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.

Pick-to: 5.15 6.2 6.3
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>

2 files changed, 14 insertions, 7 deletions

diff --git a/src/plugins/platforms/windows/qwindowsglcontext.cpp b/src/plugins/platforms/windows/qwindowsglcontext.cpp
index a3039d3b8e..c3bfa2a6f4 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 59bdb38fad..e8d10e3555 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>
@@ -350,7 +351,7 @@ 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")));