解释Valgrind内存泄漏总结日志

我正在使用Valgrind（一种内存泄漏工具）来查找潜在的内存泄漏。它是这样运行的：

$valgrind--泄漏检查=已满/myApp

报告如下：

==9458== 15,007 bytes in 126 blocks are possibly lost in loss record 622 of 622
==9458==    at 0x4029FDE: operator new(unsigned int) (vg_replace_malloc.c:313)
==9458==    by 0x415F213: std::string::_Rep::_S_create(unsigned int, unsigned int, std::allocator<char> const&) (in /usr/lib/i386-linux-gnu/libstdc++.so.6.0.19)
==9458==    by 0x4161125: char* std::string::_S_construct<char const*>(char const*, char const*, std::allocator<char> const&, std::forward_iterator_tag) (in /usr/lib/i386-linux-gnu/libstdc++.so.6.0.19)
==9458==    by 0x41617AF: std::basic_string<char, std::char_traits<char>, std::allocator<char> >::basic_string(char const*, std::allocator<char> const&) (in /usr/lib/i386-linux-gnu/libstdc++.so.6.0.19)
==9458==    by 0x808B061: Parser::parseLinear(rapidxml::xml_node<char>*, Linear*) (Parser.cpp:663)
==9458== 
==9458== LEAK SUMMARY:
==9458==    definitely lost: 0 bytes in 0 blocks
==9458==    indirectly lost: 0 bytes in 0 blocks
==9458==      possibly lost: 20,747 bytes in 257 blocks
==9458==    still reachable: 57,052 bytes in 3,203 blocks
==9458==         suppressed: 0 bytes in 0 blocks
==9458== Reachable blocks (those to which a pointer was found) are not shown.
==9458== To see them, rerun with: --leak-check=full --show-leak-kinds=all
==9458== 
==9458== For counts of detected and suppressed errors, rerun with: -v
==9458== ERROR SUMMARY: 21 errors from 21 contexts (suppressed: 0 from 0)

根据总结，似乎存在"可能丢失"的内存泄漏。然而，在Parser.cpp中追踪到663行之后，我似乎无法确定问题所在。xml_node<>*是开源库RapidXML的一部分。源代码如下：

line 661: Tracker track;
line 662: xml_node<>* trackingNode = node->first_node(); // rapidxml API
line 663: track.setValue(trackingNode->first_node()->value());

其中setValue定义为：

void Tracker::setValue(const string& s) {
    this->val = s;
}