Author Topic: segfault while saving to png (Read 6931 times)

timesqueezer · « **on:** November 07, 2010, 02:51:20 am »

It seems that stbi_zlib_compress causes this segfault while saving an image as png. When I use jpg it works fine.

Here's the gdb trace:
Program received signal SIGSEGV, Segmentation fault.
0x00007ffff79601cf in stbi_zlib_compress(unsigned char*, int, int*, int) ()
from /usr/lib/libsfml2-graphics.so
(gdb) bt
#0 0x00007ffff79601cf in stbi_zlib_compress(unsigned char*, int, int*, int) ()
from /usr/lib/libsfml2-graphics.so
#1 0x00007ffff79612f9 in stbi_write_png_to_mem(unsigned char*, int, int, int, int, int*) ()
from /usr/lib/libsfml2-graphics.so
#2 0x00007ffff7961592 in stbi_write_png () from /usr/lib/libsfml2-graphics.so
#3 0x00007ffff7961c4b in sf::priv::ImageLoader::SaveImageToFile(std::basic_string<char, std::char_traits<char>, std::allocator<char> > const&, std::vector<unsigned char, std::allocator<unsigned char> > const&, unsigned int, unsigned int) () from /usr/lib/libsfml2-graphics.so

I'm working on a 64bit Arch Linux Laptop but it fails also on other systems.

Laurent · « **Reply #1 on:** November 07, 2010, 10:23:32 am »

Quote

it fails also on other systems

All 64 bits?

timesqueezer · « **Reply #2 on:** November 07, 2010, 01:55:02 pm »

Yes they're all 64bit.

Xorlium · « **Reply #3 on:** November 07, 2010, 04:56:31 pm »

I can confirm this. I had actually posted this some time ago:
http://www.sfml-dev.org/forum/viewtopic.php?t=3390

Xorlium

Svenstaro · « **Reply #4 on:** November 07, 2010, 05:13:52 pm »

Confirming as well. Arch Linux x86_64 here.

Laurent · « **Reply #5 on:** November 07, 2010, 05:43:16 pm »

I've sent an e-mail to the author of stb_image, hopefully he can do something about it.

Svenstaro · « **Reply #6 on:** November 07, 2010, 05:48:10 pm »

Laurent, can you replicate the problem at all?

Laurent · « **Reply #7 on:** November 07, 2010, 05:59:50 pm »

I haven't tried yet.

Anyway, here is his answer:

Quote

For the crashes, I don't know for sure, but try -fno-strict-aliasing

Svenstaro · « **Reply #8 on:** November 08, 2010, 07:27:25 pm »

Doesn't work here. I recompiled my whole project with that setting but no dice.

Laurent · « **Reply #9 on:** November 08, 2010, 08:08:09 pm »

I think SFML has to be recompiled with this option.

Svenstaro · « **Reply #10 on:** November 08, 2010, 08:27:00 pm »

That worked indeed. Stupid me, of course, recompiling my project with that option effectively didn't do anything. So, what are we going to do? Make -fno-strict-aliasing a compile option for SFML2 or should this still be delegated to the image library?

EDIT: From a few quick searches it appears as using that options is undesirable. The issue should be fixed in the image library.

Laurent · « **Reply #11 on:** November 08, 2010, 08:34:25 pm »

I agree. I'll see what the author can do.

Laurent · « **Reply #12 on:** November 08, 2010, 11:23:57 pm »

I can apply -fno-strict-aliasing to stb_image only, which is fair enough. The author made the choice to stop fixing code related to strict aliasing (I can show his answer to people who are interested).

I updated the makefiles, can everybody test it again please?

Xorlium · « **Reply #13 on:** November 09, 2010, 07:56:56 am »

Works well for me now.

Thanks Laurent!

Xorlium

Silvah · « **Reply #14 on:** November 09, 2010, 02:18:23 pm »

Quote from: "Laurent"

The author made the choice to stop fixing code related to strict aliasing (I can show his answer to people who are interested).

Sure, there's nothing wrong in depending upon undefined behavior, after all. I really wonder why he chose to leave the code broken.

Author Topic: segfault while saving to png (Read 6931 times)

Silvah