Cross compilation with SDL

Please try the cross compiling instructions.


Cross compiling under Linux using mingw. At the link stage, I get a lot of
undefined reference for call to lib function, e.g. SDL. Looks like the linker
thinks the routine name should start with _ , e.g _IMG_Load instead of IMG_Load.

I know this must be a classical problem, but I have no clue of what option to
use in gcc (mingw)


I just simply forgot to put the LD flags after the list of objects in my makefile

# barebones whitenoise Makefile for MINGW
# edit to fit your needs

CC = i586-mingw32msvc-gcc
SDLROOT = ../libsdl-mingw
CFLAGS = `$(SDLROOT)/bin/i586-mingw32msvc-sdl-config --cflags` -DWIN32_PLATFORM
LDFLAGS = -static
LIBS = -mconsole -lm `$(SDLROOT)/bin/i586-mingw32msvc-sdl-config --static-libs`

# main targets
all: wnoise.exe

OBJECTS = filter.o plot.o whitenoise.o

wnoise.exe: $(OBJECTS)
	$(CC) -o wnoise.exe $(LDFLAGS) $(OBJECTS) $(LIBS)

clean:
	rm -f wnoise.exe *.o core *~

distclean: clean
	rm -f Makefile configure config.h config.log config.status; 
	rm -rf autom4te.cache

# suffixes
.c.o: 
	$(CC) -c $(CFLAGS) $<


>usr/lib/gcc/i586-mingw32msvc/3.4.2/../../../../i586-mingw32msvc/lib/libmingw32.a(main.o)(.text+0xf4):
>> undefined reference to `_WinMain@16'
>> collect2: ld returned 1 exit status

Remember to link with SDLmain? When I'm compiling with Mingw, at least the following linker flags should be used (they should be given by i586-mingw32msvc-sdl-config) : -lmingw32 -lSDLmain -lSDL



If you are cross-compiling from the same folder you have the linux build in (where the .o files are) then do not forget to 'make clean' before you build for win32. Same thing before you do 'sh cross-make.sh -f Makefile.win32'. One can make a separate makefile for the win32 build to make things easier - one can even rename .o files to .o32 for win32 compiling for safety.



Your entry point is main(), right? I use something like this :

#ifdef WIN32
extern "C"
{

int __stdcall WinMain(HINSTANCE hInstance, HINSTANCE hPrevInstance,
char* lpCmdLine, int nCmdShow)
{

	// Parse command line
	String sParms = lpCmdLine;
	StringList lParms = sParms.split();

	int nParms = lParms.getLength();
	char** pParms = new (char*)[nParms + 1];

	pParms[0] = new char[8];
	strcpy(pParms[0], "(dummy)");

	for (int i = 0; i < nParms; i++)
	{
		pParms[i+1] = new char[strlen(lParms[i]) + 1];
		strcpy(pParms[i+1], lParms[i]);
	}

	// Do main
	int nRet = main(nParms + 1, pParms);

	// Cleanup
	for (int i = 0; i < nParms + 1; i++)
		delete pParms[i];

	delete [] pParms;

	return nRet;
}

}
#endif











If you are cross-compiling to Win32 from Linux on a PC, get tools from:
http://www.devolution.com/~slouken/SDL/Xmingw32/
and pass configure the arguments "--host=i386-linux --target=i386-mingw32"


http://www.libsdl.org/faq.php?action=listentries&category=4#47 
http://gameprogrammer.com/gpwiki/The_20basics_20of_20working_20with_20SDL


I've updated the Windows cross-compiling tools to the latest version
of gcc and mingw32.  You can get them here:
http://www.libsdl.org/extras/win32/cross/README.txt
http://www.libsdl.org/extras/win32/cross/mingw32-linux-x86-glibc-2.3.tar.gz

$ sh cross-make.sh 
   gcc -o 01-window  init.o  main.o  video.o  yerror.o `sdl-config --libs`
   -lGL -lGLU -lm
   /usr/local/cross-tools/lib/gcc-lib/i386-mingw32msvc/3.2.3/../../../../i386-mingw32msvc/bin/ld:
   cannot find -lpthread
   make: *** [01-window] Error 1



Which "sdl-config" are you running?  (i.e., what's its path?)
If it's the Linux one, that could be causing probs (similarly to trying
to link the Win32 against Linux libs :^) )

I'm guessing it should be the one from that "SDL-devel-1.2.7-mingw32.tar.gz"
you had downloaded.


To be even more specific : replace `sdl-config --libs` with 
`/usr/local/cross-tools/i386-mingw32msvc/bin/sdl-config --libs`

Although I'm using SDL_mixer I think it's a problem related to SDL + 
MinGW because if I copy in the precompiled sdl.dll from libsdl.org 
(which as far as I know is not compiled using mingw) the problem 
disappears! However those procompiled dlls don't really help me because 
the precompiled smpeg.dll seems to have problems with the precompiled 




sdl.dll (black screen on videos).


THe MingW version may be using WaveOut, where the VC version may be
using DirectSound.  SDL's WaveOut implementation enforces 250ms buffering.
I've found that at 44.1khz, an 8k frame buffer is needed, which is
about 185ms.  DirectSound doesn't need as much--2k usually works fine.
WaveOut should only ever be used as a compatibility, fallback interface.


Never realized that there was a check for directx headers when compiling 
SDL. After a couple of hours I figured out that I had to use the headers 
from http://www.libsdl.org/extras/win32/common/directx-devel.tar.gz, 
recompiled SDL with directX support and now the sound is playing nicely.

I'm however running into a different problem now. In fact, it's the same 
problem I get when using the precompiled dlls: smpeg doesn't display 
anything anymore. Neiter the code in my app nor the plaympeg example 
supplied with smpeg have a graphical output anymore, just a black screen.


If you only use standard C (C++) libraries, you should be OK when 
porting. But if one doesn't have enough experience in programming for 
various platforms, you're gonna one way or the other use some 
non-standard features of your compiler and/or OS. This may be just a 
glitch or a major obstacle when porting.
Another problem may be performance. Not always but sometimes different 
platform perform different jobs at (drastically) different speeds. So 
when writing code, you'll have to take these into consideration, and 
either write two versions of code, or use an 
always-performing-reasonable approach.