Question

我在程序中使用map将稀疏矩阵转换为紧凑数组。

map<int, int>  m_mCustIds;
map<int, int>::iterator itr;

 for (i=0; i<m_nRatingCount; i++)
{   
Data* rating = m_aRatings + i;
itr = m_mCustIds.find(rating->CustId); 
if (itr == m_mCustIds.end())
    {
        cid = 1 + (int)m_mCustIds.size();
    }
    else
    {
        cid = itr->second;
    }
// using cid in other data structures
}

处理完固定数量（100498277）的条目后，它会给我一个分段错误。

GDB Output
Program received signal SIGSEGV, Segmentation fault.
0x0000000000401ea0 in std::less<int>::operator() (this=0x2aab0adf5ed8, __x=@0x22, __y=@0x2aab0a80f0a4)
    at /usr/lib/gcc/x86_64-redhat-linux/4.1.2/../../../../include/c++/4.1.2/bits/stl_function.h:227
227           { return __x < __y; }

bt节目

#0  0x0000000000401ea0 in std::less<int>::operator() (this=0x2aab0adf5ed8, __x=@0x22, __y=@0x2aab0a80f0a4)
    at /usr/lib/gcc/x86_64-redhat-linux/4.1.2/../../../../include/c++/4.1.2/bits/stl_function.h:227
#1  0x000000000040218f in std::_Rb_tree<int, std::pair<int const, int>, std::_Select1st<std::pair<int const, int> >, std::less<int>, std::allocator<std::pair<int const, int> > >::find (this=0x2aab0adf5ed8, __k=@0x2aab0a80f0a4) at /usr/lib/gcc/x86_64-redhat-linux/4.1.2/../../../../include/c++/4.1.2/bits/stl_tree.h:1317
#2  0x0000000000402243 in std::map<int, int, std::less<int>, std::allocator<std::pair<int const, int> > >::find (this=0x2aab0adf5ed8, __x=@0x2aab0a80f0a4)
    at /usr/lib/gcc/x86_64-redhat-linux/4.1.2/../../../../include/c++/4.1.2/bits/stl_map.h:534
#3  0x0000000000401b18 in Engine::CalcMetrics (this=0x2aaaaaad9010) at At.cpp:204
#4  0x0000000000401da3 in main () at At.cpp:141

Valgrind输出

==18544== Invalid read of size 4
==18544==    at 0x401EA0: std::less<int>::operator()(int const&, int const&) const (stl_function.h:227)
==18544==    by 0x40218E: std::_Rb_tree<int, std::pair<int const, int>, std::_Select1st<std::pair<int const, int> >, std::less<int>, std::allocator<std::pair<int const, int> > >::find(int const&) (stl_tree.h:1317)
==18544==    by 0x402242: std::map<int, int, std::less<int>, std::allocator<std::pair<int const, int> > >::find(int const&) (stl_map.h:534)
==18544==    by 0x401B17: Engine::CalcMetrics() (At.cpp:204)
==18544==    by 0x401DA2: main (At.cpp:141)
==18544==  Address 0x22 is not stack'd, malloc'd or (recently) free'd

Valgrind还报告了地图其他功能中数据丢失的可能性该程序仅使用可用系统内存的10％。

请帮忙

Answer 1

在访问itr之前，您未初始化itr->second。实际上，您根本没有为itr分配任何合法价值。

Std Map给出分段错误

1 个答案: