Add QComHelper class for dealing with COM on Windows

Unifies our approach to calling CoInitializeEx and CoUninitialize,
removing a lot of boilerplate in the process, and also fixes a few
bugs where we would incorrectly balance our calls to CoInitializeEx
and CoUninitialize.

The optimistic approach of qfilesystemengine_win.cpp of calling
CoCreateInstance without initializing the COM library explicitly
has been removed, as calling CoInitializeEx should be a noop in
the situation where it's already been loaded.

Change-Id: I9e2ec101678c2ebb9946504b5e8034e58f1bb56a
Reviewed-by: Oliver Wolff <oliver.wolff@qt.io>

1 files changed, 2 insertions, 9 deletions

diff --git a/tests/auto/corelib/io/qfile/tst_qfile.cpp b/tests/auto/corelib/io/qfile/tst_qfile.cpp
index 41dfd12d4f..cbe46ca041 100644
--- a/tests/auto/corelib/io/qfile/tst_qfile.cpp
+++ b/tests/auto/corelib/io/qfile/tst_qfile.cpp
@@ -22,6 +22,7 @@
 #include <private/qabstractfileengine_p.h>
 #include <private/qfsfileengine_p.h>
 #include <private/qfilesystemengine_p.h>
+#include <QtCore/private/qfunctions_win_p.h>
 
 #include <QtTest/private/qemulationdetector_p.h>
 
@@ -1540,13 +1541,9 @@ static QString getWorkingDirectoryForLink(const QString &linkFileName)
     bool neededCoInit = false;
     QString ret;
 
+    QComHelper comHelper;
     IShellLink *psl;
     HRESULT hres = CoCreateInstance(CLSID_ShellLink, NULL, CLSCTX_INPROC_SERVER, IID_IShellLink, (void **)&psl);
-    if (hres == CO_E_NOTINITIALIZED) { // COM was not initialized
-        neededCoInit = true;
-        CoInitializeEx(nullptr, COINIT_APARTMENTTHREADED | COINIT_DISABLE_OLE1DDE);
-        hres = CoCreateInstance(CLSID_ShellLink, NULL, CLSCTX_INPROC_SERVER, IID_IShellLink, (void **)&psl);
-    }
 
     if (SUCCEEDED(hres)) {    // Get pointer to the IPersistFile interface.
         IPersistFile *ppf;
@@ -1565,10 +1562,6 @@ static QString getWorkingDirectoryForLink(const QString &linkFileName)
         psl->Release();
     }
 
-    if (neededCoInit) {
-        CoUninitialize();
-    }
-
     return ret;
 }
 #endif