linux/Documentation/kbuild
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
..
00-INDEX Documentation: headers_install.txt is part of kbuild 2014-08-05 16:08:11 +02:00
headers_install.txt kbuild : Fix documentation of INSTALL_HDR_PATH 2015-06-22 09:56:07 -06:00
kbuild.txt kbuild: Use HOST*FLAGS options from the command line 2018-07-18 01:18:05 +09:00
kconfig-language.txt kconfig: report recursive dependency involving 'imply' 2018-08-22 23:21:39 +09:00
kconfig-macro-language.txt Documentation: kconfig: document a new Kconfig macro language 2018-05-29 03:31:19 +09:00
Kconfig.recursion-issue-01 kbuild: document recursive dependency limitation / resolution 2015-10-08 15:36:16 +02:00
Kconfig.recursion-issue-02 kbuild: document recursive dependency limitation / resolution 2015-10-08 15:36:16 +02:00
Kconfig.select-break kbuild: document recursive dependency limitation / resolution 2015-10-08 15:36:16 +02:00
kconfig.txt kconfig: update user kconfig tools doc. 2018-07-06 22:04:01 +09:00
makefiles.txt kbuild: if_changed: document single use per target limitation 2018-07-21 06:50:32 +09:00
modules.txt kbuild: Fix a typo in documentation 2014-06-10 14:14:29 +02:00