When reading .config input, Kconfig stores user-provided values first
and then resolves the final value after applying dependencies, ranges,
and other constraints.

If the final value differs from the user input, Kconfig already tracks
that state internally, but it does not provide a focused diagnostic to
show which explicit inputs were adjusted. This is particularly confusing
for requested values that get forced down by unmet dependencies or
clamped by ranges.

Add an opt-in diagnostic controlled by KCONFIG_WARN_CHANGED_INPUT. Emit
the warnings from conf_write() and conf_write_defconfig() after value
resolution. Print the diagnostic to stderr directly, not through the
normal message callback, so it remains visible when conf is run with -s,
such as from make -s.

Keep the diagnostic out of the conf_message() formatting buffer so long
warning lists are not truncated, and mark processed symbols as written
before the SYMBOL_WRITE check so duplicate menu nodes cannot emit
duplicate warnings.

Document the new environment variable and add tests for olddefconfig,
savedefconfig, and the silent-conf path.

Signed-off-by: Pengpeng Hou <pengpeng@iscas.ac.cn>
Tested-by: Julian Braha <julianbraha@gmail.com>
Link: https://patch.msgid.link/20260611060000.23858-1-pengpeng@iscas.ac.cn
Signed-off-by: Nathan Chancellor <nathan@kernel.org>

bcmp() was removed in POSIX.1-2008.

This commit replaces bcmp() with memcmp(). This allows Kconfig to link
with C libraries that do not provide bcmp(), such as Android bionic
libc.

Signed-off-by: Thomas Meyer <thomas@m3y3r.de>
Reviewed-by: Miguel Ojeda <ojeda@kernel.org>
Reported-by: Abhigyan Ghosh <zscript.team.zs@gmail.com>
[masahiro: update commit description]
Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>

When conf_read_simple() is called with S_DEF_AUTO, it is meant to read
previous symbol values from include/config/auto.conf to determine which
include/config/* files should be touched.

This process should not modify the current symbol status in any way.
However, conf_touch_deps() currently invalidates all symbol values and
recalculates them, which is totally unneeded.

Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>

Most 'make *config' commands use .config as the base configuration file.

When .config does not exist, Kconfig tries to load a file listed in
KCONFIG_DEFCONFIG_LIST instead.

However, since commit b75b0a819af9 ("kconfig: change defconfig_list
option to environment variable"), warning messages have displayed an
incorrect file name in such cases.

Below is a demonstration using Debian Trixie. While loading
/boot/config-6.12.9-amd64, the warning messages incorrectly show .config
as the file name.

With this commit, the correct file name is displayed in warnings.

[Before]

  $ rm -f .config
  $ make config
  #
  # using defaults found in /boot/config-6.12.9-amd64
  #
  .config:6804:warning: symbol value 'm' invalid for FB_BACKLIGHT
  .config:9895:warning: symbol value 'm' invalid for ANDROID_BINDER_IPC

[After]

  $ rm -f .config
  $ make config
  #
  # using defaults found in /boot/config-6.12.9-amd64
  #
  /boot/config-6.12.9-amd64:6804:warning: symbol value 'm' invalid for FB_BACKLIGHT
  /boot/config-6.12.9-amd64:9895:warning: symbol value 'm' invalid for ANDROID_BINDER_IPC

Fixes: b75b0a819af9 ("kconfig: change defconfig_list option to environment variable")
Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>

Cache expression values to avoid recalculating them repeatedly.

Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>

These functions will be useful for other host programs.

Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>

Change the argument of sym_choice_default() to ease further cleanups.

Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>

This variable is unnecessary. Call conf_set_changed(true) directly.

Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>

Handling choices has always been in a PITA in Kconfig.

