Delphi XE4 64位中的SendMessageTimeout产生访问冲突 [英] SendMessageTimeout in Delphi XE4 64-bit produces Access violation

问题描述

我想在程序中广播一些环境变量的更改。因此，其他一些实用程序也可以使用新值。
当我在Windows 7平台上的32位Delphy XE4中编译下一个例程时，一切似乎都可以正常工作。
当我将Delphy切换到64位平台时，调试器会产生访问冲突。

I want to Broadcast the change of a few environment variables in my program. So a few other utilities can make use of the new values. When I compile the next routine in Delphy XE4 32-bit on a Windows 7 platform, everything seems to work fine. When I switch in Delphy to the 64-bit platform, the debugger produces an Access Violation.

有什么建议吗？

procedure BroadcastChange;
    var
        lParam, wParam : Integer;
        Buf : Array[0..10] of Char;
        aResult : PDWORD_PTR;
    begin
        Buf := 'Environment';
        wParam := 0;
        lParam := Integer(@Buf[0]);
        SendMessageTimeout(HWND_BROADCAST,
                           WM_SETTINGCHANGE,
                           wParam,
                           lParam,
                           SMTO_NORMAL,
                           4000,
                           aResult );
    end;

推荐答案

您需要将字符串终止为null。只需将声明切换为使用 PChar 。

You need to null terminate the string. Just switch the declaration to use a PChar.

您还必须停止将指针转换为32位 Integer 会将64位指针截断为32位指针，这很容易导致痛苦。

You must also stop casting pointers to 32 bit Integer which will truncate a 64 bit pointer to a 32 bit pointer, and that can easily lead to pain.

t使用aResult，传递nil。您的未初始化指针显然是一个问题。

Since you don't use aResult, pass nil. Your uninitialized pointer is obviously a problem.

procedure BroadcastChange;
begin
  SendMessageTimeout(
    HWND_BROADCAST, 
    WM_SETTINGCHANGE,
    0, 
    LPARAM(PChar('Environment')), 
    SMTO_NORMAL, 
    4000, 
    nil
  );
end;

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