I am trying to create a basic performance profiler for QtScript using the QScriptEngineAgent in order to capture function entries and exits. I have successfully set up the callback for
QScriptEngineAgent::functionEntry()Although I understand that not all script functions necessarily have names, even in simple cases it doesn't seem to be working. Despite attempts with QScriptContextInfo, it does not provide the function name. Trying to access arguments.callee.name also failed.
Below is an outline of my implementation attempts, which I am testing on qt-5.3.2/linux.
tmp.pro:
TEMPLATE = app
TARGET = tmp
INCLUDEPATH += .
QT += core script
SOURCES += main.cpp
main.cpp:
#include <QCoreApplication>
#include <QScriptEngine>
#include <QScriptEngineAgent>
#include <QScriptContextInfo>
#include <QDebug>
class MyAgent: public QScriptEngineAgent {
private:
void functionEntry(qint64 scriptId) {
qDebug() << "functionEntry" << scriptId;
QScriptContext *context = engine()->currentContext();
// Attempting to retrieve the function name from context info
QScriptContextInfo contextInfo(context);
qDebug() << contextInfo.functionName();
// Trying to access the function name through arguments.callee.name
QScriptValue callee = context->callee();
qDebug() << callee.property("name").toString();
// Checking if function.toString() provides any useful information
qDebug() << callee.toString();
// Printing out details of the current context
qDebug() << context->toString();
}
public:
MyAgent(QScriptEngine *eng) : QScriptEngineAgent(eng) {
qDebug() << "engine" << eng;
}
};
int main(int argc, char **argv) {
QCoreApplication app(argc, argv);
QScriptEngine eng;
MyAgent agent(&eng);
eng.setAgent(&agent);
qDebug() << "agent " << eng.agent();
eng.evaluate("function foo() { return 6 * 7; }"
"function bar() { return foo(); }");
QScriptValue bar = eng.globalObject().property("bar");
// Confirming that callee is printed correctly here
qDebug() << "call " << bar.property("name").toString() << bar.toString();
QScriptValue ret = bar.call();
qDebug() << "answer" << ret.toNumber();
return 0;
}
This is a sample of the output, which does not meet my expectations as I would like to see "foo" and "bar" instead of empty strings:
engine QScriptEngine(0x7fffc55c4560)
agent 0x7fffc55c4570
functionEntry 140300485581200
""
""
""
"<global>() at -1"
functionEntry -1
""
""
""
"<global>() at -1"
call "bar" "function bar() { return foo(); }"
functionEntry 140300485581200
""
""
""
"<global>() at -1"
functionEntry 140300485581200
""
""
""
"<global>() at -1"
answer 42