[PATCH] D133266: [MinGW] Reject explicit non-default visibility applied to dllexport/dllimport declaration

[Fangrui Song via Phabricator via cfe-commits]

MaskRay created this revision.
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dllimport/dllexport is incompatible with protected/hidden visibilities.
(Arguably dllexport is compatible with protected but we can reject it
for simplicity.)

When an explicit visibility attribute applies on a dllexport/dllimport
declaration, report a Frontend error (Sema does not compute visibility).


Repository:
  rG LLVM Github Monorepo

https://reviews.llvm.org/D133266

Files:
  clang/include/clang/Basic/DiagnosticFrontendKinds.td
  clang/lib/CodeGen/CodeGenModule.cpp
  clang/test/CodeGenCXX/dllstorage-visibility.cpp


Index: clang/test/CodeGenCXX/dllstorage-visibility.cpp
===================================================================
--- clang/test/CodeGenCXX/dllstorage-visibility.cpp
+++ clang/test/CodeGenCXX/dllstorage-visibility.cpp
@@ -4,10 +4,18 @@
 // RUN: %clang_cc1 -emit-llvm -triple x86_64-windows-gnu -fdeclspec -fvisibility-inlines-hidden -o - %s | FileCheck %s --check-prefix=GNU
 // RUN: %clang_cc1 -emit-llvm -triple x86_64-windows-gnu -fdeclspec -fvisibility=hidden -o - %s | FileCheck %s --check-prefix=GNU
 
+// RUN: %clang_cc1 -emit-llvm-only -verify -triple x86_64-windows-gnu -fdeclspec -DERR1 -o - %s
+// RUN: %clang_cc1 -emit-llvm-only -verify -triple x86_64-windows-gnu -fdeclspec -fvisibility=hidden -DERR1 -o - %s
+// RUN: %clang_cc1 -emit-llvm-only -verify -triple x86_64-windows-gnu -fdeclspec -DERR2 -o - %s
+
 #define CONCAT2(x, y) x##y
 #define CONCAT(x, y) CONCAT2(x, y)
 #define USE(func) void CONCAT(use, __LINE__)() { func(); }
 
+#define HIDDEN __attribute__((visibility("hidden")))
+#define PROTECTED __attribute__((visibility("protected")))
+#define DEFAULT __attribute__((visibility("default")))
+
 // MSVC-DAG: declare dllimport void @"?bar at foo@@QEAAXXZ"(
 // GNU-DAG: define linkonce_odr hidden void @_ZN3foo3barEv(
 
@@ -24,3 +32,17 @@
 // GNU-DAG: define weak_odr dso_local dllexport void @_Z15exported_inlinev(
 __declspec(dllexport) inline void exported_inline() {}
 USE(exported_inline)
+
+#if defined(ERR1)
+// expected-error at +1 {{non-default visibility cannot be applied to 'dllimport' declaration}}
+__attribute__((dllimport)) HIDDEN void imported_hidden();
+
+__attribute__((dllexport)) DEFAULT void exported_default() {}
+// expected-error at +1 {{non-default visibility cannot be applied to 'dllexport' declaration}}
+__attribute__((dllexport)) HIDDEN void exported_hidden() { imported_hidden(); }
+#elif defined(ERR2)
+struct PROTECTED C {
+  // expected-error at +1 {{non-default visibility cannot be applied to 'dllexport' declaration}}
+  __attribute__((dllexport)) void exported_protected() {}
+};
+#endif
Index: clang/lib/CodeGen/CodeGenModule.cpp
===================================================================
--- clang/lib/CodeGen/CodeGenModule.cpp
+++ clang/lib/CodeGen/CodeGenModule.cpp
@@ -1099,8 +1099,6 @@
 
 void CodeGenModule::setGlobalVisibility(llvm::GlobalValue *GV,
                                         const NamedDecl *D) const {
-  if (GV->hasDLLExportStorageClass() || GV->hasDLLImportStorageClass())
-    return;
   // Internal definitions always have default visibility.
   if (GV->hasLocalLinkage()) {
     GV->setVisibility(llvm::GlobalValue::DefaultVisibility);
@@ -1111,6 +1109,14 @@
   // Set visibility for definitions, and for declarations if requested globally
   // or set explicitly.
   LinkageInfo LV = D->getLinkageAndVisibility();
+  if (GV->hasDLLExportStorageClass() || GV->hasDLLImportStorageClass()) {
+    // Reject explicit non-default visibility on dllexport/dllimport.
+    if (LV.isVisibilityExplicit() && LV.getVisibility() != DefaultVisibility)
+      getDiags().Report(D->getLocation(),
+                        diag::err_non_default_visibility_dllstorage)
+          << (GV->hasDLLExportStorageClass() ? "dllexport" : "dllimport");
+    return;
+  }
   if (LV.isVisibilityExplicit() || getLangOpts().SetVisibilityForExternDecls ||
       !GV->isDeclarationForLinker())
     GV->setVisibility(GetLLVMVisibility(LV.getVisibility()));
Index: clang/include/clang/Basic/DiagnosticFrontendKinds.td
===================================================================
--- clang/include/clang/Basic/DiagnosticFrontendKinds.td
+++ clang/include/clang/Basic/DiagnosticFrontendKinds.td
@@ -282,6 +282,8 @@
   "definition with same mangled name '%0' as another definition">;
 def err_cyclic_alias : Error<
   "%select{alias|ifunc}0 definition is part of a cycle">;
+def err_non_default_visibility_dllstorage : Error<
+  "non-default visibility cannot be applied to '%0' declaration">;
 def err_ifunc_resolver_return : Error<
   "ifunc resolver function must return a pointer">;
 


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