地址读取xml时超出范围错误

问题描述

在使用libxml解析文件时，我遇到了一个奇怪的错误。此代码在我将其编译为32位应用程序时工作。我改变它为一个64位的应用程序，它停止工作。

seg错误发生在if（xmlStrcmp（cur-> name，（const xmlChar *）服务器））

cur-> name是一个const xmlChar *，它指向一个地址，它说出它的出界。但是当我调试并去那个内存位置时，数据是正确的。

  int XmlGetServers（）
 {
 xmlDocPtr doc; 
 xmlNodePtr cur; 
 
 DOC = xmlParseFile（Pin.xml）; 
 if（doc == NULL）
 {
 std :: cout<< \\\
 Pin.xml未成功解析。 << std :: endl; 
 return -1; 
} 
 cur = xmlDocGetRootElement（doc）; 
 
 if（cur == NULL）
 {
 std :: cout< \\\
 Pin.xml是空文档。 << std :: endl; 
 xmlFreeDoc（doc）; 
 return -1; 
} 
 if（xmlStrcmp（cur-> name，（const xmlChar *）servers））
 {
 std :: cout< \\\
 ERROR：Pin.xml的类型错误，根节点！= servers。 << std :: endl; 
 xmlFreeDoc（doc）; 
 return -1; 
} 
} 
  

在cur初始化之前，name参数为

 名称：name 
详细信息：0xed11f72000007fff< Address 0xed11f72000007fff out of bounds> 
 

cur初始化后，name参数为

 名称：name 
详细信息：0x64c43000000000<地址0x64c43000000000超出范围> 
  

引用的XML文件

 <？xml version =1.0？> 
 
< servers> 
 
< server_info> 
 
< server_name> Server1< / server_name> 
 
< server_ip> 127.0.0.1< / server_ip> 
 
< server_data_port> 9000< / server_data_port> 
 
< / server_info> 
 
< server_info> 
 
< server_name> Server2< / server_name> 
 
< server_ip> 127.0.0.1< / server_ip> 
 
< server_data_port> 9001< / server_data_port> 
 
< / server_info> 
 
< / servers> 
  

系统：

操作系统：Redhat Enterprise Linux 6.4 64位

GCC：4.4.7-3

包：libxml2-2.7.6- 8.el6_3.4.x86_64

解决方案

问题是我们在代码中使用#pragma pack $ b意味着DOMParser中的bool被压缩到1个字节，而Xerces不会#pragma pack并且得到4个字节的默认包装。

I am getting a weird segfault when using libxml to parse a file. This code worked previously when I compiled it as a 32bit application. I changed it to a 64 bit application and it stops working.

The seg fault comes in at "if (xmlStrcmp(cur->name, (const xmlChar *) "servers"))"

cur->name is a const xmlChar * and it points to an address that says its out out bounds. But when I debug and go to that memory location, that data is correct.

int XmlGetServers()
{
xmlDocPtr doc;
xmlNodePtr cur;

doc = xmlParseFile("Pin.xml");
if (doc == NULL)
{
    std::cout << "\n Pin.xml not parsed successfully." << std::endl;
    return -1;
}
cur = xmlDocGetRootElement(doc);

if (cur == NULL)
{
    std::cout << "\n Pin.xml is empty document." << std::endl;
    xmlFreeDoc(doc);
    return -1;
}
if (xmlStrcmp(cur->name, (const xmlChar *) "servers"))
{
    std::cout << "\n ERROR: Pin.xml of the wrong type, root node != servers." << std::endl;
    xmlFreeDoc(doc);
    return -1;
}
}

Before cur is initialized the name parameter is

Name : name
    Details:0xed11f72000007fff <Address 0xed11f72000007fff out of bounds>

After cur is initialized the name parameter is

Name : name
    Details:0x64c43000000000 <Address 0x64c43000000000 out of bounds>

Referenced XML file

<?xml version="1.0"?>

<servers>

<server_info>

    <server_name>Server1</server_name>

    <server_ip>127.0.0.1</server_ip>

    <server_data_port>9000</server_data_port>

</server_info>

<server_info>

    <server_name>Server2</server_name>

    <server_ip>127.0.0.1</server_ip>

    <server_data_port>9001</server_data_port>

</server_info>

</servers>

System:

OS: Redhat Enterprise Linux 6.4 64-bit

GCC: 4.4.7-3

packages: libxml2-2.7.6-8.el6_3.4.x86_64

解决方案

The problem was that we used #pragma pack(1) in our code,which means the bools in the DOMParser are packed down to 1 byte, whereas Xerces doesn't #pragma pack and gets the default packing of 4 bytes.

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