Question

I’m using SDL with FASM, and have code that’s minimally like the following:

format ELF

extrn _SDL_Init
extrn _SDL_SetVideoMode
extrn _SDL_Quit
extrn _exit
SDL_INIT_VIDEO equ 0x00000020

section '.text'
public _SDL_main
_SDL_main:

    ccall   _SDL_Init, SDL_INIT_VIDEO
    ccall   _SDL_SetVideoMode, 640, 480, 32, 0
    ccall   _SDL_Quit
    ccall   _exit, 0 ; Success, or
    ret              ; failure.

With the following quick-and-dirty makefile:

SOURCES = main.asm
OBJECTS = main.o
TARGET = SDLASM.exe
FASM = C:\fasm\fasm.exe

release : $(OBJECTS)
    ld $(OBJECTS) -LC:/SDL/lib/ -lSDLmain -lSDL -LC:/MinGW/lib/ -lmingw32 -lcrtdll -o $(TARGET) --subsystem windows

cleanrelease :
    del $(OBJECTS)

%.o : %.asm
    $(FASM) $< $@

Using exit() (or Windows’ ExitProcess()) seems to be the only way to get this program to exit cleanly, even though I feel like I should be able to use retn/retf. When I just ret without calling exit(), the application does not terminate and needs to be killed. Could anyone shed some light on this? It only happens when I make the call to SDL_SetVideoMode().

Answer 1

I noticed that ret works to end the program, but as far as I know that’s not guaranteed anywhere by Microsoft.
The official way to end a program is to call exit() or ExitProcess().

(In C, the compiler has to arrange the code so that it is equivalent to calling exit().
Also, I suspect that a lot of existing programs use ret instead, of it seems unlikely that Microsoft would change that behavior.)

About your problem, SDL does some black magic before your program is called: http://www.libsdl.org/faq.php?action=listentries&category=4#48.
I would suggest that you use a main() entry point, as suggested in the FAQ.