Float And Sdl Problems

[charlieb]

Hi,
I'm trying to compile the and simple SDL demo with open2x. I had some problems to start with but now it works when I compile it like this:

open2x-gcc -c -Wall -I/usr/local/open2x/include -I/usr/local/open2x/include/SDL -D_REENTRANT demo.c -o demo.o
open2x-gcc demo.o -o helloworld.gpe -msoft-float-L/usr/local/open2x/lib -Wl,-rpath,/usr/local/open2x/lib -lSDL -lpthread -lm -ldl

I actually use `/usr/local/open2x/bin/sdl-config --cflags` and `/usr/local/open2x/bin/sdl-config --static-libs` for compiling but I thought the expanded version would be more instructive.

If I add a float to the source then at runtime I get the following:
./helloworld.gpe: relocation error: ./helloworld.gpe: undefined symbol: __extendsfdf2

If I compile it with the static flag I don't get the have any problem with floats but instead of the image the program is supposed to display I get some unpleasant black and white bands on the screen. The app responds to events as expected and when I quit the app I see a flash of the image it should be displaying just before it exits to the menu.
Any ideas how to solve or investigate this?

Cheers,
Charlie

 

[poddy]

hi charlie,
been scratching around and got this far with it...
i'm initialising with
screen = SDL_SetVideoMode(GP2X_WIDTH,
GP2X_HEIGHT,
16,
SDL_DOUBLEBUF | SDL_HWSURFACE
);

SDL_PixelFormat *pf = NULL;
pf = screen->format;
black = SDL_MapRGB(pf, 0x00, 0x00, 0x00);

and then v. last thing in the game loop is
SDL_Flip(screen);
SDL_FillRect(screen, NULL, black);

although sdl docs suggest that its flip for hw and fill for soft, but both seem to be needed.
i'm also still getting a mangled screen if i use any kind of optimisation (-O3 etc),
only -O0 is good.
this is using static linkage, open2x and hw sdl.

hope it helps some.

edited for explaining where 'black' came from

 

[charlieb]

Poddy,
I actually managed to get half way to solving this. It seems to all depend on the order of the arguments. The compile command that worked for me was
open2x-gcc main.o matrix.o figures.o fixed.o -o bin/wire3d.gpe -lSDL_gfx -msoft-float -lm -lg -lpthread -static `/usr/local/open2x/bin/sdl-config --static-libs`
note that the object files (.o) are before all the library references. Normally I like to put the .o at the end. I recall the position of the -static matters as well but in any case that works for SDL *but* I still can't use floats, despite the -msoft-float. I hadn't tried any optimization settings so that's interesing (-O2 is the defaule IIRC).

SDL_Flip just swaps the buffers, it doesn't clear them. If you aren't going to re-draw the entire frame you do indeed need to do an SDL_FillRect(surface, NULL, colour).

Are you using any floats in your program?

Cheers,
Charlie

P.S. Have a look at this thread, it covers most of the same ground.

 

[poddy]

hi charlie,
seems we're all getting subtly different results?

lobbed a float in, didn't do anything with it, just initialised it, but should still count i guess?

compiled and ran fine.

i'm using this as a makefile if its any use

# Global definitions

CCPREFIX  = open2x-
CC		= ${CCPREFIX}gcc
STRIP	 = ${CCPREFIX}strip
AS		= ${CCPREFIX}as

PREFIX	= /usr/local/open2x
OBJS	  = mat.o
BIN	   = mat.gpe 

# Platform specific definitions 

VPATH	  += ..
CFLAGS	 += -O0 -DGP2X_BUILD
CFLAGS	 += -funroll-loops -fstrength-reduce -fstrict-aliasing -fexpensive-optimizations -falign-functions -fweb -frename-registers -fomit-frame-pointer -ffast-math -fno-builtin -fno-common -finline -finline-functions
CXXFLAGS   = ${CFLAGS} -fno-exceptions -fno-rtti
ASFLAGS	   = ${CFLAGS}
INCLUDES   = -I${PREFIX}/include -I${PREFIX}/include/SDL
LIBS	   = -L${PREFIX}/lib -lSDL -lpthread -lz -lm -static

# Compilation:

.SUFFIXES: .cpp

%.o: %.cpp
	${CC} ${CFLAGS} ${INCLUDES} -c -o $@ $<

all:	${OBJS}
	${CC} ${OBJS} ${LIBS} -o ${BIN}  
	${STRIP} ${BIN}

clean:
	rm -f *.o ${BIN} 

linux:
	make clean
	make -f ./makefile.linux

edited because i read the other thread

codeblocks looks interesting, might give that a go.
weird about the sdl flip, though.
from tfm...
On hardware that doesn't support double-buffering, this is equivalent to calling SDL_UpdateRect (screen, 0, 0, 0, 0)
way i read it was that this implies you can just do a flip with SDL_DOUBLEBUF | SDL_HWSURFACE

live & learn

 

[charlieb]

On hardware that doesn't support double-buffering, this is equivalent to calling SDL_UpdateRect (screen, 0, 0, 0, 0)
way i read it was that this implies you can just do a flip with SDL_DOUBLEBUF | SDL_HWSURFACE

Your makefile worked! I'm happy. I also moved the -staic flag in my makefile to where it is in yours and it still worked. I didn't need to turn off optimization. This whole arguement order thing is messing with my mind but at least it works now. Here's my makefile for reference:

GP2XDEV=/usr/local/open2x
PATH+=:$(GP2XDEV)/bin

CFLAGS=-c -Wall
LDFLAGS=-lm -lg -lpthread -lSDL
GPLDFLAGS=`$(GP2XDEV)/bin/sdl-config --static-libs` -static
SOURCES=boids.c sdl-main.c
OBJECTS=$(SOURCES:.c=.o)
EXECUTABLEPC=boids
EXECUTABLEGP=boids.gpe
DEST=bin

ifdef arm
CC=open2x-gcc
CFLAGS+=-msoft-float -D_GP2X_ -I$(GP2XDEV)/include `$(GP2XDEV)/bin/sdl-config --cflags`
else
CC=gcc
CFLAGS+=-D_PC_ -I/usr/include/SDL
endif

all:
	make cleanobjs
	make pc
	make cleanobjs
	make arm=1 gp
	make cleanobjs

pc: $(SOURCES) $(EXECUTABLEPC)

gp: $(SOURCES) $(EXECUTABLEGP)

$(EXECUTABLEPC): $(OBJECTS) 
	$(CC) $(LDFLAGS) $(OBJECTS) -o $(DEST)/$@

$(EXECUTABLEGP): $(OBJECTS) 
	$(CC) $(OBJECTS) -o $(DEST)/$@ $(GPLDFLAGS) $(LDFLAGS) 

.c.o:
	$(CC) $(CFLAGS) $< -o $@

cleanobjs:
	rm -f $(OBJECTS)

clean:
	-rm -f $(DEST)boids $(DEST)/boids.gpe *~ *.o


fixed:
	gcc -Wall -o $(DEST)/fixed fixed.c

On hardware that doesn't support double-buffering, this is equivalent to calling SDL_UpdateRect (screen, 0, 0, 0, 0)
way i read it was that this implies you can just do a flip with SDL_DOUBLEBUF | SDL_HWSURFACE

You can just do SDL_Flip with either if all you want to do is update the whole screen. AFAIK neither of these commands changes the conent of the surface they just updates the screen; in either case if you want to clear the screen before you redraw the frame you need to do a drawing operation like SDL_FillRect.

Cheers,
Charlie