Messages in this thread | | | Date | Thu, 6 Dec 2012 01:07:04 +0100 | Subject | kbuild: Invalid configuration generated for dependent choices by 'conf' but not by 'mconf', with reason | From | Ulf Magnusson <> |
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Hi,
Consider the following Kconfig file:
config MODULES def_bool y
choice tristate "C1" config A tristate "A" config B tristate "B" endchoice
choice bool "C2" if A config C bool "C" config D bool "D" endchoice
When this Kconfig file is used with a configuration file containing just "CONFIG_A=y", conf generates the following invalid configuration:
CONFIG_MODULES=y CONFIG_A=m # CONFIG_B is not set CONFIG_C=y # CONFIG_D is not set
mconf on the other hand generates the correct configuration:
CONFIG_MODULES=y CONFIG_A=y # CONFIG_B is not set CONFIG_C=y # CONFIG_D is not set
To see this, compare the .config files generated by the following commands:
$ scripts/kconfig/conf --defconfig=bug_config bug_Kconfig
$ cp bug_config .config $ scripts/kconfig/mconf bug_Kconfig
The root cause of the problem is the sym_calc_value(csym) call at the end of conf_set_all_new_symbols(). Since the second 'choice' depends on A, that call causes the value of A to be calculated. But this also causes SYMBOL_VALID to be set on A, preventing it from being reevaluated later when the configuration is written in conf_write(). This reevaluation is required to get the correct value since only by then will the choice have SYMBOL_DEF_USER set on it (set in set_all_choice_values()).
Some possible fixes: (1) Add another sym_clear_all_valid() call at the end of conf_set_all_new_symbols(). This is kinda wasteful. (2) Just randomize_choice_values() seems to actually need the sym_calc_value(csym). It could probably be moved into that function, perhaps doing the additional sym_clear_all_valid() there unless there's something neater you could do.
It would probably be safer if someone more familiar with the randomization stuff wrote the actual patch.
Linux version is 3.7.0-rc4, though this bug has likely been around a while.
/Ulf
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