Misaligned address SIGBUS in CGImageSourceCreateImageAtIndex

[lczyk]

See this issue. I believe this is potentially a SDL_image bug??

Briefly;

• working on mac M3, Sequoia 15.1.1.
• trying to load a texture with texture = IMG_LoadTexture(renderer, "spritesheet.png");
• getting a Job 1 terminated by signal SIGBUS (Misaligned address error)
• traced it down to SDL_image/src/IMG_ImageIO.m to CreateCGImageFromCGImageSource to image_ref = CGImageSourceCreateImageAtIndex(image_source, 0, NULL); (docs)
• changing 0 to -1 makes it work
• printf("image_count: %lu\n", CGImageSourceGetCount(image_source)); prints 1

[lczyk]

Working with the current head branch of SDL_image 33d18dd.

[slouken]

That's really interesting. The documentation for CGImageSourceCreateImageAtIndex() says:

index
The zero-based index of the image you want. If the index is invalid, this method returns NULL.

It seems like -1 is an invalid index and the function would return NULL. Is that what happens?

[lczyk]

Nope. I get an id of the ref to first image (which in this case is the spiresheet) and the game runs fine. Apple bug?? 🤨

[slouken]

I'm not sure how that's possible... is there a bug in ImageIO where it's using -1 based indices?

[lczyk]

Just checked and it also works with image_ref = CGImageSourceCreateImageAtIndex(image_source, 99, NULL), as well as 1, -10, 42 and pretty much any garbage i come up with except for 0.

[lczyk]

The steps to reproduce for me are literally to follow the build instructions of this repo.

[lczyk]

Ok, i have some progress. I don't think it's SDL_image actually. So, this is very weird but, my default terminal is fish and there it does not work with 0, but it works no problem when i do bash -c ./build/Debug/flappybird aka when I run it though bash. Also works for zsh. Running fish 3.7.1. I checked that its nothing to do with my config.fish.

[lczyk]

Just tried writing an issue on fish-shell GitHub and they suggest running with sh -c 'env HOME=$(mktemp -d) XDG_CONFIG_HOME= XDG_DATA_DIRS= fish' which does fix the problem. I've narrowed it down to sh -c 'env HOME=$(mktemp -d) fish' which makes it work (also checked XDG_CONFIG_HOME and XDG_DATA_DIRS are the same between fish and bash and zsh.

Looks like something to do with my $HOME, but unsure what yet.

[lczyk]

Also managed to get a bit of crash report from Apple by launching through a different terminal. Here is the relevant bit:

Crashed Thread:        0  Dispatch queue: com.apple.main-thread

Exception Type:        EXC_BAD_ACCESS (SIGBUS)
Exception Codes:       UNKNOWN_0x101 at 0x000000000bad4007
Exception Codes:       0x0000000000000101, 0x000000000bad4007

Termination Reason:    Namespace SIGNAL, Code 10 Bus error: 10
Terminating Process:   exc handler [61103]

VM Region Info: 0xbad4007 is not in any region.  Bytes before following region: 4111826937
      REGION TYPE                    START - END         [ VSIZE] PRT/MAX SHRMOD  REGION DETAIL
      UNUSED SPACE AT START
--->  
      __TEXT                      100c2c000-100c34000    [   32K] r-x/r-x SM=COW  /Users/USER/*/flappybird

Thread 0 Crashed::  Dispatch queue: com.apple.main-thread
0   ???                           	         0xbad4007 ???
1   ImageIO                       	       0x1abbf6d60 IIOReadPlugin::callInitialize() + 388
2   ImageIO                       	       0x1abbf6b08 IIO_Reader::initImageAtOffset(CGImagePlugin*, unsigned long, unsigned long, unsigned long) + 164
3   ImageIO                       	       0x1abbf41a0 IIOImageSource::makeImagePlus(unsigned long, IIODictionary*) + 832
4   ImageIO                       	       0x1abc6d620 IIOImageSource::createImageAtIndex(unsigned long, IIODictionary*, int*) + 112
5   ImageIO                       	       0x1abc0109c CGImageSourceCreateImageAtIndex + 464
6   libSDL2_image-2.0d.0.900.0.dylib	       0x100ce4848 CreateCGImageFromCGImageSource + 152 (IMG_ImageIO.m:160)
7   libSDL2_image-2.0d.0.900.0.dylib	       0x100ce45c4 LoadImageFromFile + 80 (IMG_ImageIO.m:508)
8   libSDL2_image-2.0d.0.900.0.dylib	       0x100ce44f4 IMG_Load + 168 (IMG_ImageIO.m:587)
9   libSDL2_image-2.0d.0.900.0.dylib	       0x100ca77dc IMG_LoadTexture + 32 (IMG.c:307)
10  flappybird                    	       0x100c334f8 main + 772 (flappybird.c:1122)
11  dyld                          	       0x1a00bc274 start + 2840                          	       0x1a00bc274 start + 2840