[英]Valgrind memory leak in xmlStrndup
我試圖通過遍歷元素來解析xml文件。
這是我將要調用的基本方法。 但是,每當調用此方法時,我都會觀察到泄漏。
碼:
std::string getUrl(std::vector<std::string> keyPath, std::string element, std::string fName)
{
xmlDocPtr m_doc;
xmlNodePtr m_cur;
std::string m_fileName;
bool isEmpty;
int i=0;
std::string value = "";
isEmpty = false;
m_fileName = fName;
struct stat stat_buf;
int rc = stat(m_fileName.c_str(), &stat_buf);
if(rc==0)
{
m_doc = xmlParseFile(m_fileName.c_str());
}
else
{
isEmpty = true;
}
if(isEmpty)
{
value = "Empty file found";
xmlFreeDoc(m_doc);
xmlCleanupCharEncodingHandlers();
xmlCleanupParser();
return value;
}
if(m_doc != NULL)
{
m_cur = xmlDocGetRootElement(m_doc);
}
if(m_cur != NULL)
{
if(!xmlStrcmp(m_cur->name, (const xmlChar *)(keyPath.at(i).c_str())))
{
m_cur = m_cur->xmlChildrenNode;
++i;
}
else
{
value = "root element not found";
return value;
}
while(m_cur != NULL)
{
if (!xmlStrcmp ( m_cur -> name, ( const xmlChar * ) keyPath.at(i).c_str()))
{
m_cur = m_cur->xmlChildrenNode;
i++;
}
m_cur = m_cur -> next;
if (!xmlStrcmp ( m_cur -> name, ( const xmlChar * ) keyPath.back().c_str()))
{
m_cur = m_cur->xmlChildrenNode;
break;
}
}
while (m_cur != NULL)
{
if (!xmlStrcmp ( m_cur -> name, ( const xmlChar * ) element.c_str()))
{
if(xmlNodeGetContent(m_cur->xmlChildrenNode) != NULL)
value = (char*)(xmlNodeGetContent(m_cur->xmlChildrenNode));
else
value = "";
}
m_cur = m_cur -> next;
}
}
//call the necessary cleanup APIs of libxml2 to free the dynamically allocated memory
xmlFreeDoc(m_doc);
xmlCleanupCharEncodingHandlers();
xmlCleanupParser();
if(!value.empty())
{
return value;
}
else
{
value = "value not found";
return value;
}
}
Valgrind泄漏如下:
==1598==
==1598== HEAP SUMMARY:
==1598== in use at exit: 139,402 bytes in 1,053 blocks
==1598== total heap usage: 1,222 allocs, 169 frees, 284,997 bytes allocated
==1598==
==1598== 28 bytes in 1 blocks are definitely lost in loss record 29 of 80
==1598== at 0x4C2A6FE: malloc (vg_replace_malloc.c:296)
==1598== by 0x526D928: xmlStrndup (in /usr/lib64/libxml2.so.2.9.1)
==1598== by 0x40198D: getUrl(std::vector<std::string, std::allocator<std::string> >, std::string, std::string) (in /cluster/home/XmlParser)
==1598== by 0x401BAE: parseXmlFile(std::vector<std::string, std::allocator<std::string> >, std::string, std::string) (in /cluster/home/XmlParser)
==1598== by 0x402A56: main (in /cluster/home/XmlParser)
==1598==
==1598== 28 bytes in 1 blocks are definitely lost in loss record 30 of 80
==1598== at 0x4C2A6FE: malloc (vg_replace_malloc.c:296)
==1598== by 0x526D928: xmlStrndup (in /usr/lib64/libxml2.so.2.9.1)
==1598== by 0x4019A4: getUrl(std::vector<std::string, std::allocator<std::string> >, std::string, std::string) (in /cluster/home/XmlParser)
==1598== by 0x401BAE: parseXmlFile(std::vector<std::string, std::allocator<std::string> >, std::string, std::string) (in /cluster/home/XmlParser)
==1598== by 0x402A56: main (in /cluster/home/XmlParser)
==1598==
==1598== 30 bytes in 1 blocks are definitely lost in loss record 31 of 80
==1598== at 0x4C2A6FE: malloc (vg_replace_malloc.c:296)
==1598== by 0x526D928: xmlStrndup (in /usr/lib64/libxml2.so.2.9.1)
