使用std :: map / boost :: unordered_map帮助理解segfault [英] Help understanding segfault with std::map/boost::unordered_map
问题描述
我有一些代码来处理资源（图片，字体，网格数据等）管理使用模板的静态类，允许客户端代码做如下：
ResourceManager< Texture> :: init（data / textures）;
ResourceManager< Font> :: init（data / fonts）;
//以后...
boost :: shared_ptr< const Texture> tex = ResourceManager< Texture> :: getResource（wall.png）;
boost :: shared_ptr< const Font> font = ResourceManager< Font> :: getResource（Arial.ttf）;
//以后...
ResourceManager< Texture> :: release（）;
资源类型必须有一个构造函数，并带有 const std ::
getResource 实现如下：
static boost :: shared_ptr< const ResourceType> getResource（const std :: string& fileName）
{
boost :: shared_ptr< ResourceType>资源;
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;
}
返回资源;
}
as typedef typename boost :: unordered_map< std :: string，boost :: shared_ptr< ResourceType> > table_t;
_resources 的类型为 table_t 。
问题是 boost :: unordered_map 我得到一个segfault find （源自 find_iterator ）。然而，使用 std :: map ，我得到一个segfault插入操作（源自 _Rb_tree_decrement ），或调用 find （源自 string :: compare ）。
问题只发生在请求资源的第二时间（fileName在发生故障时有效）。
这是发生在 map 和 unordered_map 我假设我必须做某事
编辑：仍然有问题，我是错了只有第二次请求资源时才发生。然而，获得资源的前2个调用是成功的，它是导致segfault的第三个调用（每个调用是针对不同的资源）。
这里是堆栈跟踪：
编程接收信号SIGSEGV，分段故障。
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_; boost :: unordered_detail :: hash_table< boost :: unordered_detail :: map< std :: string，boost :: hash< std :: string>中的
（gdb）bt
＃0 0x00000000004b4978，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在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在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在地图（这= = 0x7fffffffdfc0，fileName = ...）在/ 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在Main :: run（xResolution = 1024，yResolution = 768）在/home/tim/Projects/gameproj/app/Main.cpp:28
＃9 0x0000000000487db5在main（argc = 1，argv = 0x7fffffffe398）at /home/tim/Projects/gameproj/app/main.cpp ：10
您是否尝试过 Valgrind （假设您运行某种* nix系统）？这是一个找到内存错误的非常宝贵的工具，这看起来可能是其中之一。
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();
The "resource type" must have a constructor taking a const std::string&.
getResource is implemented as follows:
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 is defined as typedef typename boost::unordered_map< std::string, boost::shared_ptr<ResourceType> > table_t;
_resources is of type table_t.
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).
The problem only occurs the 2nd time a resource is requested (fileName is valid when the failure occurs).
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?
Thanks.
EDIT: 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).
Here is a stack trace:
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
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.
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