Currently, C99 is required, but there are a couple of anonymous struct definitions that trigger warnings:

In file included from ../change.c:16:
../atom.h:47:10: warning: ISO C99 doesn’t support unnamed structs/unions [-Wpedantic]
   47 |         };
      |          ^
In file included from ../change.c:17:
../hunk.h:75:10: warning: ISO C99 doesn’t support unnamed structs/unions [-Wpedantic]
   75 |         };
      |          ^
../change.c: In function ‘print_atom’:

Changing to C11 would make this warning go away, but do we want to do that?

Fixed in WGYMYRCYRORAEVJKVEY34SBUDLI3VAERXKZ6QLV6MJWQR3G5SCXQC