==1598== by 0x40198D: getUrl(std::vector<std::string, std::allocator<std::string> >, std::string, std::string) (in /cluster/home/XmlParser)
==1598== by 0x401BAE: parseXmlFile(std::vector<std::string, std::allocator<std::string> >, std::string, std::string) (in /cluster/home/XmlParser)
==1598== by 0x402CD2: main (in /cluster/home/XmlParser)
==1598==
==1598== 30 bytes in 1 blocks are definitely lost in loss record 32 of 80
==1598== at 0x4C2A6FE: malloc (vg_replace_malloc.c:296)
==1598== by 0x526D928: xmlStrndup (in /usr/lib64/libxml2.so.2.9.1)
==1598== by 0x4019A4: getUrl(std::vector<std::string, std::allocator<std::string> >, std::string, std::string) (in /cluster/home/XmlParser)
==1598== by 0x401BAE: parseXmlFile(std::vector<std::string, std::allocator<std::string> >, std::string, std::string) (in /cluster/home/XmlParser)
==1598== by 0x402CD2: main (in /cluster/home/XmlParser)
==1598==
==1598== 30 bytes in 1 blocks are definitely lost in loss record 33 of 80
==1598== at 0x4C2A6FE: malloc (vg_replace_malloc.c:296)
==1598== by 0x526D928: xmlStrndup (in /usr/lib64/libxml2.so.2.9.1)
==1598== by 0x40198D: getUrl(std::vector<std::string, std::allocator<std::string> >, std::string, std::string) (in /cluster/home/XmlParser)
==1598== by 0x401FF4: parseXmlFile(std::vector<std::string, std::allocator<std::string> >, std::string, std::string) (in /cluster/home/XmlParser)
==1598== by 0x402F30: main (in /cluster/home/XmlParser)
==1598==
==1598== 30 bytes in 1 blocks are definitely lost in loss record 34 of 80
==1598== at 0x4C2A6FE: malloc (vg_replace_malloc.c:296)
==1598== by 0x526D928: xmlStrndup (in /usr/lib64/libxml2.so.2.9.1)
==1598== by 0x4019A4: getUrl(std::vector<std::string, std::allocator<std::string> >, std::string, std::string) (in /cluster/home/XmlParser)
==1598== by 0x401FF4: parseXmlFile(std::vector<std::string, std::allocator<std::string> >, std::string, std::string) (in /cluster/home/XmlParser)
==1598== by 0x402F30: main (in /cluster/home/XmlParser)
==1598==
==1598== 21,852 (176 direct, 21,676 indirect) bytes in 1 blocks are definitely lost in loss record 77 of 80
==1598== at 0x4C2A6FE: malloc (vg_replace_malloc.c:296)
==1598== by 0x5215324: xmlNewDoc (in /usr/lib64/libxml2.so.2.9.1)
==1598== by 0x52C01B8: xmlSAX2StartDocument (in /usr/lib64/libxml2.so.2.9.1)
==1598== by 0x520E25D: xmlParseDocument (in /usr/lib64/libxml2.so.2.9.1)
==1598== by 0x520E561: xmlSAXParseFileWithData (in /usr/lib64/libxml2.so.2.9.1)
==1598== by 0x40181A: getUrl(std::vector<std::string, std::allocator<std::string> >, std::string, std::string) (in /cluster/home/XmlParser)
==1598== by 0x401BAE: parseXmlFile(std::vector<std::string, std::allocator<std::string> >, std::string, std::string) (in /cluster/home/XmlParser)
==1598== by 0x402A56: main (in /cluster/home/XmlParser)
==1598==
==1598== 21,852 (176 direct, 21,676 indirect) bytes in 1 blocks are definitely lost in loss record 78 of 80
==1598== at 0x4C2A6FE: malloc (vg_replace_malloc.c:296)
==1598== by 0x5215324: xmlNewDoc (in /usr/lib64/libxml2.so.2.9.1)
==1598== by 0x52C01B8: xmlSAX2StartDocument (in /usr/lib64/libxml2.so.2.9.1)
==1598== by 0x520E25D: xmlParseDocument (in /usr/lib64/libxml2.so.2.9.1)
==1598== by 0x520E561: xmlSAXParseFileWithData (in /usr/lib64/libxml2.so.2.9.1)
