Question

This is my makefile:

CFLAGS = -Wall -pedantic -pedantic-errors -g -lSDL -lSDL_image
CC = g++
OBJ = Point.o Personaje.o Juego.o EventHandler.o

all: main

#%.o: %.cpp %.h
#   $(CC) -c $(CFLAGS) $<

bin: other $(OBJ)

Point.o: Point.cpp Point.h
    $(CC) -c $(CFLAGS) $<

Personaje.o: Personaje.cpp Personaje.h
    $(CC) -c $(CFLAGS) $<

Juego.o: Juego.cpp Juego.h
    $(CC) -c $(CFLAGS) $<

EventHandler.o: EventHandler.cpp EventHandler.h
    $(CC) -c $(CFLAGS) $<

main: $(OBJ)
    cd ../vista/; make
    cp ../vista/*.o .
    rm ../vista/*.o
    g++ $(CFLAGS) $(OBJ) Pantalla.o Imagen.o main.cpp -o main

clean:
    rm *.o;
    rm main

PHONY: main

When I compile with “make” I get the following errors:

EventHandler.cpp:17: undefined reference to `SDL_PollEvent'
Pantalla.o: In function `Pantalla::initialize(int, int, int, std::basic_string<char, std::char_traits<char>, std::allocator<char> >)':
Pantalla.cpp:6: undefined reference to `SDL_Init'
Pantalla.cpp:9: undefined reference to `SDL_SetVideoMode'
Pantalla.cpp:14: undefined reference to `SDL_WM_SetCaption'

and many other errors.

The header of “Pantalla.h” contains this line:

#include "SDL/SDL.h"

And I already installed the SDL packages.

I don’t know what I’m doing wrong… please help!

Answer 1

CFLAGS = -Wall -pedantic -pedantic-errors -g -lSDL -lSDL_image

This isn’t good. You’re mixing compiler flags (warnings and debug) with linker information (which libraries you need to link to). Use two separate variables for that:

CFLAGS = -Wall -pedantic -pedantic-errors -g
LIBS = -lSDL -lSDL_image

Then when you compile (but don’t link, i.e. when you generate the .o files), only use $(CFLAGS) (like you have now). But when you do link (to produce the final executable), add the linker directives.

g++ $(CFLAGS) -o main main.cpp $(OBJ) Pantalla.o Imagen.o $(LIBS)

The order you put your objects and libraries is important.