For example, fixes and reverts were repeated for randconfig with
KCONFIG_ALLCONFIG:

 - 422c809f03f0 ("kconfig: fix randomising choice entries in presence of KCONFIG_ALLCONFIG")
 - 23a5dfdad22a ("Revert "kconfig: fix randomising choice entries in presence of KCONFIG_ALLCONFIG"")
 - 8357b48549e1 ("kconfig: fix randomising choice entries in presence of KCONFIG_ALLCONFIG")
 - 490f16171119 ("Revert "kconfig: fix randomising choice entries in presence of KCONFIG_ALLCONFIG"")

As these commits pointed out, randconfig does not randomize choices when
KCONFIG_ALLCONFIG is used. This issue still remains.

[Test Case]

    choice
            prompt "choose"

    config A
            bool "A"

    config B
            bool "B"

    endchoice

    $ echo > all.config
    $ make KCONFIG_ALLCONFIG=1 randconfig

The output is always as follows:

    CONFIG_A=y
    # CONFIG_B is not set

Not only randconfig, but other all*config variants are also broken with
KCONFIG_ALLCONFIG.

With the same Kconfig,

    $ echo '# CONFIG_A is not set' > all.config
    $ make KCONFIG_ALLCONFIG=1 allyesconfig

You will get this:

    CONFIG_A=y
    # CONFIG_B is not set

This is incorrect because it does not respect all.config.

The correct output should be:

    # CONFIG_A is not set
    CONFIG_B=y

To handle user inputs more accurately, this commit refactors the code
based on the following principles:

 - When a user value is given, Kconfig must set it immediately.
   Do not defer it by setting SYMBOL_NEED_SET_CHOICE_VALUES.

 - The SYMBOL_DEF_USER flag must not be cleared, unless a new config
   file is loaded. Kconfig must not forget user inputs.

In addition, user values for choices must be managed with priority.
If user inputs conflict within a choice block, the newest value wins.
The values given by randconfig have lower priority than explicit user
inputs.

This commit implements it by using a linked list. Every time a choice
block gets a new input, it is moved to the top of the list.

Let me explain how it works.

Let's say, we have a choice block that consists of five symbols:
A, B, C, D, and E.

Initially, the linked list looks like this:

    A(=?) --> B(=?) --> C(=?) --> D(=?) --> E(=?)

Suppose randconfig is executed with the following KCONFIG_ALLCONFIG:

    CONFIG_C=y
    # CONFIG_A is not set
    CONFIG_D=y

First, CONFIG_C=y is read. C is set to 'y' and moved to the top.

    C(=y) --> A(=?) --> B(=?) --> D(=?) --> E(=?)

Next, '# CONFIG_A is not set' is read. A is set to 'n' and moved to
the top.

    A(=n) --> C(=y) --> B(=?) --> D(=?) --> E(=?)

Then, 'CONFIG_D=y' is read. D is set to 'y' and moved to the top.

    D(=y) --> A(=n) --> C(=y) --> B(=?) --> E(=?)

Lastly, randconfig shuffles the order of the remaining symbols,
resulting in:

    D(=y) --> A(=n) --> C(=y) --> B(=y) --> E(=y)
or
    D(=y) --> A(=n) --> C(=y) --> E(=y) --> B(=y)

When calculating the output, the linked list is traversed and the first
visible symbol with 'y' is taken. In this case, it is D if visible.

If D is hidden by 'depends on', the next node, A, is examined. Since
it is already specified as 'n', it is skipped. Next, C is checked, and
selected if it is visible.

If C is also invisible, either B or E is chosen as a result of the
randomization.

If B and E are also invisible, the linked list is traversed in the
reverse order, and the least prioritized 'n' symbol is chosen. It is
A in this case.

Now, Kconfig remembers all user values. This is a big difference from
the previous implementation, where Kconfig would forget CONFIG_C=y when
CONFIG_D=y appeared in the same input file.

The new appaorch respects user-specified values as much as possible.

Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>

Reduce the indentation level by continue'ing the loop earlier
if (!sym || sym_is_choice(sym)).

No functional change intended.

Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
Reviewed-by: Nicolas Schier <nicolas@fjasle.eu>