Forward declare all types required for compilation with `-trace`

This patch fixes compilation with `-trace lttng` or `-trace etw`. We
need to forward declare QEvent, QImageReader etc., otherwise the types
will be unknown while compiling the trace points.

In order to handle this generically, the tracegen utility is extended
to support a 'prefix text' in the `*.tracepoints` input files. Any
text within curly braces will be embedded as-is in the generated file.
This can then be used to add forward declarations for the types we
need, including potential namespaces and such.

Change-Id: I5cb16763ce0fcb48ce3ea4577578d468ff3a4f4b
Reviewed-by: Konstantin Tokarev <annulen@yandex.ru>

7 files changed, 65 insertions, 17 deletions

diff --git a/src/corelib/qtcore.tracepoints b/src/corelib/qtcore.tracepoints
index 33734a4274..a9a08071f3 100644
--- a/src/corelib/qtcore.tracepoints
+++ b/src/corelib/qtcore.tracepoints
@@ -1,3 +1,9 @@
+{
+QT_BEGIN_NAMESPACE
+class QEvent;
+QT_END_NAMESPACE
+}
+
 QCoreApplicationPrivate_init_entry()
 QCoreApplicationPrivate_init_exit()
 
diff --git a/src/gui/qtgui.tracepoints b/src/gui/qtgui.tracepoints
index aed6c35c03..0a96a589b1 100644
--- a/src/gui/qtgui.tracepoints
+++ b/src/gui/qtgui.tracepoints
@@ -1,3 +1,9 @@
+{
+QT_BEGIN_NAMESPACE
+class QImageReader;
+QT_END_NAMESPACE
+}
+
 QGuiApplicationPrivate_init_entry()
 QGuiApplicationPrivate_init_exit()
 
diff --git a/src/tools/tracegen/etw.cpp b/src/tools/tracegen/etw.cpp
index 8c065f93c9..e839137915 100644
--- a/src/tools/tracegen/etw.cpp
+++ b/src/tools/tracegen/etw.cpp
@@ -110,19 +110,21 @@ static QString createGuid(const QUuid &uuid)
     return guid;
 }
 
-static void writePrologue(QTextStream &stream, const QString &fileName, const QString &providerName)
+static void writePrologue(QTextStream &stream, const QString &fileName, const Provider &provider)
 {
-    QUuid uuid = QUuid::createUuidV5(QUuid(), providerName.toLocal8Bit());
+    QUuid uuid = QUuid::createUuidV5(QUuid(), provider.name.toLocal8Bit());
 
-    const QString provider = providerVar(providerName);
+    const QString providerV = providerVar(provider.name);
     const QString guard = includeGuard(fileName);
     const QString guid = createGuid(uuid);
     const QString guidString = uuid.toString();
 
     stream << "#ifndef " << guard << "\n"
            << "#define " << guard << "\n"
+           << "\n"
            << "#include <windows.h>\n"
-           << "#include <TraceLoggingProvider.h>\n";
+           << "#include <TraceLoggingProvider.h>\n"
+           << "\n";
 
     /* TraceLogging API macros cannot deal with UTF8
      * source files, so we work around it like this
@@ -132,30 +134,33 @@ static void writePrologue(QTextStream &stream, const QString &fileName, const QS
               "#define _TlgPragmaUtf8Begin\n"
               "#define _TlgPragmaUtf8End\n";
 
+    stream << "\n";
     stream << qtHeaders();
-
     stream << "\n";
 
+    if (!provider.prefixText.isEmpty())
+        stream << provider.prefixText.join(QLatin1Char('\n')) << "\n\n";
+
     stream << "#ifdef TRACEPOINT_DEFINE\n"
            << "/* " << guidString << " */\n"
-           << "TRACELOGGING_DEFINE_PROVIDER(" << provider << ", \""
-           << providerName <<"\", " << guid << ");\n\n";
+           << "TRACELOGGING_DEFINE_PROVIDER(" << providerV << ", \""
+           << provider.name <<"\", " << guid << ");\n\n";
 
     stream << "static inline void registerProvider()\n"
            << "{\n"
-           << "    TraceLoggingRegister(" << provider << ");\n"
+           << "    TraceLoggingRegister(" << providerV << ");\n"
            << "}\n\n";
 
     stream << "static inline void unregisterProvider()\n"
            << "{\n"
-           << "    TraceLoggingUnregister(" << provider << ");\n"
+           << "    TraceLoggingUnregister(" << providerV << ");\n"
            << "}\n";
 
     stream << "Q_CONSTRUCTOR_FUNCTION(registerProvider)\n"
            << "Q_DESTRUCTOR_FUNCTION(unregisterProvider)\n\n";
 
     stream << "#else\n"
-           << "TRACELOGGING_DECLARE_PROVIDER(" << provider << ");\n"
+           << "TRACELOGGING_DECLARE_PROVIDER(" << providerV << ");\n"
            << "#endif // TRACEPOINT_DEFINE\n\n";
 }
 
