我的C++程序將無法編譯後我關閉源然後再次打開它

Question

我編譯它，它運行，然後我重新打開它，不工作了。 這發生在devC++ 5.8.3和codeblocks中。

我的代碼（註釋是從IDE默認）：

#include <windows.h> 
    #include <cmath> 
    #include <cstdlib> 

    HPEN hPen; 
    HDC hDC; 
    PAINTSTRUCT Ps; 

    void DrawLine(int x1, int y1, int x2, int y2, HPEN pen){ 
     SelectObject(hDC,pen); 
     MoveToEx(hDC,x1,y1,NULL); 
     LineTo(hDC,x2,y2); 
    } 
    void Draw(int originx, int originy, float value,int handlength){ 
     DrawLine(originx, originy, (handlength*cos(value*180/3.14))+originx, (handlength*sin(value*180/3.14))+originy,hPen); 
     DrawLine(originx, originy, -(handlength*cos(value*180/3.14))+originx, -(handlength*sin(value*180/3.14))+originy,hPen); 
    } 
    /* This is where all the input to the window goes to */ 
    LRESULT CALLBACK WndProc(HWND hwnd, UINT Message, WPARAM wParam, LPARAM lParam) { 
     switch(Message) { 

      /* Upon destruction, tell the main thread to stop */ 
      case WM_DESTROY: { 
       PostQuitMessage(0); 
       break; 
      } 
      case WM_PAINT: { 
       int r; 
       int g; 
       int b; 
       hDC = BeginPaint(hwnd, &Ps); 
       for(int i=0;i<170;i=i+1){ 
       r = rand() % 256; 
       g = rand() % 256; 
       b = rand() % 256; 
       Sleep(10); 
       hPen = CreatePen(PS_INSIDEFRAME, 1, RGB(r, g, b)); 
       Draw(320,240,i,180); 

       }  
       EndPaint(hwnd, &Ps); 
       break; 
      } 
      /* All other messages (a lot of them) are processed using default procedures */ 
      default: 
       return DefWindowProc(hwnd, Message, wParam, lParam); 
     } 
     return 0; 
    } 

    /* The 'main' function of Win32 GUI programs: this is where execution starts */ 
    int WINAPI WinMain(HINSTANCE hInstance, HINSTANCE hPrevInstance, LPSTR lpCmdLine, int nCmdShow) { 
     WNDCLASSEX wc; /* A properties struct of our window */ 
     HWND hwnd; /* A 'HANDLE', hence the H, or a pointer to our window */ 
     MSG msg; /* A temporary location for all messages */ 

     /* zero out the struct and set the stuff we want to modify */ 
     memset(&wc,0,sizeof(wc)); 
     wc.cbSize  = sizeof(WNDCLASSEX); 
     wc.lpfnWndProc = WndProc; /* This is where we will send messages to */ 
     wc.hInstance  = hInstance; 
     wc.hCursor  = LoadCursor(NULL, IDC_ARROW); 

     /* White, COLOR_WINDOW is just a #define for a system color, try Ctrl+Clicking it */ 
     wc.hbrBackground = (HBRUSH)(COLOR_WINDOW+1); 
     wc.lpszClassName = "WindowClass"; 
     wc.hIcon   = LoadIcon(NULL, IDI_APPLICATION); /* Load a standard icon */ 
     wc.hIconSm  = LoadIcon(NULL, IDI_APPLICATION); /* use the name "A" to use the project icon */ 

     if(!RegisterClassEx(&wc)) { 
      MessageBox(NULL, "Window Registration Failed!","Error!",MB_ICONEXCLAMATION|MB_OK); 
      return 0; 
     } 

     hwnd = CreateWindowEx(WS_EX_CLIENTEDGE,"WindowClass","Lines",WS_VISIBLE|WS_OVERLAPPEDWINDOW, 
      CW_USEDEFAULT, /* x */ 
      CW_USEDEFAULT, /* y */ 
      640, /* width */ 
      480, /* height */ 
      NULL,NULL,hInstance,NULL); 

     if(hwnd == NULL) { 
      MessageBox(NULL, "Window Creation Failed!","Error!",MB_ICONEXCLAMATION|MB_OK); 
      return 0; 
     } 

     /* 
      This is the heart of our program where all input is processed and 
      sent to WndProc. Note that GetMessage blocks code flow until it receives something, so 
      this loop will not produce unreasonably high CPU usage 
     */ 
     while(GetMessage(&msg, NULL, 0, 0) > 0) { /* If no error is received... */ 
      TranslateMessage(&msg); /* Translate key codes to chars if present */ 
      DispatchMessage(&msg); /* Send it to WndProc */ 
     } 

     return msg.wParam; 
    } 

編譯器日誌：

• C++ Compiler: C:\Program Files (x86)\Dev-Cpp\MinGW64\bin\g++.exe
• Command: g++.exe "C:\Users\Pall\Desktop\proj1\lines.cpp" -o "C:\Users\Pall\Desktop\proj1\lines.exe" -g3 -I"C:\Program Files (x86)\Dev-Cpp\MinGW64\include" -I"C:\Program Files (x86)\Dev-Cpp\MinGW64\x86_64-w64-mingw32\include" -I"C:\Program Files (x86)\Dev-Cpp\MinGW64\lib\gcc\x86_64-w64-mingw32\4.8.1\include" -I"C:\Program Files (x86)\Dev-Cpp\MinGW64\lib\gcc\x86_64-w64-mingw32\4.8.1\include\c++" -L"C:\Program Files (x86)\Dev-Cpp\MinGW64\lib" -L"C:\Program Files (x86)\Dev-Cpp\MinGW64\x86_64-w64-mingw32\lib" -static-libgcc -g3 C:\Users\Pall\AppData\Local\Temp\ccRYW3Cy.o: In function DrawLine(int, int, int, int, HPEN__*)': C:/Users/Pall/Desktop/proj1/lines.cpp:12: undefined reference to __imp_SelectObject' C:/Users/Pall/Desktop/proj1/lines.cpp:13: undefined reference to __imp_MoveToEx' C:/Users/Pall/Desktop/proj1/lines.cpp:14: undefined reference to __imp_LineTo' C:\Users\Pall\AppData\Local\Temp\ccRYW3Cy.o: In function WndProc(HWND__*, unsigned int, unsigned long long, long long)': C:/Users/Pall/Desktop/proj1/lines.cpp:36: undefined reference to __imp_CreatePen' collect2.exe: error: ld returned 1 exit status

Answer 1

，這是造成的，因爲你需要鏈接庫libgdi32.a，如果你是使用DevC++，點擊Tools-> Compiler Options，打開窗口時，勾選「Add these commands to the linker command line」並在下面的文本框中添加文字：

-lgdi32 

你形成需要是這樣的：