r192166 - Fix linkage calculation of auto member functions returning lambdas

[Faisal Vali]

Author: faisalv
Date: Mon Oct  7 23:15:04 2013
New Revision: 192166

URL: http://llvm.org/viewvc/llvm-project?rev=192166&view=rev
Log:
Fix linkage calculation of auto member functions returning lambdas

As described by Richard in https://groups.google.com/a/isocpp.org/d/msg/std-discussion/S1kmj0wF5-g/fb6agEYoL2IJ

we should allow:

template<typename S>
struct A {

template<typename T> static auto default_lambda() {
  return [](const T&) { return 42; };
}

template<class U = decltype(default_lambda<S>())>
  U func(U u = default_lambda<S>()) { return u; }

};

int run2 = A<double>{}.func()(3.14);

int run3 = A<char>{}.func()('a');

This patch allows the code using the same trickery that was used to allow the code in non-member functions at namespace scope.


Please see http://llvm-reviews.chandlerc.com/D1844 for richard's approval.

Added:
    cfe/trunk/test/CodeGenCXX/lambda-expressions-inside-auto-functions.cpp
Modified:
    cfe/trunk/lib/AST/Decl.cpp

Modified: cfe/trunk/lib/AST/Decl.cpp
URL: http://llvm.org/viewvc/llvm-project/cfe/trunk/lib/AST/Decl.cpp?rev=192166&r1=192165&r2=192166&view=diff
==============================================================================
--- cfe/trunk/lib/AST/Decl.cpp (original)
+++ cfe/trunk/lib/AST/Decl.cpp Mon Oct  7 23:15:04 2013
@@ -702,8 +702,8 @@ static LinkageInfo getLVForNamespaceScop
       // require looking at the linkage of this function, and we don't need this
       // for correctness because the type is not part of the function's
       // signature.
-      // FIXME: This is a hack. We should be able to solve this circularity some
-      // other way.
+      // FIXME: This is a hack. We should be able to solve this circularity and 
+      // the one in getLVForClassMember for Functions some other way.
       QualType TypeAsWritten = Function->getType();
       if (TypeSourceInfo *TSI = Function->getTypeSourceInfo())
         TypeAsWritten = TSI->getType();
@@ -830,9 +830,20 @@ static LinkageInfo getLVForClassMember(c
   if (const CXXMethodDecl *MD = dyn_cast<CXXMethodDecl>(D)) {
     // If the type of the function uses a type with unique-external
     // linkage, it's not legally usable from outside this translation unit.
-    if (MD->getType()->getLinkage() == UniqueExternalLinkage)
-      return LinkageInfo::uniqueExternal();
-
+    // But only look at the type-as-written. If this function has an auto-deduced
+    // return type, we can't compute the linkage of that type because it could
+    // require looking at the linkage of this function, and we don't need this
+    // for correctness because the type is not part of the function's
+    // signature.
+    // FIXME: This is a hack. We should be able to solve this circularity and the
+    // one in getLVForNamespaceScopeDecl for Functions some other way.
+    {
+      QualType TypeAsWritten = MD->getType();
+      if (TypeSourceInfo *TSI = MD->getTypeSourceInfo())
+        TypeAsWritten = TSI->getType();
+      if (TypeAsWritten->getLinkage() == UniqueExternalLinkage)
+        return LinkageInfo::uniqueExternal();
+    }
     // If this is a method template specialization, use the linkage for
     // the template parameters and arguments.
     if (FunctionTemplateSpecializationInfo *spec

Added: cfe/trunk/test/CodeGenCXX/lambda-expressions-inside-auto-functions.cpp
URL: http://llvm.org/viewvc/llvm-project/cfe/trunk/test/CodeGenCXX/lambda-expressions-inside-auto-functions.cpp?rev=192166&view=auto
==============================================================================
--- cfe/trunk/test/CodeGenCXX/lambda-expressions-inside-auto-functions.cpp (added)
+++ cfe/trunk/test/CodeGenCXX/lambda-expressions-inside-auto-functions.cpp Mon Oct  7 23:15:04 2013
@@ -0,0 +1,77 @@
+// RUN: %clang_cc1 -triple x86_64-apple-darwin10.0.0 -fblocks -emit-llvm -o - %s -fexceptions -std=c++1y | FileCheck %s
+
+// CHECK-LABEL: define void @_ZN19non_inline_function3fooEv
+// CHECK-LABEL: define internal void @"_ZZN19non_inline_function3fooEvENK3$_0clEi"(%class.anon
+// CHECK-LABEL: define internal signext i8 @"_ZZZN19non_inline_function3fooEvENK3$_0clEiENKUlcE_clEc"(%class.anon
+// CHECK-LABEL: define linkonce_odr void @_ZN19non_inline_function4foo2IiEEDav()
+namespace non_inline_function {
+auto foo() {
+  auto L = [](int a) {
+    return [](char b) {
+     return b;
+    };
+  };
+  L(3)('a');
+  return L;
+}
+
+template<typename T> 
+auto foo2() {
+  return [](const T&) { return 42; };
+}
+
+auto use = foo2<int>();
+
+}
+//CHECK-LABEL: define linkonce_odr void @_ZN22inline_member_function1X3fooEv(%"struct.inline_member_function::X"* %this)
+//CHECK-LABEL: define linkonce_odr void @_ZZN22inline_member_function1X3fooEvENKUliE_clEi(%class.anon
+//CHECK-LABEL: define linkonce_odr signext i8 @_ZZZN22inline_member_function1X3fooEvENKUliE_clEiENKUlcE_clEc(%class.anon
+
+namespace inline_member_function {
+struct X {
+auto foo() {
+  auto L = [](int a) {
+    return [](char b) {
+     return b;
+    };
+  };
+  return L;
+}
+};
+
+auto run1 = X{}.foo()(3)('a');
+
+template<typename S>
+struct A {
+  template<typename T> static auto default_lambda() {
+    return [](const T&) { return 42; };
+  }
+
+  template<class U = decltype(default_lambda<S>())>
+    U func(U u = default_lambda<S>()) { return u; }
+  
+  template<class T> auto foo() { return [](const T&) { return 42; }; }
+};
+//CHECK-LABEL: define linkonce_odr i32 @_ZZN22inline_member_function1AIdE14default_lambdaIdEEDavENKUlRKdE_clES5_(%class.anon
+int run2 = A<double>{}.func()(3.14);
+
+//CHECK-LABEL: define linkonce_odr i32 @_ZZN22inline_member_function1AIcE14default_lambdaIcEEDavENKUlRKcE_clES5_(%class.anon
+int run3 = A<char>{}.func()('a');
+} // end inline_member_function
+
+
+// CHECK-LABEL: define linkonce_odr void @_ZN15inline_function3fooEv()
+// CHECK: define linkonce_odr void @_ZZN15inline_function3fooEvENKUliE_clEi(%class.anon
+// CHECK: define linkonce_odr signext i8 @_ZZZN15inline_function3fooEvENKUliE_clEiENKUlcE_clEc(%class.anon
+namespace inline_function {
+inline auto foo() {
+  auto L = [](int a) {
+    return [](char b) {
+     return b;
+    };
+  };
+  return L;
+}
+auto use = foo()(3)('a');
+}
+