[cxx-interop] Link against -lc++ on Darwin and -lstdc++ on Linux.

Author: zoecarver

lib/IRGen/GenDecl.cpp

@@ -469,10 +469,14 @@ void IRGenModule::emitSourceFile(SourceFile &SF) {
   if (ObjCInterop)
     this->addLinkLibrary(LinkLibrary("objc", LibraryKind::Library));
 
-  // Automatically with libc++ when possible.
-  if (Context.LangOpts.EnableCXXInterop && Context.LangOpts.Target.isOSDarwin())
-    this->addLinkLibrary(LinkLibrary("c++", LibraryKind::Library));
-  
+  // If C++ interop is enabled, add -lc++ on Darwin and -lstdc++ on linux.
+  if (Context.LangOpts.EnableCXXInterop) {
+    if (Context.LangOpts.Target.isOSDarwin())
+      this->addLinkLibrary(LinkLibrary("c++", LibraryKind::Library));
+    else if (Context.LangOpts.Target.isOSLinux())
+      this->addLinkLibrary(LinkLibrary("stdc++", LibraryKind::Library));
+  }
+
   // FIXME: It'd be better to have the driver invocation or build system that
   // executes the linker introduce these compatibility libraries, since at
   // that point we know whether we're building an executable, which is the only