Error multiple definition when compiling using headers [closed] - c++

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I am having a lot of trouble with my header files and the compilation. I have everything linked with header guards but for some reason I am still getting a lot of multiple definition errors. I'm also look for help on better way to organize code. Whatever help is appreciated!
This is the out output of my console when I do the g++ call:
g++ main.cpp close.cpp init.cpp load_media.cpp texture.cpp -w -lSDL2 -lSDL2_image -lSDL2_mixer -lSDL2_ttf -o run
/tmp/cc3oNgPs.o:(.bss+0x0): multiple definition of `g_font'
/tmp/ccg0hCKW.o:(.bss+0x0): first defined here
/tmp/cc3oNgPs.o:(.bss+0x8): multiple definition of `g_window'
/tmp/ccg0hCKW.o:(.bss+0x8): first defined here
/tmp/cc3oNgPs.o:(.bss+0x10): multiple definition of `g_renderer'
/tmp/ccg0hCKW.o:(.bss+0x10): first defined here
/tmp/cc3oNgPs.o:(.bss+0x20): multiple definition of `g_text_texture'
/tmp/ccg0hCKW.o:(.bss+0x20): first defined here
/tmp/ccIgzhbZ.o:(.bss+0x0): multiple definition of `g_font'
/tmp/ccg0hCKW.o:(.bss+0x0): first defined here
/tmp/ccIgzhbZ.o:(.bss+0x8): multiple definition of `g_window'
/tmp/ccg0hCKW.o:(.bss+0x8): first defined here
/tmp/ccIgzhbZ.o:(.bss+0x10): multiple definition of `g_renderer'
/tmp/ccg0hCKW.o:(.bss+0x10): first defined here
/tmp/ccIgzhbZ.o:(.bss+0x20): multiple definition of `g_text_texture'
/tmp/ccg0hCKW.o:(.bss+0x20): first defined here
/tmp/ccQs9gPv.o:(.bss+0x0): multiple definition of `g_font'
/tmp/ccg0hCKW.o:(.bss+0x0): first defined here
/tmp/ccQs9gPv.o:(.bss+0x8): multiple definition of `g_window'
/tmp/ccg0hCKW.o:(.bss+0x8): first defined here
/tmp/ccQs9gPv.o:(.bss+0x10): multiple definition of `g_renderer'
/tmp/ccg0hCKW.o:(.bss+0x10): first defined here
/tmp/ccQs9gPv.o:(.bss+0x20): multiple definition of `g_text_texture'
/tmp/ccg0hCKW.o:(.bss+0x20): first defined here
/tmp/ccxzUgM2.o:(.bss+0x0): multiple definition of `g_font'
/tmp/ccg0hCKW.o:(.bss+0x0): first defined here
/tmp/ccxzUgM2.o:(.bss+0x8): multiple definition of `g_window'
/tmp/ccg0hCKW.o:(.bss+0x8): first defined here
/tmp/ccxzUgM2.o:(.bss+0x10): multiple definition of `g_renderer'
/tmp/ccg0hCKW.o:(.bss+0x10): first defined here
/tmp/ccxzUgM2.o:(.bss+0x20): multiple definition of `g_text_texture'
/tmp/ccg0hCKW.o:(.bss+0x20): first defined here
collect2: error: ld returned 1 exit status
here are my 2 header files:
isolation.h
//include //include guard
#ifndef ISOLATION_H
#define ISOLATION_H
//include dependencies
#include <SDL2/SDL.h>
#include <SDL2/SDL_image.h>
#include <SDL2/SDL_ttf.h>
#include <stdio.h>
#include <string>
//include headers
#include "texture.h"
//Screen dimension constants
const int SCREEN_WIDTH = 1280;
const int SCREEN_HEIGHT = 800;
//forward delcarlation
//class Texture;
//start up SDL create window
bool init();
//load all media
bool load_media();
//free all and shut down SDL
void close();
//load global front
TTF_Font* g_font = NULL;
//window
SDL_Window* g_window = NULL;
//renderer
SDL_Renderer* g_renderer = NULL;
//load jpeg + font
//Texture background_texture;
//rendered font texture
Texture g_text_texture;
#endif
texture.h
//include guard
#ifndef TEXTURE_H
#define TEXTURE_H
//include dependencies
#include <SDL2/SDL.h>
#include <SDL2/SDL_image.h>
#include <SDL2/SDL_ttf.h>
#include <stdio.h>
#include <string>
//include headers
//#include "isolation.h"
class Texture {
public:
//initializes variables
Texture();
//deallocates memory
~Texture();
//load image from path
bool load_from_file( std::string path );
//create image from font string
bool load_from_rendered_text( std::string textureText, SDL_Color text_color );
//deallocates texture
void free();
//set color modulation
void set_color( Uint8 red, Uint8 green, Uint8 blue );
//set blend mode
void set_blend_mode( SDL_BlendMode blending );
//set alpha
void set_alpha( Uint8 alpha );
//render texture at point
void render( int x, int y, SDL_Rect* clip = NULL, double angle = 0.0, SDL_Point* center = NULL, SDL_RendererFlip flip = SDL_FLIP_NONE ) const;
