windows程序设计 第九章 ENVIRON.C中的一个问题

#include <windows.h>#define ID_LISTBOX 1#define ID_TEXTBOX 2LRESULT CALLBACK WndProc (HWND, UINT, WPARAM, LPARAM) ;int WINAPI WinMain (HINSTANCE hInstance, HINSTANCE hPrevInstance,PSTR szCmdLine, int iCmdShow){static TCHAR szAppName[] = TEXT ("Environ") ;HWND hwnd ;MSG msg ;WNDCLASS wndclass ;wndclass.style = CS_HREDRAW | CS_VREDRAW ;wndclass.lpfnWndProc = WndProc ;wndclass.cbClsExtra = 0 ;wndclass.cbWndExtra = 0 ;wndclass.hInstance = hInstance ;wndclass.hIcon = LoadIcon (NULL, IDI_APPLICATION) ;wndclass.hCursor = LoadCursor (NULL, IDC_ARROW) ;wndclass.hbrBackground = (HBRUSH) (COLOR_WINDOW+1) ;wndclass.lpszMenuName = NULL ;wndclass.lpszClassName = szAppName ;if (!RegisterClass (&wndclass)){MessageBox ( NULL, TEXT ("This program requires Windows NT!"),szAppName, MB_ICONERROR) ;return 0 ;}hwnd = CreateWindow (szAppName, TEXT ("this is ENVIRON program"),WS_OVERLAPPEDWINDOW,CW_USEDEFAULT, CW_USEDEFAULT,CW_USEDEFAULT, CW_USEDEFAULT,NULL, NULL, hInstance, NULL) ;ShowWindow (hwnd, iCmdShow) ;UpdateWindow (hwnd) ;while (GetMessage (&msg, NULL, 0, 0)){TranslateMessage (&msg) ;DispatchMessage (&msg) ;}return msg.wParam ;}void FillListBox(HWND hwndList){int iLength1;TCHAR *pVarBlock,*pVarBeg,*pVarEnd,*pVarName,*pVarBlock1;pVarBlock=pVarBlock1=GetEnvironmentStrings();while(*pVarBlock){if(*pVarBlock != '='){pVarBeg=pVarBlock;while(*pVarBlock++ != '=');pVarEnd=pVarBlock-1;iLength1=pVarEnd-pVarBeg;pVarName=(TCHAR*)calloc(iLength1+1,sizeof(TCHAR));CopyMemory(pVarName,pVarBeg,iLength1*sizeof(TCHAR));pVarName[iLength1]='\0';SendMessage(hwndList,LB_ADDSTRING,0,(LPARAM)pVarName);free(pVarName);}while(*pVarBlock++ != '\0');}FreeEnvironmentStrings(pVarBlock1);}LRESULT CALLBACK WndProc(HWND hwnd,UINT message,WPARAM wParam,LPARAM lParam)  {  static HWND hwndList,hwndText;int cxChar,cyChar;int iLength,iIndex;TCHAR *pVarName1,*pVar;    switch(message){case WM_CREATE:cxChar=LOWORD(GetDialogBaseUnits());cyChar=HIWORD(GetDialogBaseUnits());hwndList=CreateWindow(TEXT("listbox"),NULL,WS_CHILD | WS_VISIBLE | LBS_STANDARD,cxChar,3*cyChar,16*cxChar,cyChar*10,hwnd,(HMENU) ID_LISTBOX,(HINSTANCE) GetWindowLong(hwnd,GWL_HINSTANCE),NULL);hwndText=CreateWindow(TEXT("static"),NULL,WS_CHILD | WS_VISIBLE | SS_LEFT,cxChar,cyChar,GetSystemMetrics(SM_CXSCREEN),cyChar,hwnd,(HMENU) ID_TEXTBOX,(HINSTANCE) GetWindowLong(hwnd,GWL_HINSTANCE),NULL);FillListBox(hwndList);return 0;case WM_SETFOCUS:SetFocus(hwndList);return 0;case WM_COMMAND:if(LOWORD(wParam)==ID_LISTBOX && HIWORD(wParam)==LBN_SELCHANGE){iIndex=SendMessage(hwndList,LB_GETCURSEL,0,0);iLength=SendMessage(hwndList,LB_GETTEXTLEN,iIndex,0)+1;pVarName1=(TCHAR*) calloc(iLength,sizeof(TCHAR));SendMessage(hwndList,LB_GETTEXT,iIndex,(LPARAM)pVarName1);iLength=GetEnvironmentVariable(pVarName1,NULL,0);pVar=(TCHAR*) calloc(iLength,sizeof(TCHAR));GetEnvironmentVariable(pVarName1,pVar,iLength);SetWindowText(hwndText,pVar);free (pVarName1);free (pVar);}return 0;case WM_DESTROY:PostQuitMessage(0);return 0;}return DefWindowProc(hwnd,message,wParam,lParam);} 

笔者按照书中的代码调试（F5）总是出现

“ Windows 已在 ENVIRON1.exe 中触发一个断点。其原因可能是堆被损坏，这说明 ENVIRON1.exe 中或它所加载的任何 DLL 中有 Bug。。”

这个应该内存释放出现了问题，检查发现书中代码在

FreeEnvironmentStrings(pVarBlock);

有问题，因为pVarBlock在

while(*pVarBlock++ != '=');

while(*pVarBlock++ != '\0');

值已经改变了，不能利用该指针进行内存释放，本文中利用pVarBlock1进行内存的释放。

另注：

运行本程序时，总是出现“LINK : fatal error LNK1123: 转换到 COFF 期间失败: 文件无效或损坏”这个问题，网上已有解决方案：项目\属性\配置属性\清单工具\输入和输出\嵌入清单：原来是“是”，改成“否”。不过每次创建新项目总是要重新设置一遍。