...
generalInterfaceTiledExamples.o(.text+0x36f): In function `writeTiled1(char const*, Imf::Array2D&, int, int, int, int)':
: undefined reference to `Imf::Channel::Channel(Imf::PixelType, int, int, bool)'
generalInterfaceTiledExamples.o(.text+0x3b3): more undefined references to `Imf::Channel::Channel(Imf::PixelType, int, int, bool)' follow
gmake[1]: *** [imfexamples] Error 1
gmake[1]: Leaving directory `/usr/work/usr/ports/graphics/OpenEXR/work/openexr-1.6.0/IlmImfExamples'
gmake: *** [all-recursive] Error 1
*** Error code 2

Remembering that in UPDATING there was something about this, I had another look:

20071008:
  AFFECTS: users of graphics/OpenEXR and graphics/ilmbase
  AUTHOR: nork@FreeBSD.org
...
  # pkg_delete -f OpenEXR
  # pkg_delete -f ilmbase       (if you already installed before CONFLICT)
  # cd /usr/ports/graphics/OpenEXR
  # make install
  # pkgdb -F

Nope, that didn’t help. pkg_delete told me ilmbase wasn’t installed. A quick Google turned up a PR about this, but it was closed with “look at UPDATING.” so that didn’t help any more.

I fixed it by rebuilding graphics/ilmbase anyway. Once that was rebuild and reinstalled, OpenEXR built fine. No idea why pkg_delete didn’t think it was installed.