Simplify the QLibrary plugin-detection code

The reason why the scanning of files was restricted to Unix is lost in
history. My guess is that it was added *because* on Unix you couldn't
do the LoadLibrary trick to load without dependencies. That is, it
makes no comparison to whether scanning is faster than LoadLibrary.

So assume that scanning is faster, especially now that we have memory
mapping in QFile (it wasn't there in Qt 4.0).

This simplifies greatly the codebase because we no longer need to try
to load and later unload the library to check whether it is a Qt
plugin or not, nor deal with Windows non-C++ exceptions. Just scan on
all platforms.

Change-Id: If269e009bfb9920805ca1aa6c2b66aacdd5b26e9
Reviewed-by: Morten Johan Sørvig <morten.sorvig@digia.com>
Reviewed-by: Friedemann Kleint <Friedemann.Kleint@digia.com>
Reviewed-by: Lars Knoll <lars.knoll@digia.com>
Reviewed-by: Joerg Bornemann <joerg.bornemann@digia.com>

1 files changed, 12 insertions, 104 deletions

diff --git a/src/corelib/plugin/qlibrary.cpp b/src/corelib/plugin/qlibrary.cpp
index f015c3c236..92e60c2216 100644
--- a/src/corelib/plugin/qlibrary.cpp
+++ b/src/corelib/plugin/qlibrary.cpp
@@ -181,8 +181,6 @@ QT_BEGIN_NAMESPACE
 */
 
 
-#if defined(Q_OS_UNIX)
-
 static long qt_find_pattern(const char *s, ulong s_len,
                              const char *pattern, ulong p_len)
 {
@@ -229,7 +227,7 @@ static long qt_find_pattern(const char *s, ulong s_len,
                 information could not be read.
   Returns  true if version information is present and successfully read.
 */
-static bool qt_unix_query(const QString &library, QLibraryPrivate *lib)
+static bool findPatternUnloaded(const QString &library, QLibraryPrivate *lib)
 {
     QFile file(library);
     if (!file.open(QIODevice::ReadOnly)) {
@@ -321,8 +319,6 @@ static bool qt_unix_query(const QString &library, QLibraryPrivate *lib)
     return ret;
 }
 
-#endif // Q_OS_UNIX && !Q_OS_MAC
-
 static void installCoverageTool(QLibraryPrivate *libPrivate)
 {
 #ifdef __COVERAGESCANNER__
@@ -639,41 +635,18 @@ bool QLibrary::isLibrary(const QString &fileName)
 
 }
 
-#if defined (Q_OS_WIN) && defined(_MSC_VER) && _MSC_VER >= 1400  && !defined(Q_CC_INTEL)
-#define QT_USE_MS_STD_EXCEPTION 1
-const char* qt_try_versioninfo(void *pfn, bool *exceptionThrown)
-{
-    *exceptionThrown = false;
-    const char *szData = 0;
-    typedef const char * (*VerificationFunction)();
-    VerificationFunction func = reinterpret_cast<VerificationFunction>(pfn);
-    __try {
-        if(func)
-            szData =  func();
-    } __except(EXCEPTION_EXECUTE_HANDLER) {
-        *exceptionThrown = true;
-    }
-    return szData;
-}
-#endif
-
 typedef const char * (*QtPluginQueryVerificationDataFunction)();
 
-bool qt_get_metadata(QtPluginQueryVerificationDataFunction pfn, QLibraryPrivate *priv, bool *exceptionThrown)
+static bool qt_get_metadata(QtPluginQueryVerificationDataFunction pfn, QLibraryPrivate *priv)
 {
-    *exceptionThrown = false;
     const char *szData = 0;
     if (!pfn)
         return false;
-#ifdef QT_USE_MS_STD_EXCEPTION
-    szData = qt_try_versioninfo((void *)pfn, exceptionThrown);
-    if (*exceptionThrown)
-        return false;
-#else
+
     szData = pfn();
-#endif
     if (!szData)
         return false;
+
     QJsonDocument doc = QLibraryPrivate::fromRawMetaData(szData);
     if (doc.isNull())
         return false;
@@ -711,80 +684,15 @@ void QLibraryPrivate::updatePluginState()
     }
 #endif
 
-#if defined(Q_OS_UNIX)
     if (!pHnd) {
-        // use unix shortcut to avoid loading the library
-        success = qt_unix_query(fileName, this);
-    } else
-#endif
-    {
-        bool retryLoadLibrary = false;    // Only used on Windows with MS compiler.(false in other cases)
-        do {
-            bool temporary_load = false;
-#ifdef Q_OS_WIN
-            HMODULE hTempModule = 0;
-#endif
-            if (!pHnd) {
-#ifdef Q_OS_WIN
-                DWORD dwFlags = (retryLoadLibrary) ? 0: DONT_RESOLVE_DLL_REFERENCES;
-                //avoid 'Bad Image' message box
-                UINT oldmode = SetErrorMode(SEM_FAILCRITICALERRORS|SEM_NOOPENFILEERRORBOX);
-                hTempModule = ::LoadLibraryEx((wchar_t*)QDir::toNativeSeparators(fileName).utf16(), 0, dwFlags);
-                SetErrorMode(oldmode);
-#else
-                temporary_load =  load();
-#endif
-            }
-            QtPluginQueryVerificationDataFunction getMetaData = NULL;
-
-            bool exceptionThrown = false;
-            bool ret = false;
-#ifdef Q_OS_WIN
-            if (hTempModule) {
-                getMetaData = (QtPluginQueryVerificationDataFunction)
-#ifdef Q_OS_WINCE
-                    ::GetProcAddress(hTempModule, L"qt_plugin_query_metadata")
-#else
-                    ::GetProcAddress(hTempModule, "qt_plugin_query_metadata")
-#endif
-                        ;
-            } else
-#endif
-            {
-                getMetaData = (QtPluginQueryVerificationDataFunction) resolve("qt_plugin_query_metadata");
-            }
-
-            if (getMetaData)
-                ret = qt_get_metadata(getMetaData, this, &exceptionThrown);
-
-            if (temporary_load)
-                unload();
-            if (!exceptionThrown) {
-                if (ret) {
-                    success = true;
-                }
-                retryLoadLibrary = false;
-            }
-#ifdef QT_USE_MS_STD_EXCEPTION
-            else {
-                // An exception was thrown when calling qt_plugin_query_verification_data().
-                // This usually happens when plugin is compiled with the /clr compiler flag,
-                // & will only work if the dependencies are loaded & DLLMain() is called.
-                // LoadLibrary() will do this, try once with this & if it fails don't load.
-                retryLoadLibrary = !retryLoadLibrary;
-            }
-#endif
-#ifdef Q_OS_WIN
-            if (hTempModule) {
-                BOOL ok = ::FreeLibrary(hTempModule);
-                if (ok) {
-                    hTempModule = 0;
-                }
-
-            }
-#endif
-        } while (retryLoadLibrary);  // Will be 'false' in all cases other than when an
-        // exception is thrown(will happen only when using a MS compiler)
+        // scan for the plugin metadata without loading
+        success = findPatternUnloaded(fileName, this);
+    } else {
+        // library is already loaded (probably via QLibrary)
+        // simply get the target function and call it.
+        QtPluginQueryVerificationDataFunction getMetaData = NULL;
+        getMetaData = (QtPluginQueryVerificationDataFunction) resolve("qt_plugin_query_metadata");
+        success = qt_get_metadata(getMetaData, this);
     }
 
     if (!success) {