The fuzzer bug reported https://github.com/libvips/libvips/actions/runs/17152025286/job/48660246466 is quite interesting. It seems that the removal of the seq hint in reducev means we can no longer guarantee buffer alignment, which was previously ensured here:

At first, I thought this would be an easy fix (see commit baf91e4), but it turned out to confuse FFTW's SIMD alignment checks, which I worked around in commit f570895.

Unfortunately, crashes still occur in certain cases, for example:

$ vips black crash1.pgm 1 70
$ ./build/fuzz/thumbnail_fuzzer -rss_limit_mb=2560 -timeout=25 -runs=100 ./crash1.pgm < /dev/null

i.e. we can't guarantee that image->data is properly aligned, since it can also be initialized via vips_image_new_from_memory().

I dropped the previous mentioned commits in favor of commit 3037cb3, but still need to verify whether that is safe on all targets.