Fail to generate a triangle by openGL(Qt5.0.2)

[stereoMatching]

OS : mac osx 10.8.3
compiler : clang3.2

I am a beginner of opengl, trying to play opengl with Qt5

There are two problems about this simple program(plot a triangle)
1 : I can't see the triangle
2 : The program could not exit even I close the window

hpp

#ifndef CH1HELLOTRIANGLE_HPP
#define CH1HELLOTRIANGLE_HPP
 
#include <QGLWidget>
 
#include <QtGui/QOpenGLFunctions>
#include <QtGui/QOpenGLShaderProgram>
 
class QWidget;
 
class ch1HelloTriangle : public QGLWidget, protected QOpenGLFunctions
{
    Q_OBJECT
public:
    explicit ch1HelloTriangle(QWidget *parent = 0);
 
protected:
    virtual void initializeGL();
    void initShaders();
    void InitializeVertexBuffer();
 
    virtual void resizeGL(int w, int h);
    virtual void paintGL();
 
private:
    QOpenGLShaderProgram program;
 
    GLuint positionBufferObject;
};
 
#endif // CH1HELLOTRIANGLE_HPP

#ifndef CH1HELLOTRIANGLE_HPP
#define CH1HELLOTRIANGLE_HPP

#include <QGLWidget>

#include <QtGui/QOpenGLFunctions>
#include <QtGui/QOpenGLShaderProgram>

class QWidget;

class ch1HelloTriangle : public QGLWidget, protected QOpenGLFunctions
{
    Q_OBJECT
public:
    explicit ch1HelloTriangle(QWidget *parent = 0);

protected:
    virtual void initializeGL();
    void initShaders();
    void InitializeVertexBuffer();

    virtual void resizeGL(int w, int h);
    virtual void paintGL();
    
private:
    QOpenGLShaderProgram program;

    GLuint positionBufferObject;
};

#endif // CH1HELLOTRIANGLE_HPP

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.cpp

#include <locale.h>
 
#include <QWidget>
 
#include "ch1HelloTriangle.hpp"
 
namespace
{
 
float const vertexPositions[] = {
    0.75f,  0.75f, 0.0f, 1.0f,
    0.75f, -0.75f, 0.0f, 1.0f,
    -0.75f, -0.75f, 0.0f, 1.0f,
};
 
}
 
ch1HelloTriangle::ch1HelloTriangle(QWidget *parent) :
    QGLWidget(parent)
{
}
 
void ch1HelloTriangle::initializeGL()
{
    initializeOpenGLFunctions();
    InitializeVertexBuffer();
    initShaders();
}
 
void ch1HelloTriangle::initShaders()
{
    // Override system locale until shaders are compiled
    setlocale(LC_NUMERIC, "C");
 
    // Compile vertex shader
    if (!program.addShaderFromSourceCode(QOpenGLShader::Vertex,
                                         "attribute vec4 position;\n"
                                         "void main()\n"
                                         "{\n"
                                         "   gl_Position = position;\n"
                                         "}\n"))
    {
        close();
    }
 
    // Compile fragment shader
    if (!program.addShaderFromSourceCode(QOpenGLShader::Fragment,
                                         "out vec4 outputColor;\n"
                                         "void main()\n"
                                         "{\n"
                                         "   outputColor = vec4(1.0f, 1.0f, 1.0f, 1.0f);\n"
                                         "}\n"))
    {
        close();
 
    }
 
    // Link shader pipeline
    if (!program.link())
        close();
 
    // Bind shader pipeline for use
    if (!program.bind())
        close();
 
