The following command line:

  bin/gs -sDEVICE=pxlcolor -o test.pxl ./tests_private/comparefiles/Bug687044.ps

produces an error when run with the device_subclassing branch build:

GPL Ghostscript GIT PRERELEASE 9.18 (2015-04-07)
Copyright (C) 2015 Artifex Software, Inc.  All rights reserved.
This software comes with NO WARRANTY: see the file PUBLIC for details.
Loading StandardSymL font from %rom%Resource/Font/StandardSymL... 4265572 2862621 5438200 4048759 1 done.
Error: /undefinedresult in --.FAPIBuildChar--
Operand stack:
   false   (\307)   --dict:14/14(ro)(L)--   199
Execution stack:
   %interp_exit   .runexec2   --nostringval--   --nostringval--   --nostringval--   2   %stopped_push   --nostringval--   --nostringval--   --nostringval--   false   1   %stopped_push   1951   1   3   %oparray_pop   1950   1   3   %oparray_pop   1934   1   3   %oparray_pop   1820   1   3   %oparray_pop   --nostringval--   %errorexec_pop   .runexec2   --nostringval--   --nostringval--   --nostringval--   2   %stopped_push   --nostringval--   %finish_show   --nostringval--   --nostringval--   6   5   0   --nostringval--   (gs_show_enum)   %op_show_continue   --nostringval--   --nostringval--   %finish_show   --nostringval--   --nostringval--   8   7   2   --nostringval--   (gs_show_enum)   %op_show_continue
Dictionary stack:
   --dict:1183/1684(ro)(G)--   --dict:4/20(G)--   --dict:86/200(L)--   --dict:156/227(L)--   --dict:293/400(L)--   --dict:20/28(ro)(L)--   --dict:2/5(L)--
Current allocation mode is local
Last OS error: No such file or directory
Current file position is 740231
GPL Ghostscript GIT PRERELEASE 9.18: Unrecoverable error, exit code 1



Note this effects the following input files:

  tests_private/comparefiles/Bug687044.ps
  tests_private/comparefiles/Bug688796a.eps
  tests_private/comparefiles/Bug690164.ps
  tests_private/comparefiles/Bug691734.ps
  tests_private/comparefiles/Bug692120.ps
  tests_private/comparefiles/Bug692240.ps
  tests_private/comparefiles/Bug692517.pdf
  tests_private/comparefiles/Bug694871.eps
  tests_private/ps/ps3cet/18-01A.PS
  tests_private/ps/ps3cet/27-06.PS
  tests_private/ps/ps3cet/27-07.PS