[PATCH] D158538: [MS-ABI] Remove comdat attribute for inheriting ctor.

[Jennifer Yu via Phabricator via cfe-commits]

jyu2 created this revision.
jyu2 added reviewers: rnk, rsmith, majnemer, cfe-commits.
jyu2 added a project: clang.
Herald added a project: All.
jyu2 requested review of this revision.

Currently, for MS, the linkage for the inheriting constructors is set to
internal.  However, the comdat attribute is also set like:

define internal noundef ptr @"??0?$B at _N@@qeaa at AEBVF@@aebua@@@z"(ptr noundef nonnull returned align 1 dereferenceable(1) %this, ptr noundef nonnull align 1 dereferenceable(1) %0, ptr noundef nonnull align 1 dereferenceable(1) %1) unnamed_addr comdat

This could cause linker to fail.

The change is to remove comdat attribute for the inheriting constructor
to make linker happy.


Repository:
  rG LLVM Github Monorepo

https://reviews.llvm.org/D158538

Files:
  clang/lib/AST/ASTContext.cpp
  clang/test/CodeGenCXX/ms-inheriting-ctor.cpp


Index: clang/test/CodeGenCXX/ms-inheriting-ctor.cpp
===================================================================
--- /dev/null
+++ clang/test/CodeGenCXX/ms-inheriting-ctor.cpp
@@ -0,0 +1,42 @@
+// RUN: %clang_cc1 -fcxx-exceptions -triple=x86_64-windows-msvc -emit-llvm %s -o - | FileCheck %s
+
+class F {
+public:
+  F(wchar_t *);
+};
+using a = F;
+struct A {};
+struct b {
+  b(a, F, A);
+};
+template <typename, typename> struct c : b {
+  c(const a &p1, const A &d) : b(p1, 0, d) {}
+};
+template <typename e> struct B : c<e, b> {
+  using c<e, b>::c;
+};
+class f {
+public:
+  f(...);
+}
+
+typedef g;
+class C {
+public:
+  C(g, f);
+};
+static wchar_t h;
+class D {
+public:
+  static C E();
+};
+
+C D::E() {
+  C i(B<bool>(&h, {}), f());
+  return i;
+}
+
+// Inheriting ctor has internal linkage, should not with comdat.
+
+// CHECK-LABEL: define internal noundef ptr @"??0?$B at _N@@QEAA at AEBVF@@AEBUA@@@Z"(ptr noundef nonnull returned align 1 dereferenceable(1) %this, ptr noundef nonnull align 1 dereferenceable(1) %0, ptr noundef nonnull align 1 dereferenceable(1) %1) unnamed_addr #2 align 2
+// CHECK-LABEL: define linkonce_odr dso_local noundef ptr @"??0?$c at _NUb@@@@QEAA at AEBVF@@AEBUA@@@Z"(ptr noundef nonnull returned align 1 dereferenceable(1) %this, ptr noundef nonnull align 1 dereferenceable(1) %p1, ptr noundef nonnull align 1 dereferenceable(1) %d) unnamed_addr #2 comdat align 2
Index: clang/lib/AST/ASTContext.cpp
===================================================================
--- clang/lib/AST/ASTContext.cpp
+++ clang/lib/AST/ASTContext.cpp
@@ -11688,6 +11688,14 @@
   if (FD->isMSExternInline())
     return GVA_StrongODR;
 
+  if (Context.getTargetInfo().getCXXABI().isMicrosoft() &&
+      isa<CXXConstructorDecl>(FD) &&
+      cast<CXXConstructorDecl>(FD)->isInheritingConstructor())
+    // Our approach to inheriting constructors is fundamentally different from
+    // that used by the MS ABI, so keep our inheriting constructor thunks
+    // internal rather than trying to pick an unambiguous mangling for them.
+    return GVA_Internal;
+
   return GVA_DiscardableODR;
 }
 


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