Try to load QML cache from CacheLocation if side-by-side fails

This could happen if the .qmlc file is stale or corrupt for some reason.
In that case, we should try to load a cache file from the user's
CacheLocation.

Change-Id: Id2be776c7ae0467c9d9ffffd1543204272a531d1
Reviewed-by: Simon Hausmann <simon.hausmann@qt.io>

5 files changed, 82 insertions, 21 deletions

diff --git a/src/qml/compiler/qv4compileddata.cpp b/src/qml/compiler/qv4compileddata.cpp
index 02aee47eea..0c81a5b3c6 100644
--- a/src/qml/compiler/qv4compileddata.cpp
+++ b/src/qml/compiler/qv4compileddata.cpp
@@ -76,7 +76,18 @@ namespace QV4 {
 
 namespace CompiledData {
 
+#if defined(QML_COMPILE_HASH)
+#  ifdef Q_OS_LINUX
+// Place on a separate section on Linux so it's easier to check from outside
+// what the hash version is.
+__attribute__((section(".qml_compile_hash")))
+#  endif
+const char qml_compile_hash[48 + 1] = QML_COMPILE_HASH;
 static_assert(sizeof(Unit::libraryVersionHash) >= QML_COMPILE_HASH_LENGTH + 1, "Compile hash length exceeds reserved size in data structure. Please adjust and bump the format version");
+#else
+#  error "QML_COMPILE_HASH must be defined for the build of QtDeclarative to ensure version checking for cache files"
+#endif
+
 
 CompilationUnit::CompilationUnit(const Unit *unitData)
 {
@@ -351,26 +362,27 @@ bool CompilationUnit::loadFromDisk(const QUrl &url, const QDateTime &sourceTimeS
     const QString sourcePath = QQmlFile::urlToLocalFileOrQrc(url);
     QScopedPointer<CompilationUnitMapper> cacheFile(new CompilationUnitMapper());
 
-    QString cachePath = sourcePath + QLatin1Char('c');
-    if (!QFile::exists(cachePath))
-        cachePath = localCacheFilePath(url);
+    const QStringList cachePaths = { sourcePath + QLatin1Char('c'), localCacheFilePath(url) };
+    for (const QString &cachePath : cachePaths) {
+        CompiledData::Unit *mappedUnit = cacheFile->open(cachePath, sourceTimeStamp, errorString);
+        if (!mappedUnit)
+            continue;
 
-    CompiledData::Unit *mappedUnit = cacheFile->open(cachePath, sourceTimeStamp, errorString);
-    if (!mappedUnit)
-        return false;
+        const Unit * const oldDataPtr = (data && !(data->flags & QV4::CompiledData::Unit::StaticData)) ? data : nullptr;
+        QScopedValueRollback<const Unit *> dataPtrChange(data, mappedUnit);
 
-    const Unit * const oldDataPtr = (data && !(data->flags & QV4::CompiledData::Unit::StaticData)) ? data : nullptr;
-    QScopedValueRollback<const Unit *> dataPtrChange(data, mappedUnit);
+        if (data->sourceFileIndex != 0 && sourcePath != QQmlFile::urlToLocalFileOrQrc(stringAt(data->sourceFileIndex))) {
+            *errorString = QStringLiteral("QML source file has moved to a different location.");
+            continue;
+        }
 
-    if (data->sourceFileIndex != 0 && sourcePath != QQmlFile::urlToLocalFileOrQrc(stringAt(data->sourceFileIndex))) {
-        *errorString = QStringLiteral("QML source file has moved to a different location.");
-        return false;
+        dataPtrChange.commit();
+        free(const_cast<Unit*>(oldDataPtr));
+        backingFile.reset(cacheFile.take());
+        return true;
     }
 
-    dataPtrChange.commit();
-    free(const_cast<Unit*>(oldDataPtr));
-    backingFile.reset(cacheFile.take());
-    return true;
+    return false;
 }
 
 void CompilationUnit::linkBackendToEngine(ExecutionEngine *engine)
@@ -783,7 +795,7 @@ bool Unit::verifyHeader(QDateTime expectedSourceTimeStamp, QString *errorString)
     }
 
 #if defined(QML_COMPILE_HASH)
-    if (qstrcmp(QML_COMPILE_HASH, libraryVersionHash) != 0) {
+    if (qstrcmp(CompiledData::qml_compile_hash, libraryVersionHash) != 0) {
         *errorString = QStringLiteral("QML library version mismatch. Expected compile hash does not match");
         return false;
     }
diff --git a/src/qml/compiler/qv4compileddata_p.h b/src/qml/compiler/qv4compileddata_p.h
index c1be00ea27..0ac40d2800 100644
--- a/src/qml/compiler/qv4compileddata_p.h
+++ b/src/qml/compiler/qv4compileddata_p.h
@@ -752,7 +752,9 @@ struct Import
 };
 static_assert(sizeof(Import) == 24, "Import structure needs to have the expected size to be binary compatible on disk when generated by host compiler and loaded by target");
 
+enum { QmlCompileHashSpace = 48 };
 static const char magic_str[] = "qv4cdata";
+extern const char qml_compile_hash[QmlCompileHashSpace + 1];
 
 struct Unit
 {
@@ -764,7 +766,7 @@ struct Unit
     quint32_le unitSize; // Size of the Unit and any depending data.
     // END DO NOT CHANGE THESE FIELDS EVER
 
