MS Compat: mark globals emitted in read-only sections const

They cannot be written to, so marking them const makes sense and may improve
optimisation.

As a side-effect, SectionInfos has to be moved from Sema to ASTContext.

It also fixes this problem, that occurs when compiling ATL:

  warning LNK4254: section 'ATL' (C0000040) merged into '.rdata' (40000040) with different attributes

The ATL headers are putting variables in a special section that's marked
read-only. However, Clang currently can't model that read-onlyness in the IR.
But, by making the variables const, the section does become read-only, and
the linker warning is avoided.

Differential Revision: http://reviews.llvm.org/D5812

llvm-svn: 219960

1 files changed, 6 insertions, 4 deletions

diff --git a/clang/lib/Sema/SemaDecl.cpp b/clang/lib/Sema/SemaDecl.cpp
index 65eafd5a3c2..6f20c6a9f78 100644
--- a/clang/lib/Sema/SemaDecl.cpp
+++ b/clang/lib/Sema/SemaDecl.cpp
@@ -7334,7 +7334,9 @@ Sema::ActOnFunctionDeclarator(Scope *S, Declarator &D, DeclContext *DC,
                                     CodeSegStack.CurrentValue->getString(),
                                     CodeSegStack.CurrentPragmaLocation));
     if (UnifySection(CodeSegStack.CurrentValue->getString(),
-                     PSF_Implicit | PSF_Execute | PSF_Read, NewFD))
+                     ASTContext::PSF_Implicit | ASTContext::PSF_Execute |
+                         ASTContext::PSF_Read,
+                     NewFD))
       NewFD->dropAttr<SectionAttr>();
   }
 
@@ -9403,15 +9405,15 @@ void Sema::CheckCompleteVariableDeclaration(VarDecl *var) {
   if (var->isThisDeclarationADefinition() &&
       ActiveTemplateInstantiations.empty()) {
     PragmaStack<StringLiteral *> *Stack = nullptr;
-    int SectionFlags = PSF_Implicit | PSF_Read;
+    int SectionFlags = ASTContext::PSF_Implicit | ASTContext::PSF_Read;
     if (var->getType().isConstQualified())
       Stack = &ConstSegStack;
     else if (!var->getInit()) {
       Stack = &BSSSegStack;
-      SectionFlags |= PSF_Write;
+      SectionFlags |= ASTContext::PSF_Write;
     } else {
       Stack = &DataSegStack;
-      SectionFlags |= PSF_Write;
+      SectionFlags |= ASTContext::PSF_Write;
     }
     if (!var->hasAttr<SectionAttr>() && Stack->CurrentValue)
       var->addAttr(