msftedit "Access violation reading location 0x00000008"错误.dll SetWindowSub类中的RichEdit控件

Error "Access violation reading location 0x00000008" with msftedit.dll RichEdit control inside SetWindowSubclass

本文关键字：SetWindowSub RichEdit 控件 dll 错误 violation Access reading location 0x00000008 msftedit      更新时间：2023-10-16

我在单独的子类文件中拥有编辑控件。在开始使用SetWindowSubclass函数后(我是C++的新手，以前我使用SetWindowLongPtr进行子类划分，它运行良好，但有人建议我开始使用SetWindowsSubclass)，我遇到了这个问题：

编译程序后，应用程序绘制空窗口，该窗口立即停止响应(我必须通过任务管理器关闭它)。输出窗口中的结果错误：

TaskTracklist.exe中0x635F3DEF(msftedit.dll)处引发异常：0xC0000005:读取位置0x00000008时发生访问冲突。

完整代码：

#include "stdafx.h"
#include <windows.h>
#include <commctrl.h>
#include <richedit.h>
#include <string.h>
#include "SearchEditBox.h"
/*global vars*/
LPCWSTR SearchEditBox::editBoxDefText = L"Search...";
bool SearchEditBox::firstLoad = false;
int SearchEditBox::width = 0;
int SearchEditBox::height = 0;
HWND SearchEditBox::editBox;
/*functions*/
LRESULT CALLBACK EditBoxProc(HWND hwnd, UINT uMsg, WPARAM wParam, LPARAM lParam, UINT_PTR uint_ptr, DWORD dwRefData);
void ChangeEdit(const HWND hwnd, const bool change);
/*set-get functions*/
HWND SearchEditBox::getEditBox()
{
return SearchEditBox::editBox;
}
SearchEditBox * SearchEditBox::CreateEditBox(HINSTANCE hInst, HWND hwnd, int pos_x, int pos_y, int width, int height) {
SearchEditBox * p_SearchEditBox = new SearchEditBox;
LoadLibrary(TEXT("Msftedit.dll")); //enables RichEdit field
SearchEditBox::editBox = CreateWindowEx(0, (L"RICHEDIT50W"), editBoxDefText, WS_VISIBLE | WS_CHILD, pos_x + 6, pos_y + 4, width, height, hwnd, NULL, (HINSTANCE)GetWindowLong(hwnd, GWL_HINSTANCE), p_SearchEditBox);
SearchEditBox::width = width;
SearchEditBox::height = height;
if (SearchEditBox::editBox == NULL)
{
delete p_SearchEditBox;
MessageBox(NULL, L"Problem creating the Search box.", L"Error", 0);
return 0;
}
SetWindowSubclass(SearchEditBox::editBox, SearchEditBox::EditBoxProc, 0, 0);
return p_SearchEditBox;
}
LRESULT CALLBACK SearchEditBox::EditBoxProc(HWND hwnd, UINT uMsg, WPARAM wParam, LPARAM lParam, UINT_PTR uIdSubclass, DWORD dwRefData)
{
PAINTSTRUCT ps;
HDC hdc;
switch (uMsg)
{
case WM_SETFOCUS:
{
LPWSTR getText = new TCHAR[10];
GetWindowText(hwnd, getText, 10);
if (_tcscmp(getText, editBoxDefText) == 0)
{
SearchEditBox::ChangeEdit(hwnd, 1);
}
delete getText;
break;
}
case WM_KILLFOCUS:
{
LPWSTR getText = new TCHAR[10];
if (GetWindowText(hwnd, getText, 10) == 0)
{
SearchEditBox::ChangeEdit(hwnd, 0);
}
::SetFocus(NULL);
delete getText;
break;
}
case WM_LBUTTONDBLCLK:
SearchEditBox::ChangeEdit(hwnd, 1);
break;
case WM_PAINT:
{
hdc = BeginPaint(hwnd, &ps);
RECT rc;
InvalidateRect(hwnd, &rc, 0);
if (SearchEditBox::firstLoad == false)
{
SearchEditBox::ChangeEdit(hwnd, 0);
::SetFocus(NULL);
SearchEditBox::firstLoad = true;
}
HBRUSH hBrush = CreateSolidBrush(RGB(33, 33, 33));
SelectObject(hdc, hBrush);
RoundRect(hdc, -6, -4, SearchEditBox::width + 7, SearchEditBox::height + 4, 5, 5);
EndPaint(hwnd, &ps);
break;
}
}
return DefSubclassProc(hwnd, uMsg, lParam, wParam);
}

