From 84df6e99b8835465ae6319f055d14feb9ddcf777 Mon Sep 17 00:00:00 2001
From: Bruno Cardoso Lopes <bruno.cardoso@gmail.com>
Date: Wed, 1 Mar 2017 19:18:42 +0000
Subject: [PATCH] [PCH] Avoid VarDecl emission attempt if no owning module
 avaiable

This is a stopgap fix for PR31863, a regression introduced in r276159.

Consider this snippet:

struct FVector;
struct FVector {};
struct FBox {
  FVector Min;
  FBox(int);
};
namespace {
FBox InvalidBoundingBox(0);
}

While parsing the DECL_VAR for 'struct FBox', clang recursively read all the
dep decls until it finds the DECL_CXX_RECORD forward declaration for 'struct
FVector'. Then, it resumes all the way up back to DECL_VAR handling in
`ReadDeclRecord`, where it checks if `isConsumerInterestedIn` for the decl.

One of the condition for `isConsumerInterestedIn` to return false is if the
VarDecl is imported from a module `D->getImportedOwningModule()`, because it
will get emitted when we import the relevant module. However, before checking
if it comes from a module, clang checks if `Ctx.DeclMustBeEmitted(D)`, which
triggers the emission of 'struct FBox'. Since one of its fields is still
incomplete, it crashes.

Instead, check if `D->getImportedOwningModule()` is true before calling
`Ctx.DeclMustBeEmitted(D)`.

Differential Revision: https://reviews.llvm.org/D29753

rdar://problem/30173654

llvm-svn: 296656
---
 clang/lib/Serialization/ASTReaderDecl.cpp |  4 ++--
 clang/test/PCH/empty-def-fwd-struct.h     | 12 ++++++++++++
 2 files changed, 14 insertions(+), 2 deletions(-)
 create mode 100644 clang/test/PCH/empty-def-fwd-struct.h

diff --git a/clang/lib/Serialization/ASTReaderDecl.cpp b/clang/lib/Serialization/ASTReaderDecl.cpp
index 5b9117440920..93d0f9384fff 100644
--- a/clang/lib/Serialization/ASTReaderDecl.cpp
+++ b/clang/lib/Serialization/ASTReaderDecl.cpp
@@ -2530,8 +2530,8 @@ static bool isConsumerInterestedIn(ASTContext &Ctx, Decl *D, bool HasBody) {
 
   // An ImportDecl or VarDecl imported from a module will get emitted when
   // we import the relevant module.
-  if ((isa<ImportDecl>(D) || isa<VarDecl>(D)) && Ctx.DeclMustBeEmitted(D) &&
-      D->getImportedOwningModule())
+  if ((isa<ImportDecl>(D) || isa<VarDecl>(D)) && D->getImportedOwningModule() &&
+      Ctx.DeclMustBeEmitted(D))
     return false;
 
   if (isa<FileScopeAsmDecl>(D) || 
diff --git a/clang/test/PCH/empty-def-fwd-struct.h b/clang/test/PCH/empty-def-fwd-struct.h
new file mode 100644
index 000000000000..dda9827ac8f4
--- /dev/null
+++ b/clang/test/PCH/empty-def-fwd-struct.h
@@ -0,0 +1,12 @@
+// RUN: %clang_cc1 -emit-pch -x c++-header %s -std=c++14 -o %t.pch
+// RUN: %clang_cc1 -emit-llvm-only -x c++ /dev/null -std=c++14 -include-pch %t.pch -o %t.o
+struct FVector;
+struct FVector {};
+struct FBox {
+  FVector Min;
+  FBox(int);
+};
+namespace {
+FBox InvalidBoundingBox(0);
+}
+