关于内存分配失败的问题

Question

if (ptlvitem = nil)or(p_MyItemText = nil) then begin
    MessageBox(0,'error memory!','error!',0);//不怎么乍执行到这里了，请各位前辈指点。procedure SetListView(hwnd:THandle);
    var
        lvitem:TLVITEM;
        ptlvitem:PLVITEM;
PID:LongInt;
hProcess:THandle;
p_MyItemText:pchar;//目标程序中用来存放TEXT的地址
        str_MyItemText:Array[0..12] of char;
    begin
        //strcpy(str_MyItemText,"300");
        if (hwnd=0) then begin
            MessageBox(0,'error hwnd','error!',0);
        end else begin
            GetWindowThreadProcessId(hwnd, @PID);
            hProcess:=OpenProcess(PROCESS_ALL_ACCESS,false,PID);
            if (hProcess=0) then begin
                MessageBox(0,'error hProcess!','error!',0);
            end else begin
                ptlvitem:=PLVITEM(VirtualAllocEx(hProcess, nil, SizeOf(TLVITEM), MEM_COMMIT, PAGE_READWRITE));
p_MyItemText:=pchar(VirtualAllocEx(hProcess, nil, 12, MEM_COMMIT, PAGE_READWRITE));
                if (ptlvitem = nil)or(p_MyItemText = nil) then begin
                   MessageBox(0,'error memory!','error!',0);//不怎么乍执行到这里了，请各位前辈指点。
                end else begin
                   str_MyItemText:=Form1.Edit10.Text;
                   lvitem.iSubItem:=1;
   lvitem.pszText:=p_MyItemText;
                   WriteProcessMemory(hProcess, p_MyItemText, Pointer(@str_MyItemText), 1024, nil);
   WriteProcessMemory(hProcess, ptlvitem, Pointer(@lvitem), SizeOf(TLVITEM), nil);
                   SendMessage(hwnd, LVM_SETITEMTEXT, 4, LongInt(ptlvitem));
                end;
            end;
        end;
    end;  

Answer 1

我又另开了一个Demo工程，也还是同样的问题。请各位前辈帮忙看看哦。谢谢！
implementation
  function VirtualAllocEx(hProcess:THANDLE;
                          lpAddress:LPVOID;
                          dwSize:DWORD ;
                          flAllocationType : DWORD;
                          flProtect : DWORD):POINTER;
                          external 'kernel32' name 'VirtualAllocEx';
  function VirtualFreeEx(hProcess:THANDLE;
                         lpAddress:LPVOID;
                         dwSize:DWORD ;
                         dwFreeType : DWORD):WINBOOL;
                         external 'kernel32' name 'VirtualFreeEx';
{ TForm1 }procedure TForm1.Button1Click(Sender: TObject);
var
   {HWND hwnd;
int iItem=0;
LVITEM lvitem, *plvitem;
DWORD PID;
HANDLE hProcess;
char *p_MyItemText;//目标程序中用来存放TEXT的地址
}
    hwnd:THandle;
    livtem:TLVITEM;
    pivtem:PLVITEM;
    PID:LongWord;
    hProcess:THandle;
    p_MyItemText:pchar;
    str_MyItemText:Array[0..12] of char;
begin
    hwnd:=THandle(395556);
    if (hwnd=0) then begin
MessageBox(0,'Error hwnd','Error',0);
    end else begin
        GetWindowThreadProcessId(hwnd, @PID);
        hProcess:=OpenProcess(PROCESS_ALL_ACCESS,false,PID);
        if (hProcess=0) then begin
   MessageBox(0,'Error hProcess','Error',0);
        end else begin
           pivtem:=VirtualAllocEx(hProcess,nil, sizeof(TLVITEM), $1000{MEM_COMMIT}, PAGE_READWRITE);
   p_MyItemText:=VirtualAllocEx(hProcess, nil, 12, $1000{MEM_COMMIT}, PAGE_READWRITE);
           if(pivtem=nil) or (p_MyItemText=nil) then begin
              MessageBox(0,'Error Memory','Error',0);
           end else begin           end;
        end;
    end;
end;    

