David Kastrup [off-list ref] writes:
... I am pretty sure I have seen size calculations in
the deltifying code that would break badly using FLEX_ARRAY=1. So _IFF_
-DFLEX_ARRAY=1 is supposed to be necessary for some compilers, I could
try seeing whether I find those locations again.
I do recall that I received a patch with an explicit member
elem[1] that is in fact used as a flexible array, foolishly
converted it to use FLEX_ARRAY and saw it mysteriously fail, and
realized what it was doing and reverted my changes, and applied
the patch as received. IIRC it all happened before I pushed the
results out. I unfortunately do not recall which area the patch
was about.