帮助理解segfault与std :: map / boost :: unordered_map [英] Help understanding segfault with std::map/boost::unordered_map

问题描述

我有一些代码可以使用模板的静态类来处理资源（图像，字体，网格数据等）管理，允许客户端代码执行以下操作：

I have some code to handle resource (images, fonts, mesh data, etc.) management using a template'd static class, allowing client code to do something like:

ResourceManager<Texture>::init("data/textures");
ResourceManager<Font>::init("data/fonts");
// later ...
boost::shared_ptr<const Texture> tex = ResourceManager<Texture>::getResource("wall.png");
boost::shared_ptr<const Font> font = ResourceManager<Font>::getResource("Arial.ttf");
// later ...
ResourceManager<Texture>::release();

资源类型必须具有构造函数，采用 const std ::字符串& 。

The "resource type" must have a constructor taking a const std::string&.

getResource 的实现如下：

static boost::shared_ptr<const ResourceType> getResource(const std::string& fileName)
{
    boost::shared_ptr<ResourceType> resource;

    typename table_t::const_iterator itr = _resources.find(fileName);
    if (itr == _resources.end()) {
        resource.reset(new ResourceType(_dataDirectory + fileName));
        _resources[fileName] = resource;
    } else {
        resource = itr->second;
    }

    return resource;
}

table_t as typedef typename boost :: unordered_map< std :: string，boost :: shared_ptr< ResourceType> > table_t;

_resources 的类型为 table_t 。

_resources is of type table_t.

问题出在 boost :: unordered_map 我得到一个segfault的呼叫 find （源自 find_iterator ）。但是，使用 std :: map ，我可以在插入操作中获得一个segfault（源自 _Rb_tree_decrement ），或者调用 find （源自 string :: compare ）。

The problem is with boost::unordered_map I get a segfault on the call to find (originating from find_iterator). However, with std::map instead, I either get a segfault on the insert operation (originating from _Rb_tree_decrement), or on the call to find (originating from string::compare).

问题只发生在请求资源的 2nd 时间（fileName在发生故障时有效）

The problem only occurs the 2nd time a resource is requested (fileName is valid when the failure occurs).

正如我们假设我一定要做的事情一样，这两个都是 map 和 unordered_map 奇怪的地方导致这个，任何想法？

As this is happening with both map and unordered_map I'm assuming I must be doing something bizarre somewhere to cause this, any ideas?

谢谢。

编辑：仍然有问题，我是错误的只是发生在第二次资源被请求。然而，获得资源的前2个调用是成功的，这是导致segfault的第三个调用（每个调用是针对不同的资源）。

Still having the problem, I was wrong about it only happening the 2nd time a resource is requested. However, the first 2 calls to get a resource are successful, it's the 3rd call that is causing the segfault (each call is for a different resource).

这是一个堆栈跟踪：

Program received signal SIGSEGV, Segmentation fault.
0x00000000004b4978 in boost::unordered_detail::hash_table<boost::unordered_detail::map<std::string, boost::hash<std::string>, std::equal_to<std::string>, std::allocator<std::pair<std::string const, boost::shared_ptr<Texture> > > > >::find_iterator (this=0x7aed80, bucket=0x38, k=...)
    at /usr/local/include/boost/unordered/detail/table.hpp:55
55          node_ptr it = bucket->next_;
(gdb) bt
#0  0x00000000004b4978 in boost::unordered_detail::hash_table<boost::unordered_detail::map<std::string, boost::hash<std::string>, std::equal_to<std::string>, std::allocator<std::pair<std::string const, boost::shared_ptr<Texture> > > > >::find_iterator (this=0x7aed80, bucket=0x38, k=...)
    at /usr/local/include/boost/unordered/detail/table.hpp:55
#1  0x00000000004b294c in boost::unordered_detail::hash_table<boost::unordered_detail::map<std::string, boost::hash<std::string>, std::equal_to<std::string>, std::allocator<std::pair<std::string const, boost::shared_ptr<Texture> > > > >::find (this=0x7aed80, k=...)
    at /usr/local/include/boost/unordered/detail/table.hpp:583
#2  0x00000000004b07c1 in boost::unordered_map<std::string, boost::shared_ptr<Texture>, boost::hash<std::string>, std::equal_to<std::string>, std::allocator<std::pair<std::string const, boost::shared_ptr<Texture> > > >::find (this=0x7aed80, k=...)
    at /usr/local/include/boost/unordered/unordered_map.hpp:423
#3  0x00000000004ae7c6 in ResourceManager<Texture>::getResource (fileName=...) at /home/tim/Projects/gameproj/app/ResourceManager.hpp:52
#4  0x00000000004ce7fc in Map::loadCellTextures (this=0x7fffffffdfc0, in=...) at /home/tim/Projects/gameproj/app/Map.cpp:57
#5  0x00000000004ce632 in Map (this=0x7fffffffdfc0, fileName=...) at /home/tim/Projects/gameproj/app/Map.cpp:30
#6  0x0000000000495702 in Game::init (xResolution=1024, yResolution=768) at /home/tim/Projects/gameproj/app/Game.cpp:116
#7  0x0000000000494fa0 in Game::run (xResolution=1024, yResolution=768) at /home/tim/Projects/gameproj/app/Game.cpp:38
#8  0x0000000000487f1d in Main::run (xResolution=1024, yResolution=768) at /home/tim/Projects/gameproj/app/Main.cpp:28
#9  0x0000000000487db5 in main (argc=1, argv=0x7fffffffe398) at /home/tim/Projects/gameproj/app/main.cpp:10

推荐答案

我无法发现任何明显错误，您是否尝试过 Valgrind （假设你运行某种* nix系统）？这是发现内存错误的宝贵工具，而这似乎可能是其中之一。

I can't spot any obvious errors, have you tried Valgrind (assuming you run some kind of *nix system)? It's an invaluable tool for finding memory errors, and this looks like it might be one of those.

这篇关于帮助理解segfault与std :: map / boost :: unordered_map的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！