我有一个烦人的 C++ 外流错误

Question

此代码从位于 C:\a\b.txt 的 txt 文件中读取正确的 x,y 坐标集。我知道 ifstream 正在工作，因为我使用 cout 来验证。它不会为我创建新文件。有人建议使用 close()，它会创建一个文件一次。然后我又试了很多次，它不会创建文件。我正在输入：C:\a\c.txt

我认为我的代码没有任何问题。谁能发现问题或提出解决方案？

#include "lib.h"
#include <iostream>
#include <string>

using namespace std;
//....Point class and istream>> operator code

int main()
{
//....ifstream code

std::string filename;
cout << "Enter output filename: ";
std::getline(cin, filename);

ofstream ost(filename.c_str(), std::ofstream::out);
if (!ost.is_open()) cerr << "can't open output file: " << filename << endl;

    for(int i=0; i<points.size(); ++i)
        ost<<'('<<points[i].x<<','<<points[i].y<<')'<<endl;
        cout <<"got here 6"<<endl;

    ost.close();

    keep_window_open();

    return 0;

}

代码运行后，MS 编译器在输出框中给出以下消息：

project chap 10 ex 1.exe': Loaded 'C:\Windows\SysWOW64\ntdll.dll', Cannot find or open the PDB file
'project chap 10 ex 1.exe': Loaded 'C:\Program Files\AVAST Software\Avast\snxhk.dll', Cannot find or open the PDB file
'project chap 10 ex 1.exe': Loaded 'C:\Windows\SysWOW64\kernel32.dll', Cannot find or open the PDB file
'project chap 10 ex 1.exe': Loaded 'C:\Windows\SysWOW64\KernelBase.dll', Cannot find or open the PDB file
'project chap 10 ex 1.exe': Loaded 'C:\Windows\SysWOW64\msvcp100d.dll', Symbols loaded.
'project chap 10 ex 1.exe': Loaded 'C:\Windows\SysWOW64\msvcr100d.dll', Symbols loaded.
'project chap 10 ex 1.exe': Loaded 'C:\Windows\SysWOW64\user32.dll', Cannot find or open the PDB file
'project chap 10 ex 1.exe': Loaded 'C:\Windows\SysWOW64\gdi32.dll', Cannot find or open the PDB file
'project chap 10 ex 1.exe': Loaded 'C:\Windows\SysWOW64\lpk.dll', Cannot find or open the PDB file
'project chap 10 ex 1.exe': Loaded 'C:\Windows\SysWOW64\usp10.dll', Cannot find or open the PDB file
'project chap 10 ex 1.exe': Loaded 'C:\Windows\SysWOW64\msvcrt.dll', Cannot find or open the PDB file
'project chap 10 ex 1.exe': Loaded 'C:\Windows\SysWOW64\advapi32.dll', Cannot find or open the PDB file
'project chap 10 ex 1.exe': Loaded 'C:\Windows\SysWOW64\sechost.dll', Cannot find or open the PDB file
'project chap 10 ex 1.exe': Loaded 'C:\Windows\SysWOW64\rpcrt4.dll', Cannot find or open the PDB file
'project chap 10 ex 1.exe': Loaded 'C:\Windows\SysWOW64\sspicli.dll', Cannot find or open the PDB file
'project chap 10 ex 1.exe': Loaded 'C:\Windows\SysWOW64\cryptbase.dll', Cannot find or open the PDB file
'project chap 10 ex 1.exe': Loaded 'C:\Windows\SysWOW64\imm32.dll', Cannot find or open the PDB file
'project chap 10 ex 1.exe': Loaded 'C:\Windows\SysWOW64\msctf.dll', Cannot find or open the PDB file
'project chap 10 ex 1.exe': Loaded 'C:\Windows\SysWOW64\dwmapi.dll', Cannot find or open the PDB file
The thread 'Win32 Thread' (0xacc) has exited with code 0 (0x0).
The program '[6132] project chap 10 ex 1.exe: Native' has exited with code 0 (0x0).

Answer 1

#include "lib.h"
#include <iostream>
#include <string>

using namespace std;
//....Point class and istream>> operator code

int main()
{
    //....ifstream code
    ofstream ost(filename, std::ofstream::out); // filename is never initialized?
    if (ost.is_open()) 
    {
        for(int i=0; i<points.size(); ++i)
        {
            ost<<'('<<points[i].x<<','<<points[i].y<<')'<<endl;
        }
        cout <<"got here 6"<<endl;
        ost.close();
    }
    else
    {
        cerr << "Unable to open file:  " << filename << endl;
    }

    keep_window_open();
    return 0;
}

使用您显示的代码，唯一的问题（除了您可怕的格式）是您从未初始化filename，并且如果它无法打开，您仍然尝试写入ofstream。