Documentation/kbuild/Kconfig.select-break

   1 # Select broken dependency issue
   2 # ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
   3 #
   4 # Test with:
   5 #
   6 # make KBUILD_KCONFIG=Documentation/kbuild/Kconfig.select-break menuconfig
   7 #
   8 # kconfig will not complain and enable this layout for configuration. This is
   9 # currently a feature of kconfig, given select was designed to be heavy handed.
  10 # Kconfig currently does not check the list of symbols listed on a symbol's
  11 # "select" list, this is done on purpose to help load a set of known required
  12 # symbols. Because of this use of select should be used with caution. An
  13 # example of this issue is below.
  14 #
  15 # The option B and C are clearly contradicting with respect to A.
  16 # However, when A is set, C can be set as well because Kconfig does not
  17 # visit the dependencies of the select target (in this case B).  And since
  18 # Kconfig does not visit the dependencies, it breaks the dependencies of B
  19 # (!A).
  20
  21 mainmenu "Simple example to demo kconfig select broken dependency issue"
  22
  23 config A
  24         bool "CONFIG A"
  25
  26 config B
  27         bool "CONFIG B"
  28         depends on !A
  29
  30 config C
  31         bool "CONFIG C"
  32         depends on A
  33         select B