Difference between revisions of "Developer tips"

From WiiBrew
Jump to navigation Jump to search
(Must be misspelled. 480p doesn't exist on RGB cables but only on component cables, plus PAL60=480i.)
m (addendum to "Exit to Loader" (return doesn't work))
Line 44: Line 44:
 
     // ....
 
     // ....
 
     exit(0);
 
     exit(0);
 +
 +
PS: maybe it's just me, but "return" never works. "exit(0)" does fine. [[aksommerville]]
  
 
=Debugging Tip=
 
=Debugging Tip=

Revision as of 21:43, 23 May 2008

Code Snippets

Video Auto-Detect Routine

Please include an autodetect routine (VIDEO_GetCurrentTVMode()) to detect HDTV/EDTV and set the appropriate video mode.

The current video autodetect routine doesn't work with PAL60 (480i @ 60 Hz in PAL Wii) using the offical Nintendo RGB cable for Wii.

Here is the video detect code from the DevKitPro Wii example.

   switch(VIDEO_GetCurrentTvMode())
   {
       case VI_NTSC:
           rmode = &TVNtsc480IntDf;
       break;
       case VI_PAL:
           rmode = &TVPal528IntDf;
       break;
       case VI_MPAL:
           rmode = &TVMpal480IntDf;
       break;
       default:
           rmode = &TVNtsc480IntDf;
       break;
   }
   VIDEO_Configure(rmode);

Reboot Wii

It's a good idea to include a way to reboot the Wii in all Homebrew. Here's the source code to do it.

void Reboot()
{
	// Thanks to hell_hibou
	int fd = IOS_Open("/dev/stm/immediate", 0);
	IOS_Ioctl(fd, 0x2001, NULL, 0, NULL, 0);
	IOS_Close(fd);
}

Exit to Loader

It's a good idea to add some way to return to the loader, otherwise you have to reboot you Wii to exit.

   // Just include the unistd.h header and call the exit() function to go back to the loader
   // Returning from main also works, since that calls exit for you
   #include <unistd.h>
   // ....
   exit(0);

PS: maybe it's just me, but "return" never works. "exit(0)" does fine. aksommerville

Debugging Tip

When faced with a crash in your Homebrew, often you'll see a code dump with an address and some machine code. Here's my trick to track that back to a line of C++ code.

For example if your homebrew game crashes it might show something like this:

    CODE DUMP:
    
    800084ac:   809F0020 2F840000 ...
    800084bc:   ...
    800084cc:   ...

The 800084ac is the memory address in hex of where the crash occured. 809F0020 is the machine code for the offending instruction.

  • Step 1:

In your makefile change the CXXFLAGS line to the following:

  CXXFLAGS = -save-temps -Xassembler -aln=$@.lst $(CFLAGS)

The "-save-temps" will save the assembly language file, which can be interesting. The "-Xassembler -aln=$@.lst" creates a list file which contains the assembly and the machine code. Now recompile your entire project. Note, this just affects C++ code.

  • Step 2:

Look at the map file that was built. The mapfile is on by default in the Wii template makefile. Typically it's in the build subdirectory and called something.map. Look in that mapfile for the nearest memory address that doesn't go over the one found in the CODE DUMP. Here is an example:

    0x80008464                ShooterView::Render(BibGraphicsDevice&)

This tells me that the crash was 72 bytes into the ShooterView::Render() function. Now to find the line number in Render()

  • Step 3:

Look at the list file for the relevant function. Here's an example:

   473              		.globl _ZN11ShooterView6RenderER17BibGraphicsDevice
   474              		.type	_ZN11ShooterView6RenderER17BibGraphicsDevice, @function
   475              	_ZN11ShooterView6RenderER17BibGraphicsDevice:
   476              	.LFB1465:
   477              		.loc 1 158 0
   478              	.LVL20:
   479 02d0 9421FF00 		stwu 1,-256(1)

The function names are mangled because this is C++ code. See http://en.wikipedia.org/wiki/Name_mangling#Name_mangling_in_C.2B.2B The address of the first instruction of Render() is at 02d0. This is also line 158 in the file (".loc 1 158 0"). To find the error location, just look at 0x2d0 + 72 = 0x318. See below:

                               .loc 1 168 0
   528 0314 809F0020 		lwz 4,32(31)
   529 0318 2F840000 		cmpwi 7,4,0

This shows machine address 0x318 has the proper machine code and the nearest .loc statement says the problem is at line 168 of the ShooterView.cpp. For more info on the assember output see the manual here: http://sourceware.org/binutils/docs-2.18/as/index.html