linux

kconfig: add optional warnings for changed input values 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> 2026-06-11 14:00:00 +08:00