From de8eaa2bf22ab0a59118289ee8b97f6ac6a97196 Mon Sep 17 00:00:00 2001
From: Faisal Vali <faisalv@yahoo.com>
Date: Tue, 1 Oct 2013 02:51:53 +0000
Subject: [PATCH] Fix computation of linkage within nested lambdas.

When nested C++11 lambdas are used in NSDMI's - this patch prevents infinite recursion by computing the linkage of any nested lambda by determining the linkage of the outermost enclosing lambda (which might inherit its linkage from its parent).

See http://llvm-reviews.chandlerc.com/D1783 for Doug's approval.

[On a related note, I need this patch so as to pass tests of transformations of nested lambdas returned from member functions]


git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@191727 91177308-0d34-0410-b5e6-96231b3b80d8
---
 lib/AST/Decl.cpp                              | 34 +++++++++++--
 .../lambda-expressions-nested-linkage.cpp     | 50 +++++++++++++++++++
 test/SemaCXX/lambda-expressions.cpp           | 18 +++++++
 3 files changed, 99 insertions(+), 3 deletions(-)
 create mode 100644 test/CodeGenCXX/lambda-expressions-nested-linkage.cpp

diff --git a/lib/AST/Decl.cpp b/lib/AST/Decl.cpp
index 57bf94c0f0..a0b3894a08 100644
--- a/lib/AST/Decl.cpp
+++ b/lib/AST/Decl.cpp
@@ -1092,6 +1092,19 @@ static LinkageInfo getLVForLocalDecl(const NamedDecl *D,
                      LV.isVisibilityExplicit());
 }
 
+static inline const CXXRecordDecl*
+getOutermostEnclosingLambda(const CXXRecordDecl *Record) {
+  const CXXRecordDecl *Ret = Record;
+  while (Record && Record->isLambda()) {
+    Ret = Record;
+    if (!Record->getParent()) break;
+    // Get the Containing Class of this Lambda Class
+    Record = dyn_cast_or_null<CXXRecordDecl>(
+      Record->getParent()->getParent());
+  }
+  return Ret;
+}
+
 static LinkageInfo computeLVForDecl(const NamedDecl *D,
                                     LVComputationKind computation) {
   // Objective-C: treat all Objective-C declarations as having external
@@ -1122,9 +1135,24 @@ static LinkageInfo computeLVForDecl(const NamedDecl *D,
           return LinkageInfo::internal();
         }
 
-        // This lambda has its linkage/visibility determined by its owner.
-        return getLVForClosure(D->getDeclContext()->getRedeclContext(),
-                               Record->getLambdaContextDecl(), computation);
+        // This lambda has its linkage/visibility determined:
+        //  - either by the outermost lambda if that lambda has no mangling 
+        //    number. 
+        //  - or by the parent of the outer most lambda
+        // This prevents infinite recursion in settings such as nested lambdas 
+        // used in NSDMI's, for e.g. 
+        //  struct L {
+        //    int t{};
+        //    int t2 = ([](int a) { return [](int b) { return b; };})(t)(t);    
+        //  };
+        const CXXRecordDecl *OuterMostLambda = 
+            getOutermostEnclosingLambda(Record);
+        if (!OuterMostLambda->getLambdaManglingNumber())
+          return LinkageInfo::internal();
+        
+        return getLVForClosure(
+                  OuterMostLambda->getDeclContext()->getRedeclContext(),
+                  OuterMostLambda->getLambdaContextDecl(), computation);
       }
       
       break;
diff --git a/test/CodeGenCXX/lambda-expressions-nested-linkage.cpp b/test/CodeGenCXX/lambda-expressions-nested-linkage.cpp
new file mode 100644
index 0000000000..accc5d2c4c
--- /dev/null
+++ b/test/CodeGenCXX/lambda-expressions-nested-linkage.cpp
@@ -0,0 +1,50 @@
+// RUN: %clang_cc1 -triple x86_64-apple-darwin10.0.0 -fblocks -emit-llvm -o - %s -fexceptions -std=c++11 | 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
+namespace non_inline_function {
+void foo() {
+  auto L = [](int a) {
+    return [](char b) {
+     return b;
+    };
+  };
+  L(3)('a');
+}
+}
+
+namespace non_template {
+  struct L {
+    int t = ([](int a) { return [](int b) { return b; };})(2)(3);    
+  };
+  L l; 
+}
+
+namespace lambdas_in_NSDMIs_template_class {
+template<class T>
+struct L {
+    T t2 = ([](int a) { return [](int b) { return b; };})(T{})(T{});    
+};
+L<int> l;
+}
+
+// CHECK-LABEL: define linkonce_odr i32 @_ZN15inline_function3fooEv
+// CHECK: define linkonce_odr void @_ZZN15inline_function3fooEvENKUliE_clEi
+// CHECK: define linkonce_odr signext i8 @_ZZZN15inline_function3fooEvENKUliE_clEiENKUlcE_clEc
+namespace inline_function {
+inline int foo() {
+  auto L = [](int a) {
+    return [](char b) {
+     return b;
+    };
+  };
+  L(3)('a');
+}
+int use = foo();
+}
+// CHECK: define linkonce_odr void @_ZNK32lambdas_in_NSDMIs_template_class1LIiEUliE_clEi(%class.anon
+// CHECK: define linkonce_odr i32 @_ZZNK32lambdas_in_NSDMIs_template_class1LIiEUliE_clEiENKUliE_clEi(%class.anon
+
+// CHECK: define linkonce_odr void @_ZNK12non_template1L1tMUliE_clEi(%class.anon
+// CHECK: define linkonce_odr i32 @_ZZNK12non_template1L1tMUliE_clEiENKUliE_clEi(%class.anon
diff --git a/test/SemaCXX/lambda-expressions.cpp b/test/SemaCXX/lambda-expressions.cpp
index e8e2eb612a..e2904247c4 100644
--- a/test/SemaCXX/lambda-expressions.cpp
+++ b/test/SemaCXX/lambda-expressions.cpp
@@ -265,3 +265,21 @@ namespace TypeDeduction {
 #endif
   }
 }
+
+
+namespace lambdas_in_NSDMIs {
+  template<class T>
+  struct L {
+      T t{};
+      T t2 = ([](int a) { return [](int b) { return b; };})(t)(t);    
+  };
+  L<int> l; 
+  
+  namespace non_template {
+    struct L {
+      int t = 0;
+      int t2 = ([](int a) { return [](int b) { return b; };})(t)(t);    
+    };
+    L l; 
+  }
+}
\ No newline at end of file
-- 
2.40.0