Question

在我搜索了如何验证指针是否在C ++中被删除之后，我发现没有特定的方法，一些非常难看的解决方法或智能指针（我首先要了解正常指针是如何工作的）。我的问题是当我尝试使用try / catch来显示已删除指针的值时C ++崩溃的原因？它不应该处理崩溃并只打印异常??

void main()
{
    int *a = new int[5];

    for (int i = 0; i < 5; i++)
    {
        *(a + i) = i;
    }

    for (int i = 0; i < 5; i++)
    {
        if (*(a + i) != NULL) // useless verify, cuz if it would be NULL, it 
                              //would crash imediately
        {
            cout << (a + i) << ", " << *(a + i) << endl;
        }
    }

    delete a;
    cout << a << ", ";// << *a << endl;

    for (int i = 0; i < 5; i++)
    {
        try{
            cout << (a + i) << ", " << *(a + i) << endl;
        }
        catch (int e)
        {
            cout << "Error: " << e << endl;
        }
    }

    cin.get();
}

Answer 1

try{
        cout << (a + i) << ", " << *(a + i) << endl;
    }
    catch (int e)
    {
        cout << "Error: " << e << endl;
    }

只有在抛出异常时才能捕获异常。访问释放的内存是Undefined Beahvior并且不会抛出异常，因此无需捕获。

Answer 2

首先对于数组删除，语法为Sub Import_text() Dim xWb As Workbook Dim xToBook As Workbook Dim xStrPath As String Dim xFileDialog As FileDialog Dim xFile As String Dim xFiles As New Collection Dim I As Long Set xFileDialog = Application.FileDialog(msoFileDialogFolderPicker) xFileDialog.AllowMultiSelect = True xFileDialog.Title = "Select a folder" If xFileDialog.Show = -1 Then xStrPath = xFileDialog.SelectedItems(1) End If If xStrPath = "" Then Exit Sub If Right(xStrPath, 1) <> "\" Then xStrPath = xStrPath & "\" 'xFile = Dir(xStrPath) xFile = Dir(xStrPath & "*.txt") 'this is the original version that you can amend according to file extension If xFile = "" Then MsgBox "No files found", vbInformation, "Summary" Exit Sub End If Do While xFile <> "" xFiles.Add xFile, xFile xFile = Dir() Loop Set xToBook = ThisWorkbook If xFiles.Count > 0 Then For I = 1 To xFiles.Count Set xWb = Workbooks.Open(xStrPath & xFiles.Item(I)) xWb.Worksheets(1).Copy after:=xToBook.Sheets(xToBook.Sheets.Count) On Error Resume Next ActiveSheet.Name = xWb.Name On Error GoTo 0 xWb.Close False Next End If End Sub其次，try catch块不用于处理损坏的地址，不幸的是C ++中的内存访问冲突没有异常处理。

Answer 3

在这种情况下，没有异常抛出，只是未定义的行为。例外情况是明确捕获正在抛出的异常。

另外，使用delete [] a;代替delete a;删除数组。

此外，当我们delete内存时，内存实际上并未实现已删除，但从现在开始可以自由覆盖。

cout打印的内容并未说明指针是否为deleted。

删除指针后的C ++ try / catch

3 个答案: