From: Nico Weber <nicolasweber@gmx.de>
Date: Wed, 15 Apr 2015 23:04:24 +0000 (+0000)
Subject: Don't crash when a selectany symbol would get common linkage
X-Git-Url: https://granicus.if.org/sourcecode?a=commitdiff_plain;h=7bbbb59b401ea3cbd653e0c7cc042e0a8bf7f1d3;p=clang

Don't crash when a selectany symbol would get common linkage

Things can't both be in comdats and have common linkage, so never give things
in comdats common linkage. Common linkage is only used in .c files, and the
only thing that can trigger a comdat in c is selectany from what I can tell.
Fixes PR23243.

Also address an over-the-shoulder review comment from rnk by moving the
hasAttr<SelectAnyAttr>() in Decl.cpp around a bit. It only makes a minor
difference for selectany on global variables, so it goes well with the rest of
this patch.

http://reviews.llvm.org/D9042


git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@235053 91177308-0d34-0410-b5e6-96231b3b80d8
---

diff --git a/lib/AST/Decl.cpp b/lib/AST/Decl.cpp
index 1cdc24e65f..628c9b053e 100644
--- a/lib/AST/Decl.cpp
+++ b/lib/AST/Decl.cpp
@@ -1915,7 +1915,7 @@ VarDecl::isThisDeclarationADefinition(ASTContext &C) const {
   if (hasInit())
     return Definition;
 
-  if (hasAttr<AliasAttr>())
+  if (hasAttr<AliasAttr>() || hasAttr<SelectAnyAttr>())
     return Definition;
 
   // A variable template specialization (other than a static data member
@@ -1925,14 +1925,14 @@ VarDecl::isThisDeclarationADefinition(ASTContext &C) const {
       getTemplateSpecializationKind() != TSK_ExplicitSpecialization)
     return DeclarationOnly;
 
-  if (!hasAttr<SelectAnyAttr>() && hasExternalStorage())
+  if (hasExternalStorage())
     return DeclarationOnly;
 
   // [dcl.link] p7:
   //   A declaration directly contained in a linkage-specification is treated
   //   as if it contains the extern specifier for the purpose of determining
   //   the linkage of the declared name and whether it is a definition.
-  if (!hasAttr<SelectAnyAttr>() && isSingleLineLanguageLinkage(*this))
+  if (isSingleLineLanguageLinkage(*this))
     return DeclarationOnly;
 
   // C99 6.9.2p2:
diff --git a/lib/CodeGen/CodeGenModule.cpp b/lib/CodeGen/CodeGenModule.cpp
index f60a68ab01..17b7ddc768 100644
--- a/lib/CodeGen/CodeGenModule.cpp
+++ b/lib/CodeGen/CodeGenModule.cpp
@@ -2134,7 +2134,8 @@ void CodeGenModule::EmitGlobalVarDefinition(const VarDecl *D) {
 }
 
 static bool isVarDeclStrongDefinition(const ASTContext &Context,
-                                      const VarDecl *D, bool NoCommon) {
+                                      CodeGenModule &CGM, const VarDecl *D,
+                                      bool NoCommon) {
   // Don't give variables common linkage if -fno-common was specified unless it
   // was overridden by a NoCommon attribute.
   if ((NoCommon || D->hasAttr<NoCommonAttr>()) && !D->hasAttr<CommonAttr>())
@@ -2159,6 +2160,10 @@ static bool isVarDeclStrongDefinition(const ASTContext &Context,
   if (D->hasAttr<WeakImportAttr>())
     return true;
 
+  // A variable cannot be both common and exist in a comdat.
+  if (shouldBeInCOMDAT(CGM, *D))
+    return true;
+
   // Declarations with a required alignment do not have common linakge in MSVC
   // mode.
   if (Context.getLangOpts().MSVCCompat) {
@@ -2227,7 +2232,7 @@ llvm::GlobalValue::LinkageTypes CodeGenModule::getLLVMLinkageForDeclarator(
   // C++ doesn't have tentative definitions and thus cannot have common
   // linkage.
   if (!getLangOpts().CPlusPlus && isa<VarDecl>(D) &&
-      !isVarDeclStrongDefinition(Context, cast<VarDecl>(D),
+      !isVarDeclStrongDefinition(Context, *this, cast<VarDecl>(D),
                                  CodeGenOpts.NoCommon))
     return llvm::GlobalVariable::CommonLinkage;
 
diff --git a/test/CodeGen/ms-declspecs.c b/test/CodeGen/ms-declspecs.c
index 985c227faa..c32733e65f 100644
--- a/test/CodeGen/ms-declspecs.c
+++ b/test/CodeGen/ms-declspecs.c
@@ -6,8 +6,10 @@ const __declspec(selectany) int x2 = 2;
 // CHECK: @x2 = weak_odr constant i32 2, comdat, align 4
 
 // selectany turns extern variable declarations into definitions.
-extern __declspec(selectany) int x3;
+__declspec(selectany) int x3;
+extern __declspec(selectany) int x4;
 // CHECK: @x3 = weak_odr global i32 0, comdat, align 4
+// CHECK: @x4 = weak_odr global i32 0, comdat, align 4
 
 struct __declspec(align(16)) S {
   char x;
diff --git a/test/CodeGen/ms-declspecs.cpp b/test/CodeGen/ms-declspecs.cpp
index f77c7cb891..decf5d6fcb 100644
--- a/test/CodeGen/ms-declspecs.cpp
+++ b/test/CodeGen/ms-declspecs.cpp
@@ -7,7 +7,9 @@ extern "C++" __declspec(selectany) int x3;
 extern "C" {
 __declspec(selectany) int x4;
 }
+__declspec(selectany) int x5;
 // CHECK: @"\01?x1@@3HA" = weak_odr global i32 0, comdat, align 4
 // CHECK: @x2 = weak_odr global i32 0, comdat, align 4
 // CHECK: @"\01?x3@@3HA"  = weak_odr global i32 0, comdat, align 4
 // CHECK: @x4 = weak_odr global i32 0, comdat, align 4
+// CHECK: @"\01?x5@@3HA"  = weak_odr global i32 0, comdat, align 4