Re: Patch for graphics/lcms2 (alignment issues on sparc)

[David Holland <dholland-pkgtech%netbsd.org@localhost>]

On Sat, Oct 31, 2026 at 09:05:04PM -0400, Greg Troxel wrote:
 > > Maybe this should be alignof(max_align_t) instead?  I expect this
 > > affects more than just sparc32.
 > 
 > In this case, we really need to know the alignment for doubles, as I
 > understand it.  Having some other type with even biggger alignment would
 > cause max_align_t to be bigger, and that would be wasteful.
 > 
 > Anyone with a retro arch that needs more then 4 for doubles, please
 > speak up.

You can do something like

   union foo {
           int y;
           double x;
           char *z;
   };

that specifically includes exactly the types needed, and ask for its
alignment.

In the absence of alignof, it's probably sufficient to also do

   struct bar {
           unsigned char a;
           union foo b;
   };

and take offsetof(struct bar, b). There's no guarantee that compilers
won't insert extra padding in structs, but reasonable ones don't.

-- 
David A. Holland
dholland%netbsd.org@localhost