Revert r240335.

This failed to solve the problem it was aimed at, and introduced just as many
issues as it resolved. Realistically, we need to deal with the possibility that
multiple modules might define different internal linkage symbols with the same
name, and this isn't a problem unless two such symbols are simultaneously
visible.

The case where two modules define equivalent internal linkage symbols is
handled by r252063: if lookup finds multiple sufficiently-similar entities from
different modules, we just pick one of them as an extension (but we keep them
separate).

llvm-svn: 252957

7 files changed, 7 insertions, 14 deletions

diff --git a/clang/include/clang/Basic/LangOptions.def b/clang/include/clang/Basic/LangOptions.def
index 75816e9a267..fdf7e49499b 100644
--- a/clang/include/clang/Basic/LangOptions.def
+++ b/clang/include/clang/Basic/LangOptions.def
@@ -133,7 +133,6 @@ COMPATIBLE_LANGOPT(ModulesStrictDeclUse, 1, 0, "require declaration of module us
 BENIGN_LANGOPT(ModulesErrorRecovery, 1, 1, "automatically import modules as needed when performing error recovery")
 BENIGN_LANGOPT(ImplicitModules, 1, 1, "build modules that are not specified via -fmodule-file")
 COMPATIBLE_LANGOPT(ModulesLocalVisibility, 1, 0, "local submodule visibility")
-COMPATIBLE_LANGOPT(ModulesHideInternalLinkage, 1, 1, "hiding non-visible internal linkage declarations from redeclaration lookup")
 COMPATIBLE_LANGOPT(Optimize          , 1, 0, "__OPTIMIZE__ predefined macro")
 COMPATIBLE_LANGOPT(OptimizeSize      , 1, 0, "__OPTIMIZE_SIZE__ predefined macro")
 LANGOPT(Static            , 1, 0, "__STATIC__ predefined macro (as opposed to __DYNAMIC__)")
diff --git a/clang/include/clang/Driver/CC1Options.td b/clang/include/clang/Driver/CC1Options.td
index 24d32eea90d..56caea85b17 100644
--- a/clang/include/clang/Driver/CC1Options.td
+++ b/clang/include/clang/Driver/CC1Options.td
@@ -388,10 +388,6 @@ def fmodules_local_submodule_visibility :
 def fmodule_format_EQ : Joined<["-"], "fmodule-format=">,
   HelpText<"Select the container format for clang modules and PCH. "
            "Supported options are 'raw' and 'obj'.">;
-def fno_modules_hide_internal_linkage :
-  Flag<["-"], "fno-modules-hide-internal-linkage">,
-  HelpText<"Make all declarations visible to redeclaration lookup, "
-           "even if they have internal linkage.">;
 def ftest_module_file_extension_EQ :
   Joined<["-"], "ftest-module-file-extension=">,
   HelpText<"introduce a module file extension for testing purposes. "
diff --git a/clang/include/clang/Sema/Sema.h b/clang/include/clang/Sema/Sema.h
index c6506e44e30..469c181f105 100644
--- a/clang/include/clang/Sema/Sema.h
+++ b/clang/include/clang/Sema/Sema.h
@@ -277,9 +277,7 @@ class Sema {
     // it will keep having external linkage. If it has internal linkage, we
     // will not link it. Since it has no previous decls, it will remain
     // with internal linkage.
-    if (getLangOpts().ModulesHideInternalLinkage)
-      return isVisible(Old) || New->isExternallyVisible();
-    return true;
+    return isVisible(Old) || New->isExternallyVisible();
   }
 
 public:
diff --git a/clang/lib/Frontend/CompilerInvocation.cpp b/clang/lib/Frontend/CompilerInvocation.cpp
index 7f401aa9257..91917cf5100 100644
--- a/clang/lib/Frontend/CompilerInvocation.cpp
+++ b/clang/lib/Frontend/CompilerInvocation.cpp
@@ -1627,8 +1627,6 @@ static void ParseLangArgs(LangOptions &Opts, ArgList &Args, InputKind IK,
       Args.hasArg(OPT_fmodules_decluse) || Opts.ModulesStrictDeclUse;
   Opts.ModulesLocalVisibility =
       Args.hasArg(OPT_fmodules_local_submodule_visibility);
-  Opts.ModulesHideInternalLinkage =
-      !Args.hasArg(OPT_fno_modules_hide_internal_linkage);
   Opts.ModulesSearchAll = Opts.Modules &&
     !Args.hasArg(OPT_fno_modules_search_all) &&
     Args.hasArg(OPT_fmodules_search_all);
diff --git a/clang/lib/Sema/SemaDecl.cpp b/clang/lib/Sema/SemaDecl.cpp
index 172952e8ca1..728697e78f5 100644
--- a/clang/lib/Sema/SemaDecl.cpp
+++ b/clang/lib/Sema/SemaDecl.cpp
@@ -4822,7 +4822,6 @@ NamedDecl *Sema::HandleDeclarator(Scope *S, Declarator &D,
   // If we're hiding internal-linkage symbols in modules from redeclaration
   // lookup, let name lookup know.
   if ((getLangOpts().Modules || getLangOpts().ModulesLocalVisibility) &&
-      getLangOpts().ModulesHideInternalLinkage &&
       D.getDeclSpec().getStorageClassSpec() != DeclSpec::SCS_typedef)
     Previous.setAllowHiddenInternal(false);
 
