编译后链接器错误

Question

Im having a problem with the linker i guess

This is what i get on the output tab:

1>main-light.obj : error LNK2019: unresolved external symbol _SDL_FreeSurface referenced in function "private: unsigned int __thiscall objloader::loadTexture(char const *)" (?loadTexture@objloader@@AAEIPBD@Z)
1>main-light.obj : error LNK2019: unresolved external symbol _SDL_LoadBMP_RW referenced in function "private: unsigned int __thiscall objloader::loadTexture(char const *)" (?loadTexture@objloader@@AAEIPBD@Z)
1>main-light.obj : error LNK2019: unresolved external symbol _SDL_RWFromFile referenced in function "private: unsigned int __thiscall objloader::loadTexture(char const *)" (?loadTexture@objloader@@AAEIPBD@Z)
1>main-light.obj : error LNK2019: unresolved external symbol _SDL_GetTicks referenced in function "public: void __thiscall Player::init(void)" (?init@Player@@QAEXXZ)
1>main-light.obj : error LNK2019: unresolved external symbol _SDL_GetKeyState referenced in function "void __cdecl Control(float,float,bool)" (?Control@@YAXMM_N@Z)
1>main-light.obj : error LNK2019: unresolved external symbol _SDL_WarpMouse referenced in function "void __cdecl Control(float,float,bool)" (?Control@@YAXMM_N@Z)
1>main-light.obj : error LNK2019: unresolved external symbol _SDL_GetMouseState referenced in function "void __cdecl Control(float,float,bool)" (?Control@@YAXMM_N@Z)
1>main-light.obj : error LNK2019: unresolved external symbol _SDL_ShowCursor referenced in function "void __cdecl Control(float,float,bool)" (?Control@@YAXMM_N@Z)
1>main-light.obj : error LNK2019: unresolved external symbol _SDL_Delay referenced in function _SDL_main
1>main-light.obj : error LNK2019: unresolved external symbol _SDL_GL_SwapBuffers referenced in function _SDL_main
1>main-light.obj : error LNK2019: unresolved external symbol _SDL_PollEvent referenced in function _SDL_main
1>main-light.obj : error LNK2019: unresolved external symbol _SDL_SetVideoMode referenced in function _SDL_main
1>main-light.obj : error LNK2019: unresolved external symbol _SDL_Init referenced in function _SDL_main
1>MSVCRT.lib(crtexe.obj) : error LNK2019: unresolved external symbol _main referenced in function ___tmainCRTStartup
1>C:\Users\Tiago\Desktop\Projects\FPS\Debug\FPS.exe : fatal error LNK1120: 14 unresolved externals

here is the command line of the linker (if it can help you...):

/OUT:"C:\Users\Tiago\Desktop\Projects\FPS\Debug\FPS.exe" /NOLOGO "SDL.lib" "SDLmain.lib" "glu32.lib" "glut32.lib" "opengl32.lib" "kernel32.lib" "user32.lib" "gdi32.lib" "winspool.lib" "comdlg32.lib" "advapi32.lib" "shell32.lib" "ole32.lib" "oleaut32.lib" "uuid.lib" "odbc32.lib" "odbccp32.lib" /MANIFEST /ManifestFile:"Debug\FPS.exe.intermediate.manifest" /ALLOWISOLATION /MANIFESTUAC:"level='asInvoker' uiAccess='false'" /DEBUG /PDB:"C:\Users\Tiago\Desktop\Projects\FPS\Debug\FPS.pdb" /SUBSYSTEM:CONSOLE /PGD:"C:\Users\Tiago\Desktop\Projects\FPS\Debug\FPS.pgd" /TLBID:1 /DYNAMICBASE /NXCOMPAT /MACHINE:X86 /ERRORREPORT:QUEUE 

More information: i've put the OpenGL and SDL folder (the folder with the include and lib files) in the main folder of my project. Is it causing the problem?

Answer 1

I cannot find anything relevant in the SDL docs on how to configure your project properly. The header files gives some hints, it uses non-standard #defines to select the platform. Which explains the first set of linker errors, the DECLSPEC macro has to be set correctly. For some really mysterious reason it wants to rename main() as well, the reason for your last linker error. No clue why any of this is necessary, these kind of hacks tend to be used as a filter. As in, "can't figure this out by yourself, don't bug us with your other questions".

First thing you have to do: right-click your project, Properties, Linker, Advanced, Entry Point = SDL_main. Make your code look similar to this, I hard-coded the paths and told the linker what to link:

include "stdafx.h"
#define __WIN32__    // Non-standard define to select the platform
#include "c:/temp/sdl-1.2.15/include/sdl.h"
#pragma comment(lib, "c:/temp/sdl-1.2.15/lib/x86/sdl.lib")


int main(int argc, char* argv[])
{
    SDL_Init(SDL_INIT_EVERYTHING);   // Just an example
    // etc...
    return 0;
}

It linked correctly, that's all I tried. Running it requires sdl.dll in the same directory as your .exe. Good luck with it, sounds like you'll need it.