我有一个使用C++/Qt编写的应用程序,它使用QPluginLoader工具加载插件(.dll/.so)。该插件基本上是一个嵌入式Python解释器,允许通过PyQt4模块检查主应用程序中的Qt对象。
问题在于,从插入的Python解释器执行的命令PyQt4.QtCore.QCoreApplication.instance()返回None,即使QCoreApplication实例已由C++应用程序创建。
这只发生在Windows的调试模式下。
在Linux或Windows的发布模式下,PyQt4.QtCore.QCoreApplication.instance()命令将正确返回由C++应用程序创建的QCoreApplication实例。
以下是一些最小化的代码,显示了该问题。
在发布模式下编译时:
文件plugin.h
问题在于,从插入的Python解释器执行的命令PyQt4.QtCore.QCoreApplication.instance()返回None,即使QCoreApplication实例已由C++应用程序创建。
这只发生在Windows的调试模式下。
在Linux或Windows的发布模式下,PyQt4.QtCore.QCoreApplication.instance()命令将正确返回由C++应用程序创建的QCoreApplication实例。
以下是一些最小化的代码,显示了该问题。
在发布模式下编译时:
$ ./a.out
1+1
2
import PyQt4
import PyQt4.QtCore
PyQt4.QtCore.QCoreApplication.instance()
<PyQt4.QtCore.QCoreApplication object at 0x00C69198>
=> 好的
当调试模式编译时:
$ ./a.out
import PyQt4
import PyQt4.QtCore
PyQt4.QtCore.QCoreApplication.instance()
=> 不行(返回了None)
文件 main.cpp
#include <QCoreApplication>
#include <QPluginLoader>
#include <QDebug>
int main(int argc, char **argv)
{
QCoreApplication app(argc, argv);
QPluginLoader loader("plugin.dll");
loader.setLoadHints(QLibrary::ResolveAllSymbolsHint | QLibrary::ExportExternalSymbolsHint);
loader.load();
if(!loader.isLoaded()) {
qDebug() << loader.errorString();
return 1;
}
(void)loader.instance();
return app.exec();
}
文件plugin.h
#ifndef PLUGIN_H
#define PLUGIN_H
#include <QObject>
#include <Python.h>
class Plugin : public QObject
{
public:
Plugin();
~Plugin();
private:
PyThreadState *m_ts;
};
class InterpInput : public QObject
{
Q_OBJECT
public:
InterpInput(QObject *parent = 0) : QObject(parent) { }
public slots:
void monitorInput();
signals:
void done();
void inputReady();
};
class InterpOutput : public QObject
{
Q_OBJECT
public:
InterpOutput(QObject *parent = 0) : QObject(parent) { }
public slots:
void processLine();
public:
PyThreadState *m_ts;
};
#endif
文件 plugin.cpp
#include "plugin.h"
#include <QCoreApplication>
#include <QThread>
#include <QtPlugin>
#include <QPluginLoader>
Q_EXPORT_PLUGIN2(Plugin, Plugin)
Plugin::Plugin()
{
Py_Initialize();
PyEval_InitThreads();
InterpInput *in = new InterpInput();
InterpOutput *out = new InterpOutput(this);
in->connect(in, SIGNAL(inputReady()), out, SLOT(processLine()));
in->connect(in, SIGNAL(done()), QCoreApplication::instance(), SLOT(quit()));
QThread *thr = new QThread(this);
in->moveToThread(thr);
thr->connect(thr, SIGNAL(started()), in, SLOT(monitorInput()));
m_ts = PyEval_SaveThread();
out->m_ts = m_ts;
thr->start();
}
Plugin::~Plugin()
{
PyEval_RestoreThread(m_ts);
Py_Finalize();
}
void InterpInput::monitorInput()
{
PyGILState_STATE gstate;
gstate = PyGILState_Ensure();
int ret = PyRun_SimpleString("import sys\nimport code\nic = code.InteractiveConsole()");
assert(ret == 0);
while(true) {
ret = PyRun_SimpleString("line = ic.raw_input()");
if(ret) { break; }
inputReady();
}
done();
PyGILState_Release(gstate);
}
void InterpOutput::processLine()
{
PyEval_RestoreThread(m_ts);
int ret = PyRun_SimpleString("ic.push(line)");
PyRun_SimpleString("sys.stdout.flush()");
PyRun_SimpleString("sys.stderr.flush()");
(void)PyEval_SaveThread();
assert(ret == 0);
}
文件 Makefile
MOC=/cygdrive/c/Qt/4.8.4/bin/moc
GCC=/cygdrive/c/MinGW/bin/mingw32-g++.exe
FLAGS=-Ic:/Qt/4.8.4/include -Ic:/Qt/4.8.4/include/QtCore -Lc:/Qt/4.8.4/lib -Lc:/Qt/4.8.4/bin -lQtCore4 -Lc:/Python27/libs -lpython27 -Ic:/Python27/include -DQT_NO_DEBUG
#FLAGS=-Ic:/Qt/4.8.4/include -Ic:/Qt/4.8.4/include/QtCore -Lc:/Qt/4.8.4/bin -lQtCored4 -Lc:/Python27/libs -lpython27 -Ic:/Python27/include -g
LIBFLAGS=-shared
all:
$(MOC) plugin.h > plugin_moc.cpp
$(GCC) -o a.out main.cpp $(FLAGS)
$(GCC) -o plugin.dll $(LIBFLAGS) plugin.cpp plugin_moc.cpp $(FLAGS)