main function not being detected when compiled - c++

Question

I am trying to run a program that opens a window. the purpose is to get the program started opening a window is the start of all programs right?
But when I run my code for some reason I get this error:
Undefined symbols for architecture x86_64:
"_main", referenced from:
implicit entry/start for main executable
ld: symbol(s) not found for architecture x86_64
clang: error: linker command failed with exit code 1 (use -v to see invocation)
However, in my code I do have the main() function so why am I getting this error?
This is my code:
#include <SDL2/SDL.h>
#include <SDL2_image/SDL_image.h>
#include <SDL2_ttf/SDL_ttf.h>
#include <stdio.h>
int main(){
if(SDL_Init( SDL_INIT_EVERYTHING ) < 0){
std::cout << "error 1\n";
std::cout << SDL_GetError();
std::cout << "\n";
return -1;
}
if(TTF_Init() < 0){
std::cout << "error 2\n";
std::cout << TTF_GetError();
std::cout << "\n";
return -1;
}
SDL_Window* window = SDL_CreateWindow("test", 0, 0, 500, 500, 0);
if(!window){
std::cout << "error 3\n";
std::cout << SDL_GetError();
std::cout << "\n";
return -1;
}
int windowid = SDL_GetWindowID(window);
SDL_Renderer* Renderer = SDL_CreateRenderer(window, -1, 0);
running = true;
SDL_Event event;
while(running){
while(SDL_PollEvent(&event)){
if(event.type == SDL_WindowEvent){
if(event.window.windowID == windowid){
if(event.window.type == SDL_WindowClose){
Destroywindow(window);
running = false;
}
}
}
}
}
return 0;
}
my make file looks like this:
#!/bin/bash
brew update
brew install sdl2
g++ -o /Users/mikahshattuck/noneproject/none2019-05-0909-22-
14:2:/none.app/Contents/MacOS/mainrun.cpp -I /Library/Frameworks -l
SDL2
exit 0
this is the full out:
Already up-to-date.
Warning: sdl2 2.0.9_1 is already installed and up-to-date
To reinstall 2.0.9_1, run `brew reinstall sdl2`
Undefined symbols for architecture x86_64:
"_main", referenced from:
implicit entry/start for main executable
ld: symbol(s) not found for architecture x86_64
clang: error: linker command failed with exit code 1 (use -v to see
invocation)
logout
Saving session...
...copying shared history...
...saving history...truncating history files...
...completed.
[Process completed]
thank you in advance

Answer 1

When using SDL on macOS or Windows, you need to add -Dmain=SDL_main to your compile flags and -lSDL2main to your link flags. Since you're using Homebrew, you can make it easier and just use pkg-config to get the correct flags. Use this compiler command as a template and adapt it to your needs:
g++ $(pkg-config --cflags sdl2) -I /Library/Frameworks source.cpp -o output_executable $(pkg-config --libs sdl2)
However, it seems you are also using SDL_ttf, not just plain SDL. In this case, you should probably use SDL2_ttf instead of sdl2 as the package argument of pkg-config:
g++ $(pkg-config --cflags SDL2_ttf) -I /Library/Frameworks source.cpp -o output_executable $(pkg-config --libs SDL2_ttf)
The SDL2_ttf package depends on the sdl2 package, so using SDL2_ttf will also emit the needed flags for sdl2.
The names of the pkg-config packages correspond to *.pc files installed by Homebrew into /usr/local/lib/pkgconfig.