From: Balaji V. Iyer <bviyer@gmail.com>
Date: Wed, 8 Aug 2018 00:01:21 +0000 (+0000)
Subject: [CodeGen] IncompleteArray Support
X-Git-Url: https://granicus.if.org/sourcecode?a=commitdiff_plain;h=4d9977bdf0ba2733fd844e195d53650d5a9e5cb9;p=clang

[CodeGen] IncompleteArray Support

Added code to support ArrayType that is not ConstantArray.

https://reviews.llvm.org/D49952
rdar://42476155




git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@339207 91177308-0d34-0410-b5e6-96231b3b80d8
---

diff --git a/lib/CodeGen/CGExprConstant.cpp b/lib/CodeGen/CGExprConstant.cpp
index 68766479a5..651b05a26f 100644
--- a/lib/CodeGen/CGExprConstant.cpp
+++ b/lib/CodeGen/CGExprConstant.cpp
@@ -1968,6 +1968,16 @@ llvm::Constant *ConstantEmitter::tryEmitPrivate(const APValue &Value,
       Elts.push_back(C);
     }
 
+    // This means that the array type is probably "IncompleteType" or some
+    // type that is not ConstantArray.
+    if (CAT == nullptr && CommonElementType == nullptr && !NumInitElts) {
+      const ArrayType *AT = CGM.getContext().getAsArrayType(DestType);
+      CommonElementType = CGM.getTypes().ConvertType(AT->getElementType());
+      llvm::ArrayType *AType = llvm::ArrayType::get(CommonElementType,
+                                                    NumElements);
+      return llvm::ConstantAggregateZero::get(AType);
+    }
+
     return EmitArrayConstant(CGM, CAT, CommonElementType, NumElements, Elts,
                              Filler);
   }
diff --git a/test/CodeGenCXX/empty-struct-init-list.cpp b/test/CodeGenCXX/empty-struct-init-list.cpp
new file mode 100644
index 0000000000..d1698b0e43
--- /dev/null
+++ b/test/CodeGenCXX/empty-struct-init-list.cpp
@@ -0,0 +1,12 @@
+// RUN: %clang_cc1 -std=c++11 -emit-llvm -o - %s | FileCheck %s
+// RUN: %clang_cc1 -std=c++14 -emit-llvm -o - %s | FileCheck %s
+// RUN: %clang_cc1 -std=c++17 -emit-llvm -o - %s | FileCheck %s
+
+// CHECK: struct.a
+typedef struct { } a;
+typedef struct {
+  a b[];
+} c;
+
+// CHECK: global %struct.c zeroinitializer, align 1
+c d{ };