r296656 - [PCH] Avoid VarDecl emission attempt if no owning module avaiable

[Bruno Cardoso Lopes via cfe-commits]

Author: bruno
Date: Wed Mar  1 13:18:42 2017
New Revision: 296656

URL: http://llvm.org/viewvc/llvm-project?rev=296656&view=rev
Log:
[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

Added:
    cfe/trunk/test/PCH/empty-def-fwd-struct.h
Modified:
    cfe/trunk/lib/Serialization/ASTReaderDecl.cpp

Modified: cfe/trunk/lib/Serialization/ASTReaderDecl.cpp
URL: http://llvm.org/viewvc/llvm-project/cfe/trunk/lib/Serialization/ASTReaderDecl.cpp?rev=296656&r1=296655&r2=296656&view=diff
==============================================================================
--- cfe/trunk/lib/Serialization/ASTReaderDecl.cpp (original)
+++ cfe/trunk/lib/Serialization/ASTReaderDecl.cpp Wed Mar  1 13:18:42 2017
@@ -2530,8 +2530,8 @@ static bool isConsumerInterestedIn(ASTCo
 
   // 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) || 

Added: cfe/trunk/test/PCH/empty-def-fwd-struct.h
URL: http://llvm.org/viewvc/llvm-project/cfe/trunk/test/PCH/empty-def-fwd-struct.h?rev=296656&view=auto
==============================================================================
--- cfe/trunk/test/PCH/empty-def-fwd-struct.h (added)
+++ cfe/trunk/test/PCH/empty-def-fwd-struct.h Wed Mar  1 13:18:42 2017
@@ -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);
+}
+