@@ -224,7 +229,7 @@ void writeEtw(QFile &file, const Provider &provider)
 
     const QString fileName = QFileInfo(file.fileName()).fileName();
 
-    writePrologue(stream, fileName, provider.name);
+    writePrologue(stream, fileName, provider);
     writeTracepoints(stream, provider);
     writeEpilogue(stream, fileName);
 }
diff --git a/src/tools/tracegen/lttng.cpp b/src/tools/tracegen/lttng.cpp
index 5d41bf5f1f..f0fbca9e16 100644
--- a/src/tools/tracegen/lttng.cpp
+++ b/src/tools/tracegen/lttng.cpp
@@ -104,16 +104,21 @@ static void writeCtfMacro(QTextStream &stream, const Tracepoint::Field &field)
     }
 }
 
-static void writePrologue(QTextStream &stream, const QString &fileName, const QString &providerName)
+static void writePrologue(QTextStream &stream, const QString &fileName, const Provider &provider)
 {
+    const QString guard = includeGuard(fileName);
+
     stream << "#undef TRACEPOINT_PROVIDER\n";
-    stream << "#define TRACEPOINT_PROVIDER " << providerName << "\n\n";
+    stream << "#define TRACEPOINT_PROVIDER " << provider.name << "\n";
+    stream << "\n";
 
+    // include prefix text or qt headers only once
+    stream << "#if !defined(" << guard << ")\n";
     stream << qtHeaders();
-
-    const QString guard = includeGuard(fileName);
-
     stream << "\n";
+    if (!provider.prefixText.isEmpty())
+        stream << provider.prefixText.join(QLatin1Char('\n')) << "\n\n";
+    stream << "#endif\n\n";
 
     /* the first guard is the usual one, the second is required
      * by LTTNG to force the re-evaluation of TRACEPOINT_* macros
@@ -213,7 +218,7 @@ void writeLttng(QFile &file, const Provider &provider)
 
     const QString fileName = QFileInfo(file.fileName()).fileName();
 
-    writePrologue(stream, fileName, provider.name);
+    writePrologue(stream, fileName, provider);
     writeTracepoints(stream, provider);
     writeEpilogue(stream, fileName);
 }
diff --git a/src/tools/tracegen/provider.cpp b/src/tools/tracegen/provider.cpp
index a6523a2e3d..39633efe5d 100644
--- a/src/tools/tracegen/provider.cpp
+++ b/src/tools/tracegen/provider.cpp
@@ -275,9 +275,21 @@ Provider parseProvider(const QString &filename)
     Provider provider;
     provider.name = QFileInfo(filename).baseName();
 
+    bool parsingPrefixText = false;
     for (int lineNumber = 1; !s.atEnd(); ++lineNumber) {
         QString line = s.readLine().trimmed();
 
+        if (line == QLatin1String("{")) {
+            parsingPrefixText = true;
+            continue;
+        } else if (parsingPrefixText && line == QLatin1String("}")) {
+            parsingPrefixText = false;
+            continue;
+        } else if (parsingPrefixText) {
+            provider.prefixText.append(line);
+            continue;
+        }
+
         if (line.isEmpty() || line.startsWith(QLatin1Char('#')))
             continue;
 
@@ -296,7 +308,14 @@ Provider parseProvider(const QString &filename)
         }
     }
 
+    if (parsingPrefixText) {
+        panic("Syntax error while processing '%s': "
+              "no closing brace found for prefix text block",
+              qPrintable(filename));
+    }
+
 #ifdef TRACEGEN_DEBUG
+    qDebug() << provider.prefixText;
     for (auto i = provider.tracepoints.constBegin(); i != provider.tracepoints.constEnd(); ++i)
         dumpTracepoint(*i);
 #endif
diff --git a/src/tools/tracegen/provider.h b/src/tools/tracegen/provider.h
index 9771e62f4d..9be0c33d89 100644
--- a/src/tools/tracegen/provider.h
+++ b/src/tools/tracegen/provider.h
@@ -86,6 +86,7 @@ struct Provider
 {
     QString name;
     QVector<Tracepoint> tracepoints;
+    QStringList prefixText;
 };
 
 Provider parseProvider(const QString &filename);
diff --git a/src/widgets/qtwidgets.tracepoints b/src/widgets/qtwidgets.tracepoints
index 01a1383670..bfaf87ffcc 100644
--- a/src/widgets/qtwidgets.tracepoints
+++ b/src/widgets/qtwidgets.tracepoints
@@ -1,3 +1,9 @@
+{
+QT_BEGIN_NAMESPACE
+class QEvent;
+QT_END_NAMESPACE
+}
+
 QApplication_notify_entry(QObject *receiver, QEvent *event, int type)
 QApplication_notify_event_filtered(QObject *receiver, QEvent *event, int type)
 QApplication_notify_before_delivery(QObject *receiver, QEvent *event, int type)