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。代码是基于Qt 的示例编写的。当我的代码被执行时，它会在 checkWarnMessage 函数的 QIODevice.cpp 中产生访问冲突。此图像显示调用堆栈和发生访问冲突的确切行。
实际的 XML 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() 函数相同（根据元素名称调用适当的函数来解析该元素）。但是通过这个简单的例子，我设法重现了我在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 的代码是：
#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两行：
if(xmlReader.name() == "element2")
ParseElement2(xmlReader);
不会发生访问冲突。
我真的不知道我做错了什么。或者 QXmlStreamReader 中是否存在错误？我认为即使我做错了什么，Qt 的库中也不应该发生访问冲突。
可以从此链接下载整个项目（XmlParser.pro、main.cpp 和 config.xml）
编辑
我已经按照 Manthan 的建议修复了我的示例，并且它按预期工作。我在 XML 中又添加了一件东西。我在 element1 之前添加了大的多行注释。注释本身有 8019 个字符，包括空白字符，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>
我检查了 XML 在带有 XML 工具插件的 Notepad++ 以及 xmlvalidation.xml 中是否有效。当我使用新的 XML 执行固定示例时，我再次在先前链接的图像上描述的完全相同的位置发生访问冲突。
现在，如果我从 XML 中的注释中删除最后一个“o”字符（或注释中的任何其他字符，或者例如 element6 的文本中的“6”，或者事实上，在保持 XML 有效的情况下来自 XML 的任何字符），示例是成功执行。这是我原来的问题。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，我删除评论以避免访问冲突。
我不清楚评论（或文件）长度如何导致访问冲突。
整个项目可以从此链接下载