最近，我开始学习C ++。已经了解了一些python，我决定尝试理解指针，但是在尝试编译文件时遇到了错误。错误信息有点令人困惑，我已经坚持了一段时间。关于SO的答案确实提供了一些关于这个问题的见解，但由于我还是C ++的新手，我真的不明白如何修复它。我已经读过它可能是默认构造函数声明的问题，但我不确定要修复什么。
#include <cstddef>
#include <iostream>
using namespace std;
class Uinter
/*
* Regrouping class for intervals (_Inter class)
* offering 3 different methods:
* "reunion(int bi, int bs)" -> Unites the interval pointed by "_tete"
* with the one defined by [bi, bs]
* "printUinter()" -> Prints the interval pointed by "_tete"
* "contient(int nb)" -> Returns True if "nb" is present inside
* the intervals, else False.
*/
{
class _Inter
/*
* Class representing a single interval.
* _bi stands for the lower limit of the interval.
* _bs stands for the upper limit of the interval.
*/
{
int _bi, _bs;
_Inter* _next;
public:
_Inter(int, int, _Inter*);
// Defining getters and setters for the interval.
void set_bi(int value)
{_bi = value;}
void set_bs(int value)
{_bs = value;}
void set_next(_Inter* value)
{_next = value;}
int get_bi()
{return _bi;}
int get_bs()
{return _bs;}
_Inter* get_next()
{return _next;}
};
_Inter* _tete;
public:
Uinter(): _tete(nullptr){}
void reunion(int bi, int bs)
{
if(_tete == nullptr)
{
_Inter new_interval = _Inter(bi, bs, nullptr);
_tete = &new_interval;
}
else
{
if(bi < _tete->get_bi())
{
if (bs < _tete->get_bi())
{
_Inter new_interval = _Inter(bi, bs, _tete);
_tete = &new_interval;
}
else if (bs > _tete->get_bs())
{
_Inter new_interval = _Inter(bi, bs, _tete->get_next());
_tete = &new_interval;
}
else if (bs > _tete->get_bi())
{
_Inter new_interval = _Inter(bi, _tete->get_bs(), _tete->get_next());
_tete = &new_interval;
}
}
else if (bi > _tete->get_bi())
{
if (bi > _tete->get_bs())
{
_Inter temp = *_tete->get_next(); // delete later
while(&temp != nullptr && bi > temp.get_bs())
{
temp = *temp.get_next();
}
if (&temp == nullptr)
{
_Inter new_interval = _Inter(bi, bs, nullptr);
//temp.set_next(new_interval);
}
else if (bi < temp.get_bi()) // bi < temp.get_bs()
{
if (bs < temp.get_bi())
{
_Inter new_interval = _Inter(bi, bs, _tete);
_tete = &new_interval;
}
else if (bs > temp.get_bs())
{
_Inter new_interval = _Inter(bi, bs, _tete->get_next());
_tete = &new_interval;
}
else if (bs > temp.get_bi())
{
_Inter new_interval = _Inter(bi, _tete->get_bs(), _tete->get_next());
_tete = &new_interval;
}
}
else if (bi > temp.get_bi()) // bi < temp.get_bs()
{
if (bs > temp.get_bs())
{
_Inter new_interval = _Inter(temp.get_bi(), bs, nullptr);
temp = new_interval;
}
}
}
}
}
}
void printUinter();
bool contient(int nb);
void order();
};
int main()
{
Uinter interval;
interval.reunion(12, 23);
return 0;
}
这是错误信息 -
"/usr/bin/make" -f nbproject/Makefile-Debug.mk QMAKE= SUBPROJECTS= .build-conf
make[1]: Entering directory '/cygdrive/c/Users/Iocust/Documents/NetBeansProjects/CppApplication_2'
"/usr/bin/make" -f nbproject/Makefile-Debug.mk dist/Debug/Cygwin_4.x-Windows/cppapplication_2.exe
make[2]: Entering directory '/cygdrive/c/Users/Iocust/Documents/NetBeansProjects/CppApplication_2'
mkdir -p dist/Debug/Cygwin_4.x-Windows
g++ -std=c++11 -o dist/Debug/Cygwin_4.x-Windows/cppapplication_2 build/Debug/Cygwin_4.x-Windows/main.o
build/Debug/Cygwin_4.x-Windows/main.o: In function `Uinter::reunion(int, int)':
/cygdrive/c/Users/Iocust/Documents/NetBeansProjects/CppApplication_2/main.cpp:56: undefined reference to `Uinter::_Inter::_Inter(int, int, Uinter::_Inter*)'
/cygdrive/c/Users/Iocust/Documents/NetBeansProjects/CppApplication_2/main.cpp:56:(.text$_ZN6Uinter7reunionEii[_ZN6Uinter7reunionEii]+0x3f): relocation truncated to fit: R_X86_64_PC32 against undefined symbol `Uinter::_Inter::_Inter(int, int, Uinter::_Inter*)'
/cygdrive/c/Users/Iocust/Documents/NetBeansProjects/CppApplication_2/main.cpp:65: undefined reference to `Uinter::_Inter::_Inter(int, int, Uinter::_Inter*)'
