From cfe833be882f600206f1587f157b025b368497d7 Mon Sep 17 00:00:00 2001
From: Douglas Gregor <dgregor@apple.com>
Date: Mon, 17 May 2010 17:57:54 +0000
Subject: [PATCH] Diagnose a redefinition error when there are two
 instantiations of friend functions defined inside a class template. Fixes
 PR6952, the last Boost.Units failure.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@103952 91177308-0d34-0410-b5e6-96231b3b80d8
---
 lib/Sema/SemaTemplateInstantiateDecl.cpp    | 30 ++++++++++++++++++++-
 test/CXX/temp/temp.decls/temp.friend/p4.cpp | 22 +++++++++++----
 2 files changed, 46 insertions(+), 6 deletions(-)

diff --git a/lib/Sema/SemaTemplateInstantiateDecl.cpp b/lib/Sema/SemaTemplateInstantiateDecl.cpp
index 31284071ff..1280c0cb88 100644
--- a/lib/Sema/SemaTemplateInstantiateDecl.cpp
+++ b/lib/Sema/SemaTemplateInstantiateDecl.cpp
@@ -2000,7 +2000,8 @@ void Sema::InstantiateFunctionDefinition(SourceLocation PointOfInstantiation,
       Diag(Function->getLocation(), diag::err_redefinition) 
         << Function->getDeclName();
       Diag(Definition->getLocation(), diag::note_previous_definition);
-    }
+      Function->setInvalidDecl();
+    }    
     
     // We have an explicit instantiation (which already occurred) and an
     // implicit instantiation. Return without complaint.
@@ -2027,11 +2028,38 @@ void Sema::InstantiateFunctionDefinition(SourceLocation PointOfInstantiation,
       if (PatternDecl)
         Diag(PatternDecl->getLocation(), 
              diag::note_explicit_instantiation_here);
+      Function->setInvalidDecl();
     }
       
     return;
   }
 
+  // If this is an instantiation of friend function defined within a class
+  // template or class template specialization or member class thereof, 
+  // determine whether there were multiple instantiations of its lexical class.
+  if (PatternDecl->getFriendObjectKind() != Decl::FOK_None) {
+    for (FunctionDecl::redecl_iterator R = Function->redecls_begin(),
+                                    REnd = Function->redecls_end();
+         R != REnd; ++R) {
+      if (*R != Function && 
+          ((*R)->getFriendObjectKind() != Decl::FOK_None)) {
+        if (const FunctionDecl *RPattern
+                                    = (*R)->getTemplateInstantiationPattern())
+          if (RPattern->getBody(RPattern)) {
+            InstantiatingTemplate Inst(*this, PointOfInstantiation, Function);
+            if (Inst)
+              return;  
+            
+            Diag(Function->getLocation(), diag::err_redefinition) 
+              << Function->getDeclName();
+            Diag((*R)->getLocation(), diag::note_previous_definition);
+            Function->setInvalidDecl();
+            return;
+          }
+      }
+    }
+  }
+  
   // C++0x [temp.explicit]p9:
   //   Except for inline functions, other explicit instantiation declarations
   //   have the effect of suppressing the implicit instantiation of the entity
diff --git a/test/CXX/temp/temp.decls/temp.friend/p4.cpp b/test/CXX/temp/temp.decls/temp.friend/p4.cpp
index a1d7c6933f..e408720833 100644
--- a/test/CXX/temp/temp.decls/temp.friend/p4.cpp
+++ b/test/CXX/temp/temp.decls/temp.friend/p4.cpp
@@ -21,20 +21,32 @@ struct X1 {
   friend void f3(T) { } // expected-error{{redefinition of}}
   friend void f4(T) { } // expected-error{{redefinition of}}
   friend void f5(T) { } // expected-error{{redefinition of}}
-
-  // FIXME: should have a redefinition error for f6(int)
-  friend void f6(int) { }
+  friend void f6(int) { } // expected-error{{redefinition of}} \
+                          // expected-note{{previous definition}}
 };
 
 void f2(int) { } // expected-note{{previous definition}}
 void f4(int) { } // expected-note{{previous definition}}
 
-X1<int> x1a; // expected-note 6{{in instantiation of}}
+X1<int> x1a; // expected-note 7{{in instantiation of}}
 
 void f3(int) { } // expected-note{{previous definition}}
 void f5(int) { } // expected-note{{previous definition}}
 
-X1<float> x1b;
+X1<float> x1b; 
 
 
 X1<double> *X0d() { return 0;}
+
+template<typename T>
+struct X2 {
+  friend void g0(T) { } // expected-error{{redefinition of 'g0'}}
+};
+
+template<typename T>
+struct X3 {
+  friend void g0(T) { } // expected-note{{previous definition is here}}
+};
+
+X2<float> x2; // expected-note{{in instantiation of}}
+X3<float> x3;
-- 
2.40.0