[英]Segmentation fault (core dumped) in c++ Can't find error
我似乎無法找到錯誤的來源。 該代碼定義了一個名為boolfunc的結構。 我定義了一個函數來添加兩個boolfunc(s)。 我得到錯誤:分段錯誤(核心轉儲)。 我知道這意味着什么,但錯誤的來源在哪里。
#include<iostream>
#include<vector>
using namespace std;
class boolfunc {
public:
int num_var;
int num_terms;
vector<vector<int> > func;
boolfunc addfunc(boolfunc f1, boolfunc f2);
};
boolfunc addfunc(boolfunc f1, boolfunc f2)
{
boolfunc f3;
f3.func.resize(0);
f3.num_terms = f1.num_terms + f2.num_terms;
int var_dif = f1.num_var - f2.num_var;
if(var_dif >= 0)
{
f3.num_var=f1.num_var;
f3.func.resize(f1.num_var);
f2.num_var=f1.num_var;
f2.func.resize(f1.num_var);
for(int i=0; i<f2.num_terms; ++i)
{
for(int j=0; j<var_dif; ++j)
{
f2.func[i].push_back(-1);
}
}
}
else
{
f3.num_var=f2.num_var;
f3.func.resize(f2.num_var);
f1.num_var=f2.num_var;
f1.func.resize(f2.num_var);
for(int i=0; i<f1.num_terms; ++i)
{
for(int j=0; j<(-1)*(var_dif); ++j)
{
f1.func[i].push_back(-1);
}
}
}
for(int i=0; i<f1.num_terms; ++i)
{
f3.func[i]=f1.func[i];
}
for(int j=0; j<f2.num_terms;++j)
{
f3.func[j+f1.num_terms]=f2.func[j];
}
return f3;
}
int main()
{
boolfunc ef1, ef2, ef3;
ef1.func.resize(0);
ef2.func.resize(0);
ef3.func.resize(0);
cout<< "Input the number of variables of function 1" <<endl;
cin>> ef1.num_var;
cout<< "Input the number of variables of function 2" <<endl;
cin>> ef2.num_var;
cout<< "Input the number of terms of function 1" <<endl;
cin>> ef1.num_terms;
cout<< "Input the number of terms of function 2" <<endl;
cin>> ef2.num_terms;
ef1.func.resize(ef1.num_terms);
for(int i=0; i<ef1.num_terms; ++i)
{
ef1.func[i].resize(ef1.num_var);
for(int j=0; j<ef1.num_var; ++j)
{
cout<<"For function 1, Input the term "<<i+1<<"'s variable "<<j+1<<"'s value:";
cin>>ef1.func[i][j];
}
}
ef2.func.resize(ef2.num_terms);
for(int i=0; i<ef2.num_terms; ++i)
{
ef2.func[i].resize(ef2.num_var);
for(int j=0; j<ef2.num_var; ++j)
{
cout<<"For function 2, Input the term "<<i+1<<"'s variable "<<j+1<<"'s value:";
cin>>ef2.func[i][j];
}
}
ef3 = addfunc(ef1, ef2);
for(int i=0; i<ef3.num_terms; ++i)
{
for(int j=0; j<ef3.num_var; ++j)
{
cout<<ef3.func[i][j]<<' ';
if(j==ef3.num_var -1) cout<<endl;
}
}
return 0;
}
如何處理:
g++ -Wall -Wextra -O0 -ggdb main.cpp
gdb --args ./a.out
使用示例向量(0,0,1,0),您的程序在第49行失敗:
f3.func[i]=f1.func[i];
有錯誤:
Input the number of variables of function 1
0
Input the number of variables of function 2
0
Input the number of terms of function 1
1
Input the number of terms of function 2
0
Program received signal SIGSEGV, Segmentation fault.
0x0000000000402930 in std::vector<int, std::allocator<int> >::capacity (this=0x0) at /usr/include/c++/4.6/bits/stl_vector.h:652
652 - this->_M_impl._M_start); }
(gdb) bt
#0 0x0000000000402930 in std::vector<int, std::allocator<int> >::capacity (this=0x0) at /usr/include/c++/4.6/bits/stl_vector.h:652
#1 0x0000000000401bf3 in std::vector<int, std::allocator<int> >::operator= (this=0x0, __x=...) at /usr/include/c++/4.6/bits/vector.tcc:164
#2 0x0000000000400fc3 in addfunc (f1=..., f2=...) at main.cpp:49
#3 0x0000000000401558 in main () at main.cpp:92
如果查看程序結束的邊界並啟動標准庫,我們會立即看到錯誤:
std::vector<int, std::allocator<int> >::operator= (this=0x0, __x=...) at /usr/include/c++/4.6/bits/vector.tcc:164
如您所見, NULL
作為this
參數傳遞給std::vector<..>::operator=
,這意味着您的f3.func
向量的大小錯誤。
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