valgrind未检测到的malloc_consolidate(malloc.c)中的分段错误

Question

我的程序进入分段错误,我找不到原因.最糟糕的是,所讨论的功能并不总是导致段错误.

GDB确认错误并产生这种回溯:

Program received signal SIGSEGV, Segmentation fault.
0xb7da6d6e in malloc_consolidate (av=<value optimized out>) at malloc.c:5169
5169  malloc.c: No such file or directory.
  in malloc.c
(gdb) bt
#0  0xb7da6d6e in malloc_consolidate (av=<value optimized out>) at malloc.c:5169
#1  0xb7da9035 in _int_malloc (av=<value optimized out>, bytes=<value optimized out>) at malloc.c:4373
#2  0xb7dab4ac in __libc_malloc (bytes=525) at malloc.c:3660
#3  0xb7f8dc15 in operator new(unsigned int) () from /usr/lib/i386-linux-gnu/libstdc++.so.6
#4  0xb7f72db5 in std::basic_string<char, std::char_traits<char>, std::allocator<char> >::_Rep::_S_create(unsigned int, unsigned int, std::allocator<char> const&) ()
   from /usr/lib/i386-linux-gnu/libstdc++.so.6
#5  0xb7f740bf in std::basic_string<char, std::char_traits<char>, std::allocator<char> >::_Rep::_M_clone(std::allocator<char> const&, unsigned int) ()
   from /usr/lib/i386-linux-gnu/libstdc++.so.6
#6  0xb7f741f1 in std::basic_string<char, std::char_traits<char>, std::allocator<char> >::reserve(unsigned int) () from /usr/lib/i386-linux-gnu/libstdc++.so.6
#7  0xb7f6bfec in std::basic_stringbuf<char, std::char_traits<char>, std::allocator<char> >::overflow(int) () from /usr/lib/i386-linux-gnu/libstdc++.so.6
#8  0xb7f70e1c in std::basic_streambuf<char, std::char_traits<char> >::xsputn(char const*, int) () from /usr/lib/i386-linux-gnu/libstdc++.so.6
#9  0xb7f5b498 in std::ostreambuf_iterator<char, std::char_traits<char> > std::num_put<char, std::ostreambuf_iterator<char, std::char_traits<char> > >::_M_insert_int<unsigned long>(std::ostreambuf_iterator<char, std::char_traits<char> >, std::ios_base&, char, unsigned long) const () from /usr/lib/i386-linux-gnu/libstdc++.so.6
#10 0xb7f5b753 in std::num_put<char, std::ostreambuf_iterator<char, std::char_traits<char> > >::do_put(std::ostreambuf_iterator<char, std::char_traits<char> >, std::ios_base&, char, unsigned long) const () from /usr/lib/i386-linux-gnu/libstdc++.so.6
#11 0xb7f676ac in std::basic_ostream<char, std::char_traits<char> >& std::basic_ostream<char, std::char_traits<char> >::_M_insert<unsigned long>(unsigned long) ()
   from /usr/lib/i386-linux-gnu/libstdc++.so.6
#12 0xb7f67833 in std::basic_ostream<char, std::char_traits<char> >::operator<<(unsigned int) () from /usr/lib/i386-linux-gnu/libstdc++.so.6
#13 0x08049c42 in sim::Address::GetS (this=0xbfffec40) at address.cc:27
#14 0x0806a499 in sim::UserGenerator::ProcessEvent (this=0x80a1af0, e=...) at user-generator.cc:59
#15 0x0806694b in sim::Simulator::CommunicateEvent (this=0x809f970, e=...) at simulator.cc:144
#16 0x0806685d in sim::Simulator::ProcessNextEvent (this=0x809f970) at simulator.cc:133
#17 0x08065d76 in sim::Simulator::Run (seed=0) at simulator.cc:53
#18 0x0807ce85 in main (argc=1, argv=0xbffff454) at main.cc:75
(gdb) f 13
#13 0x08049c42 in sim::Address::GetS (this=0xbfffec40) at address.cc:27
27    oss << m_address;
(gdb) p this->m_address
$1 = 1

GetS类Address的方法将数字(uint32_t m_address)转换为字符串并返回它.代码(非常简单)如下:

std::string
Address::GetS () const
{
  std::ostringstream oss;
  oss << m_address;
  return oss.str ();
}

此外,正如在回溯中可以看到的那样,m_address是正确定义的.

现在,我尝试使用valgrind运行我的程序.该程序不会崩溃,可能是因为valgrind取代malloc ()了其他功能.

错误摘要显示没有内存泄漏:

LEAK SUMMARY:
   definitely lost: 0 bytes in 0 blocks
   indirectly lost: 0 bytes in 0 blocks
     possibly lost: 4,367 bytes in 196 blocks
   still reachable: 9,160 bytes in 198 blocks
        suppressed: 0 bytes in 0 blocks

所有这些都是possibly lost指这样的回溯:

80 bytes in 5 blocks are possibly lost in loss record 3 of 26
   at 0x4024B64: operator new(unsigned int) (in /usr/lib/valgrind/vgpreload_memcheck-x86-linux.so)
   by 0x40DBDB4: std::string::_Rep::_S_create(unsigned int, unsigned int, std::allocator<char> const&) (in /usr/lib/i386-linux-gnu/libstdc++.so.6.0.16)
   by 0x40DE077: 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.6.0.16)
   by 0x40DE1E5: 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.6.0.16)
   by 0x806AF62: sim::UserGenerator::CreateUser(unsigned int) (user-generator.cc:152)

我不认为这与bug有关.但是,可以在此链接后找到相关代码.

我在考虑一个错误libstdc++.但是,这有多大可能？我也升级了这样的库.这是我系统上当前安装的版本.

$ dpkg -l | grep libstdc
ii  libstdc++5          1:3.3.6-23  The GNU Standard C++ Library v3
ii  libstdc++6          4.6.1-1     GNU Standard C++ Library v3
ii  libstdc++6-4.1-dev  4.1.2-27    The GNU Standard C++ Library v3 (development files)
ii  libstdc++6-4.3-dev  4.3.5-4     The GNU Standard C++ Library v3 (development files)
ii  libstdc++6-4.4-dev  4.4.6-6     GNU Standard C++ Library v3 (development files)
ii  libstdc++6-4.5-dev  4.5.3-3     The GNU Standard C++ Library v3 (development files)
ii  libstdc++6-4.6-dev  4.6.1-1     GNU Standard C++ Library v3 (development files)

现在问题是,我不确定g++使用哪个版本,以及是否有一些方法来强制使用特定版本.

我在思考的是修改GetS.但这是我所知道的唯一方法.你有什么选择吗？

最终,我甚至考虑std::string更简单地替换char*.也许有点激烈,但我不会把它放在一边.

有什么想法吗？

谢谢大家.

最好,吉尔

Answer 1

好.这不是问题:

我在想libstdc ++中的一个bug

问题是你覆盖了一些内存缓冲区并破坏了内存管理器使用的一种结构.困难的部分将是找到它.valgrind不会为您提供有关写入已分配内存的结尾的信息.

不要这样做:

最后,我甚至考虑用更简单的char*替换std :: string.也许有点激烈,但我不会把它放在一边.

您已经有足够的内存管理问题.这只会增加更多问题.std :: string或内存管理例程绝对没有错.它们经过严格测试和使用.如果有什么不对劲的话,全世界的人都会开始尖叫(这将是个大新闻).

在http://mercurial.intuxication.org/hg/lte_sim/file/c2ef6e0b6d41/src/它上面阅读你的代码似乎仍然陷入了C风格的代码编写(C with Classes).所以你拥有C++的强大功能来自动化(代码的爆炸),但仍然存在与C相关的所有问题.

您需要在所有权方面重新查看代码.你通过指针方式传递的东西太多了.因此,很难遵循指针的所有权(因此谁负责删除它).

我认为最好的办法是找出错误就是为每个班级编写单元测试.然后通过val-grind运行单元测试.我知道这是一种痛苦(但你应该已经做到了,现在你可以一次性完成疼痛).