title: What does "linker input file unused because linking not done" mean? (C makefile)
body: <p>I have created a makefile to compile and link my program, however, I can't figure out why I am getting this error. Is it to do with SDL?</p>
  
  <pre><code>GCC = gcc
  CFLAGS = -c -std=c99 -lm -Wall -Wextra -pedantic -O3 -Wfloat-equal -g
  SDL = -lSDL2 -lSDL2_ttf -lSDL2_image -lSDL2_mixer
  
  all: ./game
  
  game: global.o display.o player.o entities.o controls.o sound.o menu.o
      $(GCC) $(CFLAGS) global.o display.o player.o entities.o controls.o sound.o menu.o -o game
  
  global.o: global.c
      $(GCC) $(CFLAGS) $(SDL) global.c
  
  display.o: display.c
      $(GCC) $(CFLAGS) $(SDL) display.c
  
  player.o: player.c
      $(GCC) $(CFLAGS) $(SDL) player.c
  
  entities.o: entities.c
      $(GCC) $(CFLAGS) $(SDL) entities.c
  
  controls.o: controls.c
      $(GCC) $(CFLAGS) $(SDL) controls.c
  
  sound.o: sound.c
      $(GCC) $(CFLAGS) $(SDL) sound.c
  
  menu.o: menu.c
      $(GCC) $(CFLAGS) $(SDL) menu.c
  
  clean:
      rm *o game
  </code></pre>