymbolExportLevel::C));
+    }
+
     if tcx.sess.crate_types.borrow().contains(&config::CrateType::Dylib) {
         let symbol_name = metadata_symbol_name(tcx);
         let exported_symbol = ExportedSymbol::NoDefId(SymbolName::new(&symbol_name));

src/test/codegen/sanitizer-memory-track-orgins.rs

@@ -4,17 +4,21 @@
 // needs-sanitizer-support
 // only-linux
 // only-x86_64
-// revisions:MSAN-0 MSAN-1 MSAN-2
+// revisions:MSAN-0 MSAN-1 MSAN-2 MSAN-1-LTO MSAN-2-LTO
 //
 //[MSAN-0] compile-flags: -Zsanitizer=memory
 //[MSAN-1] compile-flags: -Zsanitizer=memory -Zsanitizer-memory-track-origins=1
 //[MSAN-2] compile-flags: -Zsanitizer=memory -Zsanitizer-memory-track-origins
+//[MSAN-1-LTO] compile-flags: -Zsanitizer=memory -Zsanitizer-memory-track-origins=1 -C lto=fat
+//[MSAN-2-LTO] compile-flags: -Zsanitizer=memory -Zsanitizer-memory-track-origins -C lto=fat
 
 #![crate_type="lib"]
 
 // MSAN-0-NOT: @__msan_track_origins
 // MSAN-1:     @__msan_track_origins = weak_odr local_unnamed_addr constant i32 1
 // MSAN-2:     @__msan_track_origins = weak_odr local_unnamed_addr constant i32 2
+// MSAN-1-LTO: @__msan_track_origins = weak_odr local_unnamed_addr constant i32 1
+// MSAN-2-LTO: @__msan_track_origins = weak_odr local_unnamed_addr constant i32 2
 //
 // MSAN-0-LABEL: define void @copy(
 // MSAN-1-LABEL: define void @copy(