//get image dimensions
int get_width() const;
int get_height() const;
private:
//texture pointer
SDL_Texture* m_texture;
//dimensions
int m_width;
int m_height;
};
#endif
init.cpp
#include "isolation.h"
//#include "texture.h"
bool init() {
//initialization flag
bool success = true;
//initialize SDL
if ( SDL_Init( SDL_INIT_VIDEO ) < 0 ) {
printf( "SDL could not initialized. SDL Error: %s\n", SDL_GetError() );
success = false;
}
else {
//set texture filtering linear
if ( !SDL_SetHint( SDL_HINT_RENDER_SCALE_QUALITY, "1" ) ) {
printf( "Warning: Linear filtering not enabled\n" );
}
//create window
g_window = SDL_CreateWindow( "Isolation", SDL_WINDOWPOS_UNDEFINED, SDL_WINDOWPOS_UNDEFINED, SCREEN_WIDTH, SCREEN_HEIGHT, SDL_WINDOW_SHOWN );
if ( g_window == NULL ) {
printf( "Window could not be created. SDL Error: %s\n", SDL_GetError() );
success = false;
}
else {
//create vsynced renderer
g_renderer = SDL_CreateRenderer( g_window, -1, SDL_RENDERER_ACCELERATED | SDL_RENDERER_PRESENTVSYNC );
if ( g_renderer == NULL ) {
printf( "Renderer could not be created. SDL Error: %s\n", SDL_GetError() );
success = false;
}
else {
//initialize renderer color
SDL_SetRenderDrawColor (g_renderer, 0xFF, 0xFF, 0xFF, 0xFF );
//initialize JPEG loading
int img_flags = IMG_INIT_JPG;
if ( !( IMG_Init( img_flags ) & img_flags ) ) {
printf( "SDL_image could not be initialize. SDL_image Error: %s\n", IMG_GetError() );
success = false;
}
//initialize SDL_ttf
if (TTF_Init() == -1 ) {
printf( "SDL_ttf could not be initialize. SDL_ttf Error: %s\n", TTF_GetError() );
}
}
}
}
return success;
}
load_media.cpp
#include "isolation.h"
//s#include "texture.h"
bool load_media() {
bool success = true;
//load background img
//if( !background_texture.load_from_file( "img/vancouver.jpg" ) ) {
// printf( "Failed to load background texture!\n" );
// success = false;
//}
//open font
g_font = TTF_OpenFont( "lazy.ttf", 28 );
if ( g_font == NULL ) {
printf( "Failed to load lazy font. SDL_ttf Error: %s\n", TTF_GetError() );
success = false;
}
else {
//render texture
SDL_Color text_color = { 0, 0, 0 };
if ( !g_text_texture.load_from_rendered_text( "hello from the other side ", text_color ) ) {
printf( "Failed to render text texture\n" );
success = false;
}
}
return success;
}
close.cpp
#include "isolation.h"
//#include "texture.h"
void close() {
//free loaded text
g_text_texture.free();
//free font
TTF_CloseFont( g_font );
g_font = NULL;
//destroy window
SDL_DestroyWindow( g_window );
SDL_DestroyRenderer( g_renderer );
g_window = NULL;
g_renderer = NULL;
//quit SDL subsystems
TTF_Quit();
IMG_Quit();
SDL_Quit();
}
main.cpp
#include "isolation.h"
//#include "texture.h"
int main( int argc, char* args[] ) {
//start up SDL
if ( !init() ) {
printf( "Failed to initialize.\n" );
}
else {
//load media
if ( !load_media() ) {
printf( "Failed to load media.\n" );
}
else{
//main loop flag
bool quit = false;
//event handler
SDL_Event e;
//while running
while ( !quit ) {
//handle events on queue
while ( SDL_PollEvent( &e ) != 0 ) {
//user quit
if ( e.type == SDL_QUIT ) {
quit = true;
}
}
//clear screen
SDL_SetRenderDrawColor( g_renderer, 0xFF, 0xFF, 0xFF, 0xFF );
SDL_RenderClear( g_renderer );
//render frame
g_text_texture.render( ( SCREEN_WIDTH - g_text_texture.get_width() ) / 2, ( SCREEN_HEIGHT - g_text_texture.get_height() ) / 2 );
//update screen
SDL_RenderPresent( g_renderer );
}
}
}
//free memory and close SDL
close();
return 0;
}

Answer 1

Do not mix declaration with definition/instantiation in a .h file. Your are instantiating g_font, g_window and g_renderer in isolation.h file. The correct is instantiating only once, usually, in a .cpp
To solve your problem, change isolation.h to declare those variables as external linkage:
//load global front
extern TTF_Font* g_font;
//window
extern SDL_Window* g_window;
//renderer
extern SDL_Renderer* g_renderer;
and instantiate them only once in an appropriate .cpp file, for example, init.cpp