/cygdrive/c/Users/Iocust/Documents/NetBeansProjects/CppApplication_2/main.cpp:65:(.text$_ZN6Uinter7reunionEii[_ZN6Uinter7reunionEii]+0xa4): relocation truncated to fit: R_X86_64_PC32 against undefined symbol `Uinter::_Inter::_Inter(int, int, Uinter::_Inter*)'
/cygdrive/c/Users/Iocust/Documents/NetBeansProjects/CppApplication_2/main.cpp:71: undefined reference to `Uinter::_Inter::_Inter(int, int, Uinter::_Inter*)'
/cygdrive/c/Users/Iocust/Documents/NetBeansProjects/CppApplication_2/main.cpp:71:(.text$_ZN6Uinter7reunionEii[_ZN6Uinter7reunionEii]+0xf7): relocation truncated to fit: R_X86_64_PC32 against undefined symbol `Uinter::_Inter::_Inter(int, int, Uinter::_Inter*)'
/cygdrive/c/Users/Iocust/Documents/NetBeansProjects/CppApplication_2/main.cpp:77: undefined reference to `Uinter::_Inter::_Inter(int, int, Uinter::_Inter*)'
/cygdrive/c/Users/Iocust/Documents/NetBeansProjects/CppApplication_2/main.cpp:77:(.text$_ZN6Uinter7reunionEii[_ZN6Uinter7reunionEii]+0x154): relocation truncated to fit: R_X86_64_PC32 against undefined symbol `Uinter::_Inter::_Inter(int, int, Uinter::_Inter*)'
/cygdrive/c/Users/Iocust/Documents/NetBeansProjects/CppApplication_2/main.cpp:99: undefined reference to `Uinter::_Inter::_Inter(int, int, Uinter::_Inter*)'
/cygdrive/c/Users/Iocust/Documents/NetBeansProjects/CppApplication_2/main.cpp:99:(.text$_ZN6Uinter7reunionEii[_ZN6Uinter7reunionEii]+0x23d): relocation truncated to fit: R_X86_64_PC32 against undefined symbol `Uinter::_Inter::_Inter(int, int, Uinter::_Inter*)'
build/Debug/Cygwin_4.x-Windows/main.o:/cygdrive/c/Users/Iocust/Documents/NetBeansProjects/CppApplication_2/main.cpp:105: more undefined references to `Uinter::_Inter::_Inter(int, int, Uinter::_Inter*)' follow
build/Debug/Cygwin_4.x-Windows/main.o: In function `Uinter::reunion(int, int)':
/cygdrive/c/Users/Iocust/Documents/NetBeansProjects/CppApplication_2/main.cpp:105:(.text$_ZN6Uinter7reunionEii[_ZN6Uinter7reunionEii]+0x28d): relocation truncated to fit: R_X86_64_PC32 against undefined symbol `Uinter::_Inter::_Inter(int, int, Uinter::_Inter*)'
/cygdrive/c/Users/Iocust/Documents/NetBeansProjects/CppApplication_2/main.cpp:111:(.text$_ZN6Uinter7reunionEii[_ZN6Uinter7reunionEii]+0x2e8): relocation truncated to fit: R_X86_64_PC32 against undefined symbol `Uinter::_Inter::_Inter(int, int, Uinter::_Inter*)'
/cygdrive/c/Users/Iocust/Documents/NetBeansProjects/CppApplication_2/main.cpp:119:(.text$_ZN6Uinter7reunionEii[_ZN6Uinter7reunionEii]+0x349): relocation truncated to fit: R_X86_64_PC32 against undefined symbol `Uinter::_Inter::_Inter(int, int, Uinter::_Inter*)'
collect2: error: ld returned 1 exit status
nbproject/Makefile-Debug.mk:62: recipe for target 'dist/Debug/Cygwin_4.x-Windows/cppapplication_2.exe' failed
make[2]: *** [dist/Debug/Cygwin_4.x-Windows/cppapplication_2.exe] Error 1
make[2]: Leaving directory '/cygdrive/c/Users/Iocust/Documents/NetBeansProjects/CppApplication_2'
nbproject/Makefile-Debug.mk:59: recipe for target '.build-conf' failed
make[1]: *** [.build-conf] Error 2
make[1]: Leaving directory '/cygdrive/c/Users/Iocust/Documents/NetBeansProjects/CppApplication_2'
nbproject/Makefile-impl.mk:39: recipe for target '.build-impl' failed
make: *** [.build-impl] Error 2
我很抱歉提供这么不清楚的代码。如果它有任何相关性，我使用的是NetBeans 8.0.2。
答案 0 :(得分：2)
您有链接器错误。问题出在这里：
public:
_Inter(int, int, _Inter*);
您没有定义构造函数，只是声明它，因此链接器会抱怨（它找到声明但不是定义）。如果没有它，您需要定义，不能构造对象_Inter。如果您没有为构造函数提供任何声明，那么编译器会为您生成一个默认声明，但在这种情况下，您提供了一个声明，因此不再生成默认构造函数。
您需要为Uinter::_Inter构造函数提供内联
public:
_Inter(int, int, _Inter*){/* definition here */}
或课外
Uinter::_Inter(int, int, _Inter*){/* definition here */}
可能您想要命名构造函数参数
_Inter(int param1, int param2, _Inter* param3)
因为你需要它们。