SDL2 Linking errors? Undefined reference to SDL_main

Question

I am trying to figure out how to use SDL2 on VSCODE. I've got basic code and windows working but when I add additional functions and files, it doesn't seem to want to compile. I'm new to this but I thought I included the necessary things in my headers and in my build.

For the main

#include "../include/SDL2/SDL.h"
#include "assets/cleanup.h"
#include "assets/res_path.h"
#include "assets/drawing_functions.h"
#include "../include/SDL2/SDL_mixer.h"
#include <iostream>

For the build.bat I have

    g++ -Isrc/include -Lsrc/lib -o main main.cpp -lmingw32 -lSDL2main -lSDL2
    g++ -Isrc/include -Lsrc/lib -o cleanup assets/cleanup.cpp -lmingw32 -lSDL2main -lSDL2
    g++ -Isrc/include -Lsrc/lib -o drawing_functions assets/drawing_functions.cpp -lmingw32 -lSDL2main -lSDL2
    g++ -Isrc/include -Lsrc/lib -o res_path assets/res_path.cpp -lmingw32 -lSDL2main -lSDL2
    g++ -Isrc/include -Lsrc/lib -o randomNumber assets/randomNumber.cpp -lmingw32 -lSDL2main -lSDL2

note: it works just fine without the additional cpp files. If I just had main and deleted my additions it'd run fine. I'm wondering whats causing it to break.

For res_path

#include <iostream>
#include <string>
#include "../include/SDL2/SDL.h"

for random_number its just ctime and cstdlib

for drawingfunctions

#include <iostream>
#include "../include/SDL2/SDL.h"
#include "../include/SDL2/SDL_image.h"
#include "../include/SDL2/SDL_ttf.h"
#include "res_path.h"
#include "cleanup.h"

Finally for cleanup

#include <utility>
#include "../include/SDL2/SDL.h"

Here are the errors that I've been trying to debug

Errors as text:

C:\Users\PC\Desktop\C++Projects\2D Game>g++ -Isrc/include -Lsrc/lib -o main main.cpp -lmingw32 -lSDL2main -lSDL2
C:\Users\PC\AppData\Local\Temp\ccOXUYZZ.o:main.cpp:(.text+0x92): undefined reference to `cleanup(SDL_Window*)'
C:\Users\PC\AppData\Local\Temp\ccOXUYZZ.o:main.cpp:(.text+0x145): undefined reference to `IMG_Init'
C:\Users\PC\AppData\Local\Temp\ccOXUYZZ.o:main.cpp:(.text+0x18b): undefined reference to `TTF_Init'
C:\Users\PC\AppData\Local\Temp\ccOXUYZZ.o:main.cpp:(.text+0x1ec): undefined reference to `Mix_OpenAudio'
C:\Users\PC\AppData\Local\Temp\ccOXUYZZ.o:main.cpp:(.text+0x261): undefined reference to `getResourcePath(std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> > const&)'  
C:\Users\PC\AppData\Local\Temp\ccOXUYZZ.o:main.cpp:(.text+0x2a1): undefined reference to `loadTexture(std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> > const&, SDL_Renderer*)'
C:\Users\PC\AppData\Local\Temp\ccOXUYZZ.o:main.cpp:(.text+0x2f4): undefined reference to `renderTexture(SDL_Texture*, SDL_Renderer*, int, int, SDL_Rect*)'
C:\Users\PC\AppData\Local\Temp\ccOXUYZZ.o:main.cpp:(.text+0x30c): undefined reference to `cleanup(SDL_Renderer*)'
C:\Users\PC\AppData\Local\Temp\ccOXUYZZ.o:main.cpp:(.text+0x317): undefined reference to `cleanup(SDL_Window*)'
C:\Users\PC\AppData\Local\Temp\ccOXUYZZ.o:main.cpp:(.text+0x322): undefined reference to `cleanup(SDL_Texture*)'
collect2.exe: error: ld returned 1 exit status

