From 006768903cb6586098218822129d622737848299 Mon Sep 17 00:00:00 2001
From: Zsolt Parragi <zsolt.parragi@cancellar.hu>
Date: Tue, 6 Nov 2018 20:40:18 +0100
Subject: Work around clang-cl breakage on make_unique/std::forward

Clang on Windows with the MSVC ABI produces link errors of the
form `unresolved std::_Iosb<int>::{app,_Openmode} in ...`.
Use a temporary variable to forward as lvalue rather than rvalue
to work around the problem.
---
 Source/cmExportFileGenerator.cxx              | 3 ++-
 Source/cmExportLibraryDependenciesCommand.cxx | 3 ++-
 2 files changed, 4 insertions(+), 2 deletions(-)

diff --git a/Source/cmExportFileGenerator.cxx b/Source/cmExportFileGenerator.cxx
index c8f743a..a12e0c4 100644
--- a/Source/cmExportFileGenerator.cxx
+++ b/Source/cmExportFileGenerator.cxx
@@ -70,8 +70,9 @@ bool cmExportFileGenerator::GenerateImportFile()
   std::unique_ptr<cmsys::ofstream> foutPtr;
   if (this->AppendMode) {
     // Open for append.
+    auto openmodeApp = std::ios::app;
     foutPtr = cm::make_unique<cmsys::ofstream>(this->MainImportFile.c_str(),
-                                               std::ios::app);
+                                               openmodeApp);
   } else {
     // Generate atomically and with copy-if-different.
     std::unique_ptr<cmGeneratedFileStream> ap(
diff --git a/Source/cmExportLibraryDependenciesCommand.cxx b/Source/cmExportLibraryDependenciesCommand.cxx
index b4b2962..e542e50 100644
--- a/Source/cmExportLibraryDependenciesCommand.cxx
+++ b/Source/cmExportLibraryDependenciesCommand.cxx
@@ -50,8 +50,9 @@ void cmExportLibraryDependenciesCommand::ConstFinalPass() const
   // Use copy-if-different if not appending.
   std::unique_ptr<cmsys::ofstream> foutPtr;
   if (this->Append) {
+    const auto openmodeApp = std::ios::app;
     foutPtr =
-      cm::make_unique<cmsys::ofstream>(this->Filename.c_str(), std::ios::app);
+      cm::make_unique<cmsys::ofstream>(this->Filename.c_str(), openmodeApp);
   } else {
     std::unique_ptr<cmGeneratedFileStream> ap(
       new cmGeneratedFileStream(this->Filename, true));
-- 
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