我很清楚，问题出在带有SetWindowSubclass函数的RichEdit控件上。

尽管我在Msftedit.dll的连接中没有发现任何与此错误相关的主题，但我从这些文章(这里和这里)中了解到，我可能引用了NULL指针，但这对我来说没有意义，因为那样我会从SetWindowSubclass函数上方的这一位得到错误(我没有)：

if (SearchEditBox::editBox == NULL)
{
delete p_SearchEditBox;
MessageBox(NULL, L"Problem creating the Search box.", L"Error", 0);
return 0;
}

我还认为问题可能是外部函数(意味着在comctl32中定义的函数，而不是在类内部)访问类特定变量(指针不会为NULL，但函数可能无法访问它)，所以我尝试仅为SetWindowSubclass函数创建局部变量(也不起作用)：

HWND newHWND = SearchEditBox::editBox;
SetWindowSubclass(newHWND, SearchEditBox::EditBoxProc, 0, 0);

使用函数getEditBox()也不能解决这个问题。

我还尝试在控件声明中使用MSFTEDIT_CLASS而不是(L"RICHEDIT50W")(认为问题可能在控件本身内部)，但这也没有帮助，并且尝试不同的版本(例如RICHEDIT51W或RICHEDIT80W)会导致错误(所以我必须使用VS2015的正确RichEdit版本)。

我还尝试在CreateEditBox中声明HWND-editBox(使其成为局部变量)，但这也没有帮助。

我使用免费社区版本的VS.

编辑：从代码中清除了一些未成功的尝试。

TaskTracklist.exe中0x635F3DEF(msftedit.dll)处引发异常：0xC0000005:读取位置0x00000008时发生访问冲突。

地址0附近的访问冲突通常意味着通过NULL对象指针访问类/记录数据成员。

尽管我在Msftedit.dll的连接中没有发现任何与此错误相关的主题，但我从这些文章(…)中了解到，我可能引用了NULL指针，但这对我来说没有意义，因为那样我会从SetWindowSubclass函数(我没有)上方的这一位得到错误

此问题与访问NULLHWND句柄无关。它与访问NULL对象指针有关。而且您的代码中确实有对象指针，所以您需要弄清楚哪一个是NULL。当发生AccessViolation时，请使用调试器查看在内存地址0x635F3DEF处运行的代码，这将导致代码中的哪一行崩溃。

话虽如此，EditBoxProc()的最后一个参数需要是DWORD_PTR而不是DWORD，并且您以错误的顺序将wParam和lParam值传递给DefSubclassProc()。

此外，WM_KILLFOCUS和WM_PAINT处理程序不应调用SetFocus()，WM_PAINT处理程序不应该调用InvalidateRect()。

我建议您重写SearchEditBox类，使其数据成员不再是static。在类中使它们成为static可以防止创建多个具有单个HWNDs的SearchEditBox对象。数据成员不需要是static。您可以传递SearchEditBox*指针作为子类的dwRefData参数，这样EditBoxProc()就可以访问SearchEditBox对象及其非静态成员。

试试类似的东西：

SearchEditBox.h

#ifndef SearchEditBoxH
#define SearchEditBoxH
class SearchEditBox
{
private:
bool firstPaint;
int width;
int height;
HWND editBox;
SearchEditBox();
void ChangeEdit(const bool change);
static LRESULT CALLBACK EditBoxProc(HWND hwnd, UINT uMsg, WPARAM wParam, LPARAM lParam, UINT_PTR uint_ptr, DWORD_PTR dwRefData);
public:
~SearchEditBox();
HWND getEditBox()
static SearchEditBox* CreateEditBox(HINSTANCE hInst, HWND hwnd, int pos_x, int pos_y, int width, int height);
};
#endif

