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Masahiro Yamada 5e8c5299d3 kconfig: report recursive dependency involving 'imply'

Currently, Kconfig does not complain about the recursive dependency
where 'imply' keywords are involved.

[Test Code]

  config A
          bool "a"

  config B
          bool "b"
          imply A
          depends on A

In the code above, Kconfig cannot calculate the symbol values correctly
due to the circular dependency.  For example, allyesconfig followed by
syncconfig results in an odd behavior because CONFIG_B becomes visible
in syncconfig.

  $ make allyesconfig
  scripts/kconfig/conf  --allyesconfig Kconfig
  #
  # configuration written to .config
  #
  $ cat .config
  #
  # Automatically generated file; DO NOT EDIT.
  # Main menu
  #
  CONFIG_A=y
  $ make syncconfig
  scripts/kconfig/conf  --syncconfig Kconfig
  *
  * Restart config...
  *
  *
  * Main menu
  *
  a (A) [Y/n/?] y
    b (B) [N/y/?] (NEW)

To detect this correctly, sym_check_expr_deps() should recurse to
not only sym->rev_dep.expr but also sym->implied.expr .

At this moment, sym_check_print_recursive() cannot distinguish
'select' and 'imply' since it does not know the precise context
where the recursive dependency has been hit.  This will be solved
by the next commit.

In fact, even the document and the unit-test are confused.  Using
'imply' does not solve recursive dependency since 'imply' addresses
the unmet direct dependency, which 'select' could cause.

Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com>
Tested-by: Dirk Gouders <dirk@gouders.net>

2018-08-22 23:21:39 +09:00

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SPDX-License-Identifier: GPL-2.0

depends on itself

config A bool "A" depends on A

select itself

config B bool select B

depends on each other

config C1 bool "C1" depends on C2

config C2 bool "C2" depends on C1

depends on and select

config D1 bool "D1" depends on D2 select D2

config D2 bool

depends on and imply

config E1 bool "E1" depends on E2 imply E2

config E2 bool "E2"

property

config F1 bool "F1" default F2

config F2 bool "F2" depends on F1

menu "menu depending on its content" depends on G

config G bool "G"

endmenu

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