    // Restore system locale
    setlocale(LC_ALL, "");
}
 
void ch1HelloTriangle::InitializeVertexBuffer()
{
    glGenBuffers(1, &positionBufferObject);
 
    glBindBuffer(GL_ARRAY_BUFFER, positionBufferObject);
    glBufferData(GL_ARRAY_BUFFER, sizeof(vertexPositions), vertexPositions, GL_STATIC_DRAW);
    glBindBuffer(GL_ARRAY_BUFFER, 0);
}
 
void ch1HelloTriangle::resizeGL(int w, int h)
{
    // Set OpenGL viewport to cover whole widget
    glViewport(0, 0, w, h);
}
 
void ch1HelloTriangle::paintGL()
{
    glClearColor(0.0f, 0.0f, 0.0f, 0.0f);
    glClear(GL_COLOR_BUFFER_BIT);
 
    glBindBuffer(GL_ARRAY_BUFFER, positionBufferObject);
 
    int vertexLocation = program.attributeLocation("position");
    program.enableAttributeArray(vertexLocation);
 
    glVertexAttribPointer(vertexLocation, 4, GL_FLOAT, GL_FALSE, 0, 0);
 
    glDrawArrays(GL_TRIANGLES, 0, 3);    
}

#include <locale.h>

#include <QWidget>

#include "ch1HelloTriangle.hpp"

namespace
{

float const vertexPositions[] = {
    0.75f,  0.75f, 0.0f, 1.0f,
    0.75f, -0.75f, 0.0f, 1.0f,
    -0.75f, -0.75f, 0.0f, 1.0f,
};

}

ch1HelloTriangle::ch1HelloTriangle(QWidget *parent) :
    QGLWidget(parent)
{
}

void ch1HelloTriangle::initializeGL()
{
    initializeOpenGLFunctions();
    InitializeVertexBuffer();
    initShaders();
}

void ch1HelloTriangle::initShaders()
{
    // Override system locale until shaders are compiled
    setlocale(LC_NUMERIC, "C");

    // Compile vertex shader
    if (!program.addShaderFromSourceCode(QOpenGLShader::Vertex,
                                         "attribute vec4 position;\n"
                                         "void main()\n"
                                         "{\n"
                                         "   gl_Position = position;\n"
                                         "}\n"))
    {
        close();
    }

    // Compile fragment shader
    if (!program.addShaderFromSourceCode(QOpenGLShader::Fragment,
                                         "out vec4 outputColor;\n"
                                         "void main()\n"
                                         "{\n"
                                         "   outputColor = vec4(1.0f, 1.0f, 1.0f, 1.0f);\n"
                                         "}\n"))
    {
        close();

    }

    // Link shader pipeline
    if (!program.link())
        close();

    // Bind shader pipeline for use
    if (!program.bind())
        close();

    // Restore system locale
    setlocale(LC_ALL, "");
}

void ch1HelloTriangle::InitializeVertexBuffer()
{
    glGenBuffers(1, &positionBufferObject);

    glBindBuffer(GL_ARRAY_BUFFER, positionBufferObject);
    glBufferData(GL_ARRAY_BUFFER, sizeof(vertexPositions), vertexPositions, GL_STATIC_DRAW);
    glBindBuffer(GL_ARRAY_BUFFER, 0);
}

void ch1HelloTriangle::resizeGL(int w, int h)
{
    // Set OpenGL viewport to cover whole widget
    glViewport(0, 0, w, h);
}

void ch1HelloTriangle::paintGL()
{
    glClearColor(0.0f, 0.0f, 0.0f, 0.0f);
    glClear(GL_COLOR_BUFFER_BIT);

    glBindBuffer(GL_ARRAY_BUFFER, positionBufferObject);
   
    int vertexLocation = program.attributeLocation("position");
    program.enableAttributeArray(vertexLocation);
    
    glVertexAttribPointer(vertexLocation, 4, GL_FLOAT, GL_FALSE, 0, 0);

    glDrawArrays(GL_TRIANGLES, 0, 3);    
}

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main.cpp

#include <QApplication>
 
#include "ch1HelloTriangle.hpp"
 
int main(int argc, char *argv[])
{
    QApplication a(argc, argv);
 
    ch1HelloTriangle ch1;
    ch1.show();
 
    return a.exec(&#41;;
}

#include <QApplication>

#include "ch1HelloTriangle.hpp"

int main(int argc, char *argv[])
{
    QApplication a(argc, argv);

    ch1HelloTriangle ch1;
    ch1.show();
    
    return a.exec(&#41;;
}

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