[clang] 2926917 - [clang] Fix linkage of nested lambdas.

[Michael Liao via cfe-commits]

Author: Michael Liao
Date: 2020-02-07T13:24:21-05:00
New Revision: 2926917f430d705f084813b63a40fafc61872524

URL: https://github.com/llvm/llvm-project/commit/2926917f430d705f084813b63a40fafc61872524
DIFF: https://github.com/llvm/llvm-project/commit/2926917f430d705f084813b63a40fafc61872524.diff

LOG: [clang] Fix linkage of nested lambdas.

patch from Philippe Daouadi <blastrock at free.fr>

This is an attempt to fix
[PR#44368](https://bugs.llvm.org/show_bug.cgi?id=44368)

This effectively reverts [D1783](https://reviews.llvm.org/D1783). It
doesn't break the current tests and fixes the test that this commit
adds.

We now decide of a lambda linkage only depending on the visibility of
its parent context.

Differential Revision: https://reviews.llvm.org/D73701

Added: 
    

Modified: 
    clang/lib/AST/Decl.cpp
    clang/test/CodeGenCXX/lambda-expressions-nested-linkage.cpp

Removed: 
    


################################################################################
diff  --git a/clang/lib/AST/Decl.cpp b/clang/lib/AST/Decl.cpp
index 0d30f64b992e..216137bf74f9 100644
--- a/clang/lib/AST/Decl.cpp
+++ b/clang/lib/AST/Decl.cpp
@@ -1318,19 +1318,6 @@ LinkageInfo LinkageComputer::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;
-}
-
 LinkageInfo LinkageComputer::computeLVForDecl(const NamedDecl *D,
                                               LVComputationKind computation,
                                               bool IgnoreVarTypeLinkage) {
@@ -1396,25 +1383,9 @@ LinkageInfo LinkageComputer::computeLVForDecl(const NamedDecl *D,
           return getInternalLinkageFor(D);
         }
 
-        // 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->hasKnownLambdaInternalLinkage() ||
-            !OuterMostLambda->getLambdaManglingNumber())
-          return getInternalLinkageFor(D);
-
         return getLVForClosure(
-                  OuterMostLambda->getDeclContext()->getRedeclContext(),
-                  OuterMostLambda->getLambdaContextDecl(), computation);
+                  Record->getDeclContext()->getRedeclContext(),
+                  Record->getLambdaContextDecl(), computation);
       }
 
       break;

diff  --git a/clang/test/CodeGenCXX/lambda-expressions-nested-linkage.cpp b/clang/test/CodeGenCXX/lambda-expressions-nested-linkage.cpp
index 9a449874cb85..6b45645c9e2d 100644
--- a/clang/test/CodeGenCXX/lambda-expressions-nested-linkage.cpp
+++ b/clang/test/CodeGenCXX/lambda-expressions-nested-linkage.cpp
@@ -1,4 +1,5 @@
 // RUN: %clang_cc1 -triple x86_64-apple-darwin10.0.0 -fblocks -emit-llvm -o - %s -fexceptions -std=c++11 | FileCheck %s
+// RUN: %clang_cc1 -triple x86_64-apple-darwin10.0.0 -fblocks -emit-llvm -o - %s -fexceptions -std=c++14 | FileCheck --check-prefixes=CHECK,CXX14 %s
 
 // CHECK-LABEL: define void @_ZN19non_inline_function3fooEv()
 // CHECK-LABEL: define internal void @"_ZZN19non_inline_function3fooEvENK3$_0clEi"(%class.anon
@@ -51,3 +52,18 @@ inline int foo() {
 }
 int use = foo();
 }
+
+#if __cplusplus >= 201402L
+// CXX14-LABEL: define internal void @"_ZZZN32lambda_capture_in_generic_lambda3fooIiEEDavENKUlT_E_clIZNS_L1fEvE3$_1EEDaS1_ENKUlvE_clEv"
+namespace lambda_capture_in_generic_lambda {
+template <typename T> auto foo() {
+  return [](auto func) {
+    [func] { func(); }();
+  };
+}
+static void f() {
+  foo<int>()([] { });
+}
+void f1() { f(); }
+}
+#endif