Merging r324059:

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r324059 | mstorsjo | 2018-02-02 07:22:35 +0100 (Fri, 02 Feb 2018) | 21 lines

[MinGW] Emit typeinfo locally for dllimported classes without key functions

This fixes building Qt as shared libraries with clang in MinGW
mode; previously subclasses of the QObjectData class (in other
DLLs than the base DLL) failed to find the typeinfo symbols
(that neither were emitted in the base DLL nor in the DLL
containing the subclass).

If the virtual destructor in the newly added testcase wouldn't
be pure (or if there'd be another non-pure virtual method),
it'd be a key function and things would work out even before this
change. Make sure to locally emit the typeinfo for these classes
as well.

This matches what GCC does in this specific testcase.

This fixes the root issue that spawned PR35146. (The difference
to GCC that is initially described in that bug still is present
though.)

Differential Revision: https://reviews.llvm.org/D42641
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git-svn-id: https://llvm.org/svn/llvm-project/cfe/branches/release_60@324219 91177308-0d34-0410-b5e6-96231b3b80d8

1 files changed, 5 insertions, 0 deletions

diff --git a/lib/CodeGen/ItaniumCXXABI.cpp b/lib/CodeGen/ItaniumCXXABI.cpp
index c375b82ea9..a3c2766dbb 100644
--- a/lib/CodeGen/ItaniumCXXABI.cpp
+++ b/lib/CodeGen/ItaniumCXXABI.cpp
@@ -2761,6 +2761,11 @@ static bool ShouldUseExternalRTTIDescriptor(CodeGenModule &CGM,
     // N.B. We must always emit the RTTI data ourselves if there exists a key
     // function.
     bool IsDLLImport = RD->hasAttr<DLLImportAttr>();
+
+    // Don't import the RTTI but emit it locally.
+    if (CGM.getTriple().isWindowsGNUEnvironment() && IsDLLImport)
+      return false;
+
     if (CGM.getVTables().isVTableExternal(RD))
       return IsDLLImport && !CGM.getTriple().isWindowsItaniumEnvironment()
                  ? false