[modules] Add a flag to disable the feature that permits conflicting redefinitions...

Such conflicts are an accident waiting to happen, and this feature conflicts
with the desire to include existing headers into multiple modules and merge the
results. (In an ideal world, it should not be possible to export internal
linkage symbols from a module, but sadly the glibc and libstdc++ headers
provide 'static inline' functions in a few cases.)

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@240335 91177308-0d34-0410-b5e6-96231b3b80d8

diff --git a/include/clang/Basic/LangOptions.def b/include/clang/Basic/LangOptions.def
index bef122f093c41bc2b3994ce7c4ace0c04984a42b..b27605b15d28fc8c231808e4dc7d92fb4f7dc2b6 100644 (file)
--- a/include/clang/Basic/LangOptions.def
+++ b/include/clang/Basic/LangOptions.def
@@ -130,6 +130,7 @@ 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/include/clang/Driver/CC1Options.td b/include/clang/Driver/CC1Options.td
index f2ef71e2f9199628dc370ef889e8259498613884..60cc6ec11568643fcad6682e7d169f223e70c915 100644 (file)
--- a/include/clang/Driver/CC1Options.td
+++ b/include/clang/Driver/CC1Options.td
@@ -369,6 +369,10 @@ def fmodules_local_submodule_visibility :
   Flag<["-"], "fmodules-local-submodule-visibility">,
   HelpText<"Enforce name visibility rules across submodules of the same "
            "top-level module.">;
+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 fconcepts_ts : Flag<["-"], "fconcepts-ts">,
   HelpText<"Enable C++ Extensions for Concepts.">;
 

diff --git a/include/clang/Sema/Sema.h b/include/clang/Sema/Sema.h
index 4d815262592ea951d763e5edffd8567c3400d7ef..df5182b52f4bdac2bf005119b633dc651cc936e6 100644 (file)
--- a/include/clang/Sema/Sema.h
+++ b/include/clang/Sema/Sema.h
@@ -277,7 +277,9 @@ 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.
-    return isVisible(Old) || New->isExternallyVisible();
+    if (getLangOpts().ModulesHideInternalLinkage)
+      return isVisible(Old) || New->isExternallyVisible();
+    return true;
   }
 
 public:

diff --git a/lib/Frontend/CompilerInvocation.cpp b/lib/Frontend/CompilerInvocation.cpp
index 7a3391685a472b0aaf0a0c6ec6c7e34609179097..2d26548db3957e2169fa97f47cc734c88bfa3ef9 100644 (file)
--- a/lib/Frontend/CompilerInvocation.cpp
+++ b/lib/Frontend/CompilerInvocation.cpp
@@ -1521,6 +1521,8 @@ 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/lib/Sema/SemaDecl.cpp b/lib/Sema/SemaDecl.cpp
index cb1be8d505360f67ebbfb9c181f1abb6308b36f5..ee03994058581785baafabc98a96de1d2e6c7340 100644 (file)
--- a/lib/Sema/SemaDecl.cpp
+++ b/lib/Sema/SemaDecl.cpp
@@ -1804,7 +1804,8 @@ static void filterNonConflictingPreviousDecls(Sema &S,
                                               NamedDecl *decl,
                                               LookupResult &previous){
   // This is only interesting when modules are enabled.
-  if (!S.getLangOpts().Modules && !S.getLangOpts().ModulesLocalVisibility)
+  if ((!S.getLangOpts().Modules && !S.getLangOpts().ModulesLocalVisibility) ||
+      !S.getLangOpts().ModulesHideInternalLinkage)
     return;
 
   // Empty sets are uninteresting.
@@ -3453,8 +3454,9 @@ void Sema::MergeVarDecl(VarDecl *New, LookupResult &Previous) {
       New->isThisDeclarationADefinition() == VarDecl::Definition &&
       (Def = Old->getDefinition())) {
     NamedDecl *Hidden = nullptr;
-    if (!hasVisibleDefinition(Def, &Hidden) && 
-        (New->getDescribedVarTemplate() ||
+    if (!hasVisibleDefinition(Def, &Hidden) &&
+        (New->getFormalLinkage() == InternalLinkage ||
+         New->getDescribedVarTemplate() ||
          New->getNumTemplateParameterLists() ||
          New->getDeclContext()->isDependentContext())) {
       // The previous definition is hidden, and multiple definitions are
@@ -8946,7 +8948,8 @@ void Sema::AddInitializerToDecl(Decl *RealDecl, Expr *Init,
   if ((Def = VDecl->getDefinition()) && Def != VDecl) {
     NamedDecl *Hidden = nullptr;
     if (!hasVisibleDefinition(Def, &Hidden) && 
-        (VDecl->getDescribedVarTemplate() ||
+        (VDecl->getFormalLinkage() == InternalLinkage ||
+         VDecl->getDescribedVarTemplate() ||
          VDecl->getNumTemplateParameterLists() ||
          VDecl->getDeclContext()->isDependentContext())) {
       // The previous definition is hidden, and multiple definitions are
@@ -10367,7 +10370,8 @@ Sema::CheckForFunctionRedefinition(FunctionDecl *FD,
   // in this case? That may be necessary for functions that return local types
   // through a deduced return type, or instantiate templates with local types.
   if (!hasVisibleDefinition(Definition) &&
-      (Definition->isInlineSpecified() ||
+      (Definition->getFormalLinkage() == InternalLinkage ||
+       Definition->isInlineSpecified() ||
        Definition->getDescribedFunctionTemplate() ||
        Definition->getNumTemplateParameterLists()))
     return;

diff --git a/test/Modules/submodules-merge-defs.cpp b/test/Modules/submodules-merge-defs.cpp
index 94c0fd354c98b94fb149c5f0159f9ae6ff0b31df..6f2754be4622e713f21596dd044cdfc7cdabe75a 100644 (file)
--- a/test/Modules/submodules-merge-defs.cpp
+++ b/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
+// 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 -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.
@@ -92,3 +92,8 @@ template<typename T, int N, template<typename> class K> struct J;
 J<> post_j2;
 FriendDefArg::Y<int> friend_def_arg;
 FriendDefArg::D<> friend_def_arg_d;
+
+#ifdef TEXTUAL
+#include "use-defs.h"
+void use_static_inline() { StaticInline::g({}); }
+#endif