Control: forwarded -1 https://gitlab.gnome.org/GNOME/gtk/-/issues/7801 Control: tags -1 +patch
Hi Gregor, On Sat, 2025-10-25 at 13:50 +0200, Gregor Riepl wrote: > The gtk4 package build currently fails on architectures with strict memory > alignment rules, namely sparc64. > > The errors manifest as bus errors due to unaligned memory access in unit > tests for mipmap conversion routines. [1] > > These unit test use the helper function texture_builder_init[2], which > unconditionally calls gdk_memory_layout_init[3] > and gdk_memory_layout_fudge[4] with a required memory alignment of 1 byte. > gdk_memory_layout_fudge[4] will then generate a randomized memory layout for > storing pixel data. > This function would actually honor a requested memory alignment, but not if > the alignment is always 1. > With a requested alignment of 1, it may generate data offsets that cause > errors when accessing 16- or 32-bit pixel > formats, which must be aligned at 2 or 4 byte boundaries on sparc64. > > I can see several possible fixes for this issue: > > 1. Always enforce the minimum required alignment based on the underlying data > types. This is the most drastic > change and will require modifying gdk_memory_layout_init.[2] > 2. Enforce the minimum required alignment only on CPU architectures that > require it. This would fix the issue, > but may also cause problems when a specific memory layout is expected by an > application. > 3. Fix the unit test by always requesting a memory layout with adequate > alignment in texture_builder_init.[2] > > Option 3. seems to be the most prudent, since it wouldn't cause problems on > other architectures where the memory > alignment doesn't matter. On the other hand, it would hide the fact that > inadequate memory alignments in user > programs may lead to crashes when the target CPU doesn't support it. > > I've included an untested patch for option 3. Thanks a lot for the detailed analysis and trial patch. I have already created an upstream issue [1] for this bug some weeks ago but my proposed patch isn't really working and just a really poor shot in the dark. I am adding the URL to the upstream bug report and will also give your patch a try on the Debian sparc64 porterbox. Adrian > [1] https://gitlab.gnome.org/GNOME/gtk/-/issues/7801 -- .''`. John Paul Adrian Glaubitz : :' : Debian Developer `. `' Physicist `- GPG: 62FF 8A75 84E0 2956 9546 0006 7426 3B37 F5B5 F913