-    char libraryVersionHash[48];
+    char libraryVersionHash[QmlCompileHashSpace];
 
     char md5Checksum[16]; // checksum of all bytes following this field.
     void generateChecksum();
diff --git a/src/qml/compiler/qv4compiler.cpp b/src/qml/compiler/qv4compiler.cpp
index f1afad4965..76779fece8 100644
--- a/src/qml/compiler/qv4compiler.cpp
+++ b/src/qml/compiler/qv4compiler.cpp
@@ -48,9 +48,6 @@
 #include <wtf/MathExtras.h>
 #include <QCryptographicHash>
 
-// generated by qmake:
-#include "qml_compile_hash_p.h"
-
 QV4::Compiler::StringTableGenerator::StringTableGenerator()
 {
     clear();
@@ -482,7 +479,7 @@ QV4::CompiledData::Unit QV4::Compiler::JSUnitGenerator::generateHeader(QV4::Comp
     unit.flags |= module->unitFlags;
     unit.version = QV4_DATA_STRUCTURE_VERSION;
     unit.qtVersion = QT_VERSION;
-    qstrcpy(unit.libraryVersionHash, QML_COMPILE_HASH);
+    qstrcpy(unit.libraryVersionHash, CompiledData::qml_compile_hash);
     memset(unit.md5Checksum, 0, sizeof(unit.md5Checksum));
     memset(unit.dependencyMD5Checksum, 0, sizeof(unit.dependencyMD5Checksum));
 
diff --git a/tests/auto/qml/qmlcachegen/tst_qmlcachegen.cpp b/tests/auto/qml/qmlcachegen/tst_qmlcachegen.cpp
index 48eb694167..60717dfafa 100644
--- a/tests/auto/qml/qmlcachegen/tst_qmlcachegen.cpp
+++ b/tests/auto/qml/qmlcachegen/tst_qmlcachegen.cpp
@@ -32,6 +32,7 @@
 #include <QQmlEngine>
 #include <QProcess>
 #include <QLibraryInfo>
+#include <QStandardPaths>
 #include <QSysInfo>
 #include <QLoggingCategory>
 #include <private/qqmlcomponent_p.h>
@@ -105,6 +106,13 @@ static bool generateCache(const QString &qmlFileName, QByteArray *capturedStderr
 void tst_qmlcachegen::initTestCase()
 {
     qputenv("QML_FORCE_DISK_CACHE", "1");
+    QStandardPaths::setTestModeEnabled(true);
+
+    // make sure there's no pre-existing cache dir
+    QString cacheDir = QStandardPaths::writableLocation(QStandardPaths::CacheLocation);
+    if (!cacheDir.isEmpty())
+        //QDir(cacheDir).removeRecursively();
+        qDebug() << cacheDir;
 }
 
 void tst_qmlcachegen::loadGeneratedFile()
diff --git a/tests/auto/qml/qmldiskcache/tst_qmldiskcache.cpp b/tests/auto/qml/qmldiskcache/tst_qmldiskcache.cpp
index d363180c06..284a324227 100644
--- a/tests/auto/qml/qmldiskcache/tst_qmldiskcache.cpp
+++ b/tests/auto/qml/qmldiskcache/tst_qmldiskcache.cpp
@@ -48,6 +48,7 @@ class tst_qmldiskcache: public QObject
 private slots:
     void initTestCase();
 
+    void loadLocalAsFallback();
     void regenerateAfterChange();
     void registerImportForImplicitComponent();
     void basicVersionChecks();
@@ -204,6 +205,47 @@ struct TestCompiler
 void tst_qmldiskcache::initTestCase()
 {
     qputenv("QML_FORCE_DISK_CACHE", "1");
+    QStandardPaths::setTestModeEnabled(true);
+}
+
+void tst_qmldiskcache::loadLocalAsFallback()
+{
+    QQmlEngine engine;
+    TestCompiler testCompiler(&engine);
+
+    QVERIFY(testCompiler.tempDir.isValid());
+
+    const QByteArray contents = QByteArrayLiteral("import QtQml 2.0\n"
+                                                  "QtObject {\n"
+                                                   "    property string blah: Qt.platform;\n"
+                                                   "}");
+
+    QVERIFY2(testCompiler.compile(contents), qPrintable(testCompiler.lastErrorString));
+
+    // Create an invalid side-by-side .qmlc
+    {
+        QFile f(testCompiler.tempDir.path() + "/test.qmlc");
+        QVERIFY(f.open(QIODevice::WriteOnly | QIODevice::Truncate));
+        QV4::CompiledData::Unit unit = {};
+        memcpy(unit.magic, QV4::CompiledData::magic_str, sizeof(unit.magic));
+        unit.version = QV4_DATA_STRUCTURE_VERSION;
+        unit.qtVersion = QT_VERSION;
+        unit.sourceTimeStamp = testCompiler.mappedFile.fileTime(QFile::FileModificationTime).toMSecsSinceEpoch();
+        unit.unitSize = ~0U;    // make the size a silly number
+        // write something to the library hash that should cause it not to be loaded
+        memset(unit.libraryVersionHash, 'z', sizeof(unit.libraryVersionHash));
+        memset(unit.md5Checksum, 0, sizeof(unit.md5Checksum));
+
+        // leave the other fields unset, since they don't matter
+
+        f.write(reinterpret_cast<const char *>(&unit), sizeof(unit));
+    }
+
+    QQmlRefPointer<QV4::CompiledData::CompilationUnit> unit = QV4::Compiler::Codegen::createUnitForLoading();
+    bool loaded = unit->loadFromDisk(QUrl::fromLocalFile(testCompiler.testFilePath), QFileInfo(testCompiler.testFilePath).lastModified(),
+                                     &testCompiler.lastErrorString);
+    QVERIFY2(loaded, qPrintable(testCompiler.lastErrorString));
+    QCOMPARE(unit->objectCount(), 1);
 }
 
 void tst_qmldiskcache::regenerateAfterChange()