Answer 2

pivtem
p_MyItemText
依然为nil,为何呢，我这是从一个C代码转换过来的。
C代码如下
/*
 * Send LVM_SETITEMTEXT
 * 版权所有 (C) 2005 天津 赵春生
 * 2005.10.28
 * http://timw.yeah.net
 * http://timw.126.com
 * 本程序适用于:Win2KP+SP4[Windows TaskManager(5.0.2195.6620)]
 *  WinXP+SP1[Windows TaskManager]
 * 代码在Win2000P+SP4 + VC6+SP6测试通过
*/
#include<windows.h>
#include<commctrl.h>int APIENTRY WinMain(HINSTANCE hInstance,
                     HINSTANCE hPrevInstance,
                     LPSTR     lpCmdLine,
                     int       nCmdShow)
 
{

HWND hwnd;
int iItem=0;
LVITEM lvitem, *plvitem;
DWORD PID;
HANDLE hProcess;
char *p_MyItemText;//目标程序中用来存放TEXT的地址 //The pszText member is the pointer to a null-terminated
//  string containing the new text; it can also be NULL.
//以上信息是从API手册中获得的，故在本例中字符串长度不能>=12，
//以确保字符串后有NULL。
char str_MyItemText[12]={0};
strcpy(str_MyItemText,"300");


//hwnd=FindWindow("#32770","Windows 任务管理器");
//hwnd=FindWindow("Fiber Trace",NULL);
//hwnd=FindWindowEx(hwnd,0,"Fiber Trace",0);
hwnd=(HWND)132668; if (!hwnd)

MessageBox(NULL,"[Windows 任务管理器] 尚未启动！","错误！",NULL);

else
{ GetWindowThreadProcessId(hwnd, &PID);

hProcess=OpenProcess(PROCESS_ALL_ACCESS,false,PID);
if (!hProcess)

MessageBox(NULL,"获取进程句柄操作失败！","错误！",NULL);

else
{
plvitem=(LVITEM*)VirtualAllocEx(hProcess, NULL, sizeof(LVITEM), MEM_COMMIT, PAGE_READWRITE);
p_MyItemText=(char*)VirtualAllocEx(hProcess, NULL, 12, MEM_COMMIT, PAGE_READWRITE); if ((!plvitem)||(!p_MyItemText))

MessageBox(NULL,"无法分配内存！","错误！",NULL);

else
{
MessageBox(NULL,"本演示程序将更改TaskManager中第6个项目中第1列的内容。","提示",NULL);

iItem=5;//5在这里是第六个（从零开始）
lvitem.iSubItem=1;//同上
lvitem.pszText=p_MyItemText;

WriteProcessMemory(hProcess, p_MyItemText, &str_MyItemText, 12, NULL);
WriteProcessMemory(hProcess, plvitem, &lvitem, sizeof(LVITEM), NULL); //向目标程序发送LVM_SETITEMTEXT消息
SendMessage(hwnd, LVM_SETITEMTEXT, (WPARAM)iItem, (LPARAM)plvitem);

}
}
}




//释放内存
CloseHandle(hwnd);
CloseHandle(hProcess);
VirtualFreeEx(hProcess, plvitem, 0, MEM_RELEASE);
VirtualFreeEx(hProcess, p_MyItemText, 0, MEM_RELEASE);

return 0;
}

Answer 3

终于解决了，原来问题在于参数传递规则上。如下解决,只加上stdcall就可以了。
function VirtualAllocEx(hProcess:HANDLE;
                          lpAddress:LPVOID;
                          dwSize:DWORD ;
                          flAllocationType : DWORD;
                          flProtect : DWORD):POINTER; stdcall;
                          external 'kernel32' name 'VirtualAllocEx';
  function VirtualFreeEx(hProcess:HANDLE;
                         lpAddress:LPVOID;
                         dwSize:DWORD ;
                         dwFreeType : DWORD):WINBOOL;stdcall;
                         external 'kernel32' name 'VirtualFreeEx';