CODEWITHSUNDEEP
c++program-entry-point
Mikah
Mikah

Reputation: 326

main function not being detected when compiled

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

Upvotes: 4

Views: 247

Answers (1)

Nikos C.
Nikos C.

Reputation: 51930

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.

Upvotes: 4

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