==1598== by 0x40181A: getUrl(std::vector<std::string, std::allocator<std::string> >, std::string, std::string) (in /cluster/home/XmlParser)
==1598== by 0x401BAE: parseXmlFile(std::vector<std::string, std::allocator<std::string> >, std::string, std::string) (in /cluster/home/XmlParser)
==1598== by 0x402CD2: main (in /cluster/home/XmlParser)
==1598==
==1598== 21,852 (176 direct, 21,676 indirect) bytes in 1 blocks are definitely lost in loss record 79 of 80
==1598== at 0x4C2A6FE: malloc (vg_replace_malloc.c:296)
==1598== by 0x5215324: xmlNewDoc (in /usr/lib64/libxml2.so.2.9.1)
==1598== by 0x52C01B8: xmlSAX2StartDocument (in /usr/lib64/libxml2.so.2.9.1)
==1598== by 0x520E25D: xmlParseDocument (in /usr/lib64/libxml2.so.2.9.1)
==1598== by 0x520E561: xmlSAXParseFileWithData (in /usr/lib64/libxml2.so.2.9.1)
==1598== by 0x40181A: getUrl(std::vector<std::string, std::allocator<std::string> >, std::string, std::string) (in /cluster/home/XmlParser)
==1598== by 0x401FF4: parseXmlFile(std::vector<std::string, std::allocator<std::string> >, std::string, std::string) (in /cluster/home/XmlParser)
==1598== by 0x402F30: main (in /cluster/home/XmlParser)
==1598==
==1598== LEAK SUMMARY:
==1598== definitely lost: 704 bytes in 9 blocks
==1598== indirectly lost: 65,028 bytes in 1,023 blocks
==1598== possibly lost: 0 bytes in 0 blocks
==1598== still reachable: 73,670 bytes in 21 blocks
==1598== suppressed: 0 bytes in 0 blocks
==1598== Reachable blocks (those to which a pointer was found) are not shown.
==1598== To see them, rerun with: --leak-check=full --show-leak-kinds=all
==1598==
==1598== For counts of detected and suppressed errors, rerun with: -v
==1598== ERROR SUMMARY: 9 errors from 9 contexts (suppressed: 0 from 0)
如果您能幫助我真正造成泄漏的事情,我將不勝感激。 提前致謝
這段代碼導致了兩次內存泄漏:
if(xmlNodeGetContent(m_cur->xmlChildrenNode) != NULL)
value = (char*)(xmlNodeGetContent(m_cur->xmlChildrenNode));
else
value = "";
xmlNodeGetContent
返回必須使用xmlFree
釋放的字符串。 因此,代碼應如下所示:
xmlChar *content = xmlNodeGetContent(m_cur->xmlChildrenNode);
if (content != NULL) {
value = (char*)content;
xmlFree(content);
}
else {
value = "";
}
您有時還會泄漏xmlDoc
。 這可能是由於無法釋放文檔的“找不到根元素”返回路徑引起的。
現在,nwellnhof已為您解答了泄漏點所在的問題。
我會盡力告訴您如何修復它們。 注意未經測試的代碼。
我們在這里(st-)使用std::unique_ptr
作為scope_guard。
首先創建一個通用的獲取字符串方法,該方法可以解決無字符串問題。
std::string xmlGetString(xmlNodePtr m_cur) {
std::unique_ptr<xmlChar>
content(xmlNodeGetContent(m_cur->xmlChildrenNode), xmlFree); // 1
if (content != NULL) {
return (char*)content;
} else {
return "";
}
}
注意1:xmlFree是std::unique_ptr
的刪除器
如果xmlFree的答案不為NULL,則必須在調用xmlFree之前將其打包到另一個檢查NULL的方法中。
(這看起來效率很低,xmlNodeGetContent復制了一些內部數據,然后以std::string
返回,需要文本的另一個副本,至少可以省略字符串到調用方中左值的最終副本。 )
與xmlFreeDoc
相同的技巧,首先進行一些重寫
if (rc != 0) {
// any other xml clean up needed???
return "Empty file found";
}
然后將其聲明為
std::unique_ptr<xmlDoc> m_doc(xmlParseFile(m_fileName.c_str()), Cleanup);
// note the ptr is gone to the unique_ptr
和其他方法
void Cleanup(xmlDocPtr m_doc) {
xmlFreeDoc(m_doc);
xmlCleanupCharEncodingHandlers();
xmlCleanupParser();
}
然后,當m_doc離開范圍時,將調用Cleanup
。
現在您需要清理,以免做不必要的工作。
您應該將所有其他xml函數打包到某些c ++中,或者更改xml庫。
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