我正在使用Qt 5.11.1（MSVSC2015 32bit）和QtCreator 4.6.2。 我无法使用QXmlStreamReader解析XML。代码基于Qt's example编写。 执行我的代码时，它会在checkWarnMessage函数的QIODevice.cpp中产生访问冲突。 image显示呼叫堆栈和发生访问冲突的确切行。
实际的XML i更复杂，并且具有嵌套元素。解析XML的函数的实现方式与Qt示例中的void XbelReader :: readXBEL（）函数的实现方式相同（基于元素名称，调用了适当的函数来解析该元素）。但是通过这个简单的示例，我设法重现了实际解决方案中遇到的问题。
XML是：
<?xml version="1.0" encoding="UTF-8"?>
<root>
<element1>1</element1>
<element2>2</element2>
<element3>3</element3>
<element4>4</element4>
<element5>5</element5>
<element6>6</element6>
</root>
解析此XML的代码为：
#include <string>
#include <stdexcept>
#include <iostream>
#include <QCoreApplication>
#include <QXmlStreamReader>
#include <QFile>
#include <QString>
#define ASSERT_ELEMENT_NAME(NAME) Q_ASSERT(xmlReader.isStartElement() && xmlReader.name() == NAME);
using namespace std;
void OpenFile(const QString& fileName, QXmlStreamReader& xmlReader)
{
QFile configFile(fileName);
if (configFile.open(QFile::ReadOnly | QFile::Text) == false)
throw runtime_error(string("Failed to open file: ") + configFile.errorString().toStdString());
xmlReader.setDevice(&configFile);
if (xmlReader.readNextStartElement() == false)
throw runtime_error("File does not have root element");
if (xmlReader.name() != "root")
throw runtime_error("File has invalid root element");
}
void ParseElement1(QXmlStreamReader& xmlReader)
{
ASSERT_ELEMENT_NAME("element1");
auto text = xmlReader.readElementText().trimmed();
auto isOk = false;
auto value = text.toInt(&isOk);
if (isOk == false)
throw runtime_error(string("invalid value: ") + text.toStdString());
else
cout << "element1: " << value << endl;
}
void ParseElement2(QXmlStreamReader& xmlReader)
{
ASSERT_ELEMENT_NAME("element2");
auto text = xmlReader.readElementText().trimmed();
auto isOk = false;
auto value = text.toInt(&isOk);
if (isOk == false)
throw runtime_error(string("invalid value: ") + text.toStdString());
else
cout << "element2: " << value << endl;
}
int main()
{
QXmlStreamReader xmlReader;
OpenFile("config.xml", xmlReader);
while(xmlReader.readNextStartElement())
{
if(xmlReader.name() == "element1")
ParseElement1(xmlReader);
if(xmlReader.name() == "element2")
ParseElement2(xmlReader);
else
xmlReader.skipCurrentElement();
}
}
如果我在主函数中注释了两行：
if(xmlReader.name() == "element2")
ParseElement2(xmlReader);
不会发生访问冲突。
我真的不知道我在做什么错。还是QXmlStreamReader中存在错误？我认为，即使我做错了什么，也不应在Qt的库中发生访问冲突。
可以从此link
下载整个项目（XmlParser.pro，main.cpp和config.xml）。编辑
我已按照曼森（Manthan）的建议修正了自己的例子，该例子按预期工作。我向XML添加了另一件事。我在element1之前添加了大的多行注释。注释本身有8019个字符，包括空格字符，而整个XML文件有8266个字符。
XML现在看起来像
<?xml version="1.0" encoding="UTF-8"?>
<root>
<!--
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-->
<element1>1</element1>
<element2>2</element2>
<element3>3</element3>
<element4>4</element4>
<element5>5</element5>
<element6>6</element6>
</root>
我已经使用XML Tools插件在Notepad ++中以及xmlvalidation.xml上检查了XML是否有效。当我使用新的XML执行固定的示例时，再次在先前链接的图像上所描绘的完全相同的地方出现访问冲突。
现在，如果我从XML的注释中删除最后一个“ o”字符（或从注释中删除任何其他字符，或者例如从element6的文本中删除“ 6”，或者事实上从XML中的任何字符保持XML有效） ，示例成功执行。这是我最初的问题。我的原始XML文件中有很多注释，导致文件大于8KB。目前，作为一种解决方法，我删除了注释以避免访问冲突。
我不清楚注释（或文件）长度如何导致访问冲突。
可以从此link
下载整个项目答案 0 :(得分：4)
问题在while循环内。如下更新。
while(xmlReader.readNextStartElement())
{
if(xmlReader.name() == "element1")
ParseElement1(xmlReader);
else if(xmlReader.name() == "element2")
ParseElement2(xmlReader);
else
xmlReader.skipCurrentElement();
}
在您的代码中，第一个元素的类型为'element1'，然后首先对其进行处理（使用第一个if），然后它们再次到达else，在此处尝试跳过该元素，从而导致问题。