From 195d8ef452a0712105a88194848db736d415f3c2 Mon Sep 17 00:00:00 2001
From: Richard Smith <richard-llvm@metafoo.co.uk>
Date: Thu, 29 May 2014 03:15:31 +0000
Subject: When merging functions across modules (and in particular,
 instantiations of member functions), ensure that the redecl chain never
 transitions from 'inline' to 'not inline', since that violates an AST
 invariant.

llvm-svn: 209794
---
 clang/lib/Serialization/ASTReaderDecl.cpp | 39 +++++++++++++++++++++++++++++--
 1 file changed, 37 insertions(+), 2 deletions(-)

(limited to 'clang/lib/Serialization/ASTReaderDecl.cpp')

diff --git a/clang/lib/Serialization/ASTReaderDecl.cpp b/clang/lib/Serialization/ASTReaderDecl.cpp
index 8a0849cb909..7e652c47181 100644
--- a/clang/lib/Serialization/ASTReaderDecl.cpp
+++ b/clang/lib/Serialization/ASTReaderDecl.cpp
@@ -2491,6 +2491,32 @@ void ASTDeclReader::attachPreviousDecl(Decl *D, Decl *Previous) {
   D->IdentifierNamespace |=
       Previous->IdentifierNamespace &
       (Decl::IDNS_Ordinary | Decl::IDNS_Tag | Decl::IDNS_Type);
+
+  // If the previous declaration is an inline function declaration, then this
+  // declaration is too.
+  if (auto *FD = dyn_cast<FunctionDecl>(D)) {
+    if (cast<FunctionDecl>(Previous)->IsInline != FD->IsInline) {
+      // FIXME: [dcl.fct.spec]p4:
+      //   If a function with external linkage is declared inline in one
+      //   translation unit, it shall be declared inline in all translation
+      //   units in which it appears.
+      //
+      // Be careful of this case:
+      //
+      // module A:
+      //   template<typename T> struct X { void f(); };
+      //   template<typename T> inline void X<T>::f() {}
+      //
+      // module B instantiates the declaration of X<int>::f
+      // module C instantiates the definition of X<int>::f
+      //
+      // If module B and C are merged, we do not have a violation of this rule.
+      //
+      //if (!FD->IsInline || Previous->getOwningModule())
+      //  Diag(FD->getLocation(), diag::err_odr_differing_inline);
+      FD->IsInline = true;
+    }
+  }
 }
 
 template<typename DeclT>
@@ -3162,8 +3188,17 @@ void ASTDeclReader::UpdateDecl(Decl *D, ModuleFile &ModuleFile,
         return;
       }
 
-      if (Record[Idx++])
-        FD->setImplicitlyInline();
+      if (Record[Idx++]) {
+        // Maintain AST consistency: any later redeclarations of this function
+        // are inline if this one is. (We might have merged another declaration
+        // into this one.)
+        for (auto *D = FD->getMostRecentDecl(); /**/;
+             D = D->getPreviousDecl()) {
+          D->setImplicitlyInline();
+          if (D == FD)
+            break;
+        }
+      }
       FD->setInnerLocStart(Reader.ReadSourceLocation(ModuleFile, Record, Idx));
       if (auto *CD = dyn_cast<CXXConstructorDecl>(FD))
         std::tie(CD->CtorInitializers, CD->NumCtorInitializers) =
-- 
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