Windows: use QSystemLibrary instead of LoadLibrary directly

Using QSystemLibrary ensures that it will only use the expected copy of
the system library and not one that has been placed in the application's
working directory or elsewhere in the PATH environment variable.

Change-Id: Ic4234334f73482b38ee5f06345bf11f8c029edc5
Reviewed-by: Laszlo Agocs <laszlo.agocs@qt.io>
Reviewed-by: Thiago Macieira <thiago.macieira@intel.com>
Reviewed-by: Qt CI Bot <qt_ci_bot@qt-project.org>
(cherry picked from commit a14f2d59141e05d4c8e116895e918638b920611d)
Reviewed-by: Qt Cherry-pick Bot <cherrypick_bot@qt-project.org>

2 files changed, 14 insertions, 7 deletions

diff --git a/src/plugins/platforms/windows/qwindowsglcontext.cpp b/src/plugins/platforms/windows/qwindowsglcontext.cpp
index 1a7be0d271..9a8506d971 100644
--- a/src/plugins/platforms/windows/qwindowsglcontext.cpp
+++ b/src/plugins/platforms/windows/qwindowsglcontext.cpp
@@ -47,7 +47,7 @@
 #include <QtGui/qcolorspace.h>
 #include <QtGui/qguiapplication.h>
 #include <qpa/qplatformnativeinterface.h>
-
+#include <private/qsystemlibrary_p.h>
 #include <algorithm>
 
 #include <wingdi.h>
@@ -162,19 +162,25 @@ QFunctionPointer QWindowsOpengl32DLL::resolve(const char *name)
 
 bool QWindowsOpengl32DLL::init(bool softwareRendering)
 {
-    const QByteArray opengl32 = QByteArrayLiteral("opengl32.dll");
-    const QByteArray swopengl = QByteArrayLiteral("opengl32sw.dll");
+    const QByteArray opengl32 = QByteArrayLiteral("opengl32");
+    const QByteArray swopengl = QByteArrayLiteral("opengl32sw");
+    bool useSystemLib = false;
 
     QByteArray openglDll = qgetenv("QT_OPENGL_DLL");
-    if (openglDll.isEmpty())
+    if (openglDll.isEmpty()) {
         openglDll = softwareRendering ? swopengl : opengl32;
+        useSystemLib = !softwareRendering;
+    }
 
     openglDll = openglDll.toLower();
     m_nonOpengl32 = openglDll != opengl32;
 
     qCDebug(lcQpaGl) << "Qt: Using WGL and OpenGL from" << openglDll;
 
-    m_lib = ::LoadLibraryA(openglDll.constData());
+    if (useSystemLib)
+        m_lib = QSystemLibrary::load((wchar_t*)(QString::fromLatin1(openglDll).utf16()));
+    else
+        m_lib = LoadLibraryA(openglDll.constData());
     if (!m_lib) {
         qErrnoWarning(::GetLastError(), "Failed to load %s", openglDll.constData());
         return false;
@@ -184,7 +190,7 @@ bool QWindowsOpengl32DLL::init(bool softwareRendering)
         // Load opengl32.dll always. GDI functions like ChoosePixelFormat do
         // GetModuleHandle for opengl32.dll and behave differently (and call back into
         // opengl32) when the module is present. This is fine for dummy contexts and windows.
-        ::LoadLibraryA("opengl32.dll");
+        QSystemLibrary::load(L"opengl32");
     }
 
     wglCreateContext = reinterpret_cast<HGLRC (WINAPI *)(HDC)>(resolve("wglCreateContext"));
diff --git a/src/plugins/platforms/windows/qwindowsopengltester.cpp b/src/plugins/platforms/windows/qwindowsopengltester.cpp
index 0b1af47a65..1757b6a0dc 100644
--- a/src/plugins/platforms/windows/qwindowsopengltester.cpp
+++ b/src/plugins/platforms/windows/qwindowsopengltester.cpp
@@ -49,6 +49,7 @@
 #include <QtCore/qstandardpaths.h>
 #include <QtCore/qlibraryinfo.h>
 #include <QtCore/qhash.h>
+#include <private/qsystemlibrary_p.h>
 
 #ifndef QT_NO_OPENGL
 #include <private/qopengl_p.h>
@@ -358,7 +359,7 @@ bool QWindowsOpenGLTester::testDesktopGL()
 
     // Test #1: Load opengl32.dll and try to resolve an OpenGL 2 function.
     // This will typically fail on systems that do not have a real OpenGL driver.
-    lib = LoadLibraryA("opengl32.dll");
+    lib = QSystemLibrary::load(L"opengl32");
     if (lib) {
         CreateContext = reinterpret_cast<CreateContextType>(
             reinterpret_cast<QFunctionPointer>(::GetProcAddress(lib, "wglCreateContext")));