C:\Users\PC\Desktop\C++Projects\2D Game>g++ -Isrc/include -Lsrc/lib -o cleanup assets/cleanup.cpp -lmingw32 -lSDL2main -lSDL2
src/lib/libSDL2main.a(SDL_windows_main.o): In function `main_getcmdline':
/Users/valve/release/SDL/SDL2-2.0.14-source/foo-x86/../src/main/windows/SDL_windows_main.c:71: undefined reference to `SDL_main'
collect2.exe: error: ld returned 1 exit status

C:\Users\PC\Desktop\C++Projects\2D Game>g++ -Isrc/include -Lsrc/lib -o drawing_functions assets/drawing_functions.cpp -lmingw32 -lSDL2main -lSDL2
C:\Users\PC\AppData\Local\Temp\ccSkQs61.o:drawing_functions.cpp:(.text+0x19): undefined reference to `IMG_LoadTexture'
C:\Users\PC\AppData\Local\Temp\ccSkQs61.o:drawing_functions.cpp:(.text+0x62): undefined reference to `IMG_Load'
C:\Users\PC\AppData\Local\Temp\ccSkQs61.o:drawing_functions.cpp:(.text+0x108): undefined reference to `cleanup(SDL_Surface*)'
C:\Users\PC\AppData\Local\Temp\ccSkQs61.o:drawing_functions.cpp:(.text+0x1ea): undefined reference to `TTF_OpenFont'
C:\Users\PC\AppData\Local\Temp\ccSkQs61.o:drawing_functions.cpp:(.text+0x242): undefined reference to `TTF_RenderText_Blended'
C:\Users\PC\AppData\Local\Temp\ccSkQs61.o:drawing_functions.cpp:(.text+0x256): undefined reference to `TTF_CloseFont'
C:\Users\PC\AppData\Local\Temp\ccSkQs61.o:drawing_functions.cpp:(.text+0x2d8): undefined reference to `TTF_CloseFont'
C:\Users\PC\AppData\Local\Temp\ccSkQs61.o:drawing_functions.cpp:(.text+0x338): undefined reference to `TTF_RenderText_Blended'
src/lib/libSDL2main.a(SDL_windows_main.o): In function `main_getcmdline':
/Users/valve/release/SDL/SDL2-2.0.14-source/foo-x86/../src/main/windows/SDL_windows_main.c:71: undefined reference to `SDL_main'
collect2.exe: error: ld returned 1 exit status

C:\Users\PC\Desktop\C++Projects\2D Game>g++ -Isrc/include -Lsrc/lib -o res_path assets/res_path.cpp -lmingw32 -lSDL2main -lSDL2
src/lib/libSDL2main.a(SDL_windows_main.o): In function `main_getcmdline':
/Users/valve/release/SDL/SDL2-2.0.14-source/foo-x86/../src/main/windows/SDL_windows_main.c:71: undefined reference to `SDL_main'
collect2.exe: error: ld returned 1 exit status

C:\Users\PC\Desktop\C++Projects\2D Game>g++ -Isrc/include -Lsrc/lib -o randomNumber assets/randomNumber.cpp -lmingw32 -lSDL2main -lSDL2
src/lib/libSDL2main.a(SDL_windows_main.o): In function `main_getcmdline':
/Users/valve/release/SDL/SDL2-2.0.14-source/foo-x86/../src/main/windows/SDL_windows_main.c:71: undefined reference to `SDL_main'
collect2.exe: error: ld returned 1 exit status

Answer 1

You can use g++ to build your program in two ways:

• In two stages, first by compiling the individual .cpp files as translation units to object files .o and then in another invocation of g++ to link them together into an executable

• Or you can use a single invocation of g++ to compile and link the executable.

You are currently trying to mix the two modes somehow. For the single-invocation build you should call g++ only once and add all .cpp files to it:

g++ -Isrc/include -Lsrc/lib -o my_program main.cpp assets/cleanup.cpp assets/drawing_functions.cpp [...] -lmingw32 -lSDL2main -lSDL2

This will output the program with the file name my_program .

Your current build commands build multiple independent executables, each one containing only one of the .cpp files as a translation unit.