diff --git a/clang/test/Modules/submodules-merge-defs.cpp b/clang/test/Modules/submodules-merge-defs.cpp
index 6a46e6dfa8a..bb8e69367ca 100644
--- a/clang/test/Modules/submodules-merge-defs.cpp
+++ b/clang/test/Modules/submodules-merge-defs.cpp
@@ -3,7 +3,7 @@
 // RUN: %clang_cc1 -x c++ -std=c++11 -fmodules-cache-path=%t -fmodules -fimplicit-module-maps -I %S/Inputs/submodules-merge-defs %s -verify -fno-modules-error-recovery
 // RUN: %clang_cc1 -x c++ -std=c++11 -fmodules-cache-path=%t -fmodules -fimplicit-module-maps -I %S/Inputs/submodules-merge-defs %s -verify -fno-modules-error-recovery -fmodules-local-submodule-visibility -DTEXTUAL
 // RUN: %clang_cc1 -x c++ -std=c++11 -fmodules-cache-path=%t -fmodules -fimplicit-module-maps -I %S/Inputs/submodules-merge-defs %s -verify -fno-modules-error-recovery -fmodules-local-submodule-visibility
-// RUN: %clang_cc1 -x c++ -std=c++11 -fmodules-cache-path=%t -fimplicit-module-maps -I %S/Inputs/submodules-merge-defs %s -verify -fno-modules-error-recovery -fmodules-local-submodule-visibility -DTEXTUAL -DEARLY_INDIRECT_INCLUDE -fno-modules-hide-internal-linkage
+// RUN: %clang_cc1 -x c++ -std=c++11 -fmodules-cache-path=%t -fimplicit-module-maps -I %S/Inputs/submodules-merge-defs %s -verify -fno-modules-error-recovery -fmodules-local-submodule-visibility -DTEXTUAL -DEARLY_INDIRECT_INCLUDE
 // RUN: %clang_cc1 -x c++ -std=c++11 -fmodules-cache-path=%t -fmodules -fimplicit-module-maps -I %S/Inputs/submodules-merge-defs %s -verify -fno-modules-error-recovery -fmodules-local-submodule-visibility -fmodule-feature use_defs_twice -DIMPORT_USE_2
 
 // Trigger import of definitions, but don't make them visible.
@@ -111,4 +111,9 @@ MergeFunctionTemplateSpecializations::X<int>::Q<char> xiqc;
 #ifdef TEXTUAL
 #include "use-defs.h"
 void use_static_inline() { StaticInline::g({}); }
+#ifdef EARLY_INDIRECT_INCLUDE
+// expected-warning@-2 {{ambiguous use of internal linkage declaration 'g' defined in multiple modules}}
+// expected-note@defs.h:71 {{declared here in module 'redef'}}
+// expected-note@defs.h:71 {{declared here in module 'stuff.use'}}
+#endif
 #endif
diff --git a/clang/test/Modules/using-decl.cpp b/clang/test/Modules/using-decl.cpp
index 1677585ddaf..b24593b5780 100644
--- a/clang/test/Modules/using-decl.cpp
+++ b/clang/test/Modules/using-decl.cpp
@@ -1,8 +1,6 @@
 // RUN: rm -rf %t
 // RUN: %clang_cc1 -x objective-c++ -std=c++11 -fmodules -fimplicit-module-maps -fmodules-cache-path=%t -I %S/Inputs %s -verify -DEARLY_IMPORT
 // RUN: %clang_cc1 -x objective-c++ -std=c++11 -fmodules -fimplicit-module-maps -fmodules-cache-path=%t -I %S/Inputs %s -verify -UEARLY_IMPORT
-// RUN: %clang_cc1 -x objective-c++ -std=c++11 -fmodules -fimplicit-module-maps -fmodules-cache-path=%t -I %S/Inputs %s -verify -DEARLY_IMPORT -fno-modules-hide-internal-linkage
-// RUN: %clang_cc1 -x objective-c++ -std=c++11 -fmodules -fimplicit-module-maps -fmodules-cache-path=%t -I %S/Inputs %s -verify -UEARLY_IMPORT -fno-modules-hide-internal-linkage
 // RUN: %clang_cc1 -x objective-c++ -std=c++11 -fmodules -fimplicit-module-maps -fmodules-cache-path=%t -I %S/Inputs %s -verify -DEARLY_IMPORT -fmodules-local-submodule-visibility
 // RUN: %clang_cc1 -x objective-c++ -std=c++11 -fmodules -fimplicit-module-maps -fmodules-cache-path=%t -I %S/Inputs %s -verify -UEARLY_IMPORT -fmodules-local-submodule-visibility