关于《Windows程序设计（第五版）》中一个实例程序的疑问-白红宇

关于《Windows程序设计（第五版）》中一个实例程序的疑问

阅读量：4655 次

发布时间：2019-06-09

本文共 5341 字，大约阅读时间需要 17 分钟。

最近一直在看Charlse Petzold的《Windows程序设计》，作为一个新得不能再新的新手，只能先照着书的抄抄源码了，之前的例子一直都很正常，但昨天遇到一个很诡异的BUG。

先看实例源码吧：

1 /*-----------------------------------------------------------------  2         ENVIRON.C -- Environment List Box  3         (c) Charles Petzold,1998  4         Copy by XXXX,2015/1/26  5 ------------------------------------------------------------------*/  6   7 #include 
     
        8   9 #define ID_LIST 1 10 #define ID_TEXT 2 11  12 LRESULT CALLBACK WndProc(HWND hwnd, UINT, WPARAM, LPARAM); 13  14 int WINAPI WinMain(HINSTANCE hInstance, HINSTANCE hPrevInstance, PSTR szCmdLine, int iCmdShow) 15 { 16     static TCHAR szAppName[] = TEXT("Environ"); 17     HWND hwnd; 18     MSG msg; 19     WNDCLASS wndclass; 20  21     wndclass.style = CS_VREDRAW | CS_HREDRAW; 22     wndclass.lpfnWndProc = WndProc; 23     wndclass.cbClsExtra = 0; 24     wndclass.cbWndExtra = 0; 25     wndclass.hInstance = hInstance; 26     wndclass.hIcon = LoadIcon(NULL, IDI_APPLICATION); 27     wndclass.hCursor = LoadCursor(NULL, IDC_ARROW); 28     wndclass.hbrBackground = (HBRUSH)GetStockObject(WHITE_BRUSH); 29     wndclass.lpszMenuName = NULL; 30     wndclass.lpszClassName = szAppName; 31  32     if (!RegisterClass(&wndclass)) 33     { 34         MessageBox(NULL, TEXT("This program requires Windows NT!"), szAppName, MB_ICONERROR); 35         return 0; 36     } 37  38     hwnd = CreateWindow(szAppName, TEXT("Environment List Box"), WS_OVERLAPPEDWINDOW, 39         CW_USEDEFAULT, CW_USEDEFAULT, CW_USEDEFAULT, CW_USEDEFAULT, NULL, NULL, hInstance, NULL); 40     ShowWindow(hwnd, iCmdShow); 41     UpdateWindow(hwnd); 42  43     while (GetMessage(&msg, NULL, 0, 0)) 44     { 45         TranslateMessage(&msg); 46         DispatchMessage(&msg); 47     } 48     return msg.wParam; 49 } 50  51  52 void FillListBox(HWND hwndList) 53 { 54     int iLength; 55     TCHAR * pVarBlock, *pVarBeg, *pVarEnd, *pVarName; 56     pVarBlock = GetEnvironmentStrings();    //Get pointer to environment block 57  58     while (*pVarBlock) 59     { 60         if (*pVarBlock != '=')    //Skip variable names begining with '=' 61         { 62             pVarBeg = pVarBlock;    //Beging of variable name 63             while (*(pVarBlock++) != '=');    //Scan until '=' 64             pVarEnd = pVarBlock - 1;    //Points to '=' sign 65             iLength = pVarEnd - pVarBeg;    //Length of variable name 66  67             //Allocate memory for the variable name and terminating 68             //zero.Copy the variable name and append a zero 69             pVarName = calloc(iLength + 1, sizeof(TCHAR)); 70             CopyMemory(pVarName, pVarBeg, iLength * sizeof(TCHAR)); 71             pVarName[iLength] = '\0'; 72  73             //Put the variable name int the list box and free memory 74             SendMessage(hwndList, LB_ADDSTRING, 0, (LPARAM)pVarName); 75             free(pVarName); 76         } 77         while (*pVarBlock++ != '\0');    //Scna until terminating zero 78  79     } 80     FreeEnvironmentStrings(pVarBlock);     81     int code; 82     code = GetLastError(); 83 } 84  85  86 LRESULT CALLBACK WndProc(HWND hwnd, UINT message, WPARAM wParam, LPARAM lParam) 87 { 88     static HWND hwndList, hwndText; 89     int iIndex, iLength, cxChar, cyChar; 90     TCHAR * pVarName, *pVarValue; 91  92     switch (message) 93     { 94     case WM_CREATE: 95         cxChar = LOWORD(GetDialogBaseUnits()); 96         cyChar = HIWORD(GetDialogBaseUnits()); 97  98         //Create listbox and static text windows 99         hwndList = CreateWindow(TEXT("listbox"), NULL, WS_CHILD | WS_VISIBLE | LBS_STANDARD,100             cxChar, cyChar * 3, cxChar * 16 + GetSystemMetrics(SM_CXVSCROLL), cyChar * 5, hwnd,101             (HMENU)ID_LIST, (HINSTANCE)GetWindowLong(hwnd, GWL_HINSTANCE), NULL);102         hwndText = CreateWindow(TEXT("static"), NULL, WS_CHILD | WS_VISIBLE | SS_LEFT, cxChar, cyChar,103             GetSystemMetrics(SM_CXSCREEN), cyChar, hwnd, (HMENU)ID_TEXT,104             (HINSTANCE)GetWindowLong(hwnd, GWL_HINSTANCE), NULL);105         FillListBox(hwndList);106         return 0;107 108 109     case WM_SETFOCUS:110         SetFocus(hwndList);111         return 0;112 113 114     case WM_COMMAND:115         if (LOWORD(wParam) == ID_LIST&&HIWORD(wParam) == LBN_SELCHANGE)116         {117             //Get current selectiong118             iIndex = SendMessage(hwndList, LB_GETCURSEL, 0, 0);119             iLength = SendMessage(hwndList, LB_GETTEXTLEN, iIndex, 0) + 1;120             pVarName = calloc(iLength, sizeof(TCHAR));121             SendMessage(hwndList, LB_GETTEXT, iIndex, (LPARAM)pVarName);122 123             //Get environment string124             iLength = GetEnvironmentVariable(pVarName, NULL, 0);125             pVarValue = calloc(iLength, sizeof(TCHAR));126             GetEnvironmentVariable(pVarName, pVarValue, iLength);127 128             //Show it in window129             SetWindowText(hwndText, pVarValue);130             free(pVarName);131             free(pVarValue);132         }133         return 0;134 135 136     case WM_DESTROY:137         PostQuitMessage(0);138         return 0;139     }140     return DefWindowProc(hwnd, message, wParam, lParam);141 }

编译什么的都没有错误提示，但是在本地调试时提示触发一个断点，但是我确定我没有下过断点！！！

提示如图：