From: Fariborz Jahanian <fjahanian@apple.com>
Date: Mon, 19 Oct 2009 19:18:20 +0000 (+0000)
Subject: Copy conversion of an expression to its base class
X-Git-Url: https://granicus.if.org/sourcecode?a=commitdiff_plain;h=3759a0361ec00e03584cb6f9ce64fb1f1c947336;p=clang

Copy conversion of an expression to its base class
is a standard convesion and not a user-defined
conversion.


git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@84525 91177308-0d34-0410-b5e6-96231b3b80d8
---

diff --git a/lib/Sema/SemaOverload.cpp b/lib/Sema/SemaOverload.cpp
index 0f2256b6bc..436b3d1e27 100644
--- a/lib/Sema/SemaOverload.cpp
+++ b/lib/Sema/SemaOverload.cpp
@@ -2539,6 +2539,18 @@ Sema::AddConversionCandidate(CXXConversionDecl *Conversion,
     Candidate.Viable = false;
     return;
   }
+  
+  // We won't go through a user-define type conversion function to convert a 
+  // derived to base as such conversions are given Conversion Rank. They only
+  // go through a copy constructor. 13.3.3.1.2-p4 [over.ics.user]
+  QualType FromCanon
+    = Context.getCanonicalType(From->getType().getUnqualifiedType());
+  QualType ToCanon = Context.getCanonicalType(ToType).getUnqualifiedType();
+  if (FromCanon == ToCanon || IsDerivedFrom(FromCanon, ToCanon)) {
+    Candidate.Viable = false;
+    return;
+  }
+  
 
   // To determine what the conversion from the result of calling the
   // conversion function to the type we're eventually trying to
diff --git a/test/CodeGenCXX/derived-to-base-conv.cpp b/test/CodeGenCXX/derived-to-base-conv.cpp
index 218116e346..0c89019511 100644
--- a/test/CodeGenCXX/derived-to-base-conv.cpp
+++ b/test/CodeGenCXX/derived-to-base-conv.cpp
@@ -5,6 +5,7 @@
 // RUN: true
 
 extern "C" int printf(...);
+extern "C" void exit(int);
 
 struct A {
  A (const A&) { printf("A::A(const A&)\n"); }
@@ -44,8 +45,35 @@ int main()
     func(x);
 }
 
+struct Base;
+
+struct Root {
+  operator Base&() { exit(1); }
+};
+
+struct Derived;
+
+struct Base : Root {
+  Base(const Base&) { printf("Base::(const Base&)\n"); }
+  Base() { printf("Base::Base()\n"); }
+  operator Derived&() { exit(1); }
+};
+
+struct Derived : Base {
+};
+
+void foo(Base) {}
+
+void test(Derived bb)
+{
+	// CHECK-LP64-NOT: call     __ZN4BasecvR7DerivedEv
+	// CHECK-LP32-NOT: call     L__ZN4BasecvR7DerivedEv
+        foo(bb);
+}
 // CHECK-LP64: call     __ZN1XcvR1BEv
 // CHECK-LP64: call     __ZN1AC1ERKS_
 
 // CHECK-LP32: call     L__ZN1XcvR1BEv
 // CHECK-LP32: call     L__ZN1AC1ERKS_
+
+