SearchEditBox.cpp

#include "stdafx.h"
#include <windows.h>
#include <commctrl.h>
#include <richedit.h>
#include <string.h>
#include "SearchEditBox.h"
/*global vars*/
static LPCTSTR editBoxDefText = TEXT("Search...");
SearchEditBox::SearchEditBox()
{
firstPaint = false;
width = 0;
height = 0;
editBox = NULL;
}
SearchEditBox::~SearchEditBox()
{
if (editBox)
DestroyWindow(editBox);
}
void SearchEditBox::ChangeEdit(const bool change)
{
//...
}
HWND SearchEditBox::getEditBox()
{
return editBox;
}
SearchEditBox* SearchEditBox::CreateEditBox(HINSTANCE hInst, HWND hwnd, int pos_x, int pos_y, int width, int height)
{
// make sure RichEdit 4.1 is enabled
if (!GetModuleHandle(TEXT("Msftedit.dll")))
{
if (!LoadLibrary(TEXT("Msftedit.dll")))
{
MessageBox(NULL, L"Problem loading Msftedit.dll.", L"Error", 0);
return 0;
}
}
SearchEditBox *pSearchEditBox = new SearchEditBox;
pSearchEditBox->editBox = CreateWindowEx(0, MSFTEDIT_CLASS, editBoxDefText, WS_VISIBLE | WS_CHILD, pos_x + 6, pos_y + 4, width, height, hwnd, NULL, (HINSTANCE) GetWindowLong(hwnd, GWL_HINSTANCE), p_SearchEditBox);
if (!pSearchEditBox->editBox)
{
delete pSearchEditBox;
MessageBox(NULL, L"Problem creating the Search box.", L"Error", 0);
return 0;
}
if (!SetWindowSubclass(pSearchEditBox->editBox, SearchEditBox::EditBoxProc, 0, (DWORD_PTR)p_SearchEditBox))
{
delete pSearchEditBox;
MessageBox(NULL, L"Problem subclassing the Search box.", L"Error", 0);
return 0;
}
pSearchEditBox->width = width;
pSearchEditBox->height = height;
return pSearchEditBox;
}
LRESULT CALLBACK SearchEditBox::EditBoxProc(HWND hwnd, UINT uMsg, WPARAM wParam, LPARAM lParam, UINT_PTR uIdSubclass, DWORD_PTR dwRefData)
{
SearchEditBox *pSearchEditBox = (SearchEditBox*) dwRefData;
switch (uMsg)
{
case WM_NCDESTROY:
RemoveWindowSubclass(hwnd, SearchEditBox::EditBoxProc, uIdSubclass);
pSearchEditBox->editBox = NULL;
break;
case WM_SIZE:
pSearchEditBox->width = LOWORD(lParam);
pSearchEditBox->height = HIWORD(lParam);
break;
case WM_SETFOCUS:
{
TCHAR getText[10];
GetWindowText(hwnd, getText, 10);
if (_tcscmp(getText, editBoxDefText) == 0)
pSearchEditBox->ChangeEdit(true);
break;
}
case WM_KILLFOCUS:
{
TCHAR getText[10];
if (GetWindowText(hwnd, getText, 10) == 0)
pSearchEditBox->ChangeEdit(false);
break;
}
case WM_LBUTTONDBLCLK:
pSearchEditBox->ChangeEdit(true);
break;
case WM_PAINT:
{
if (!pSearchEditBox->firstPaint)
{
pSearchEditBox->firstPaint = true;
pSearchEditBox->ChangeEdit(false);
}
PAINTSTRUCT ps;
HDC hdc = BeginPaint(hwnd, &ps);
HBRUSH hBrush = CreateSolidBrush(RGB(33, 33, 33));
SelectObject(hdc, hBrush);
RoundRect(hdc, -6, -4, pSearchEditBox->width + 7, pSearchEditBox->height + 4, 5, 5);
EndPaint(hwnd, &ps);
break;
}
}
return DefSubclassProc(hwnd, uMsg, wParam, lParam);
}
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