Dne 17.5.2015 v 10:14 Martin Walch napsal(a): > From: Martin Walch <walch.martin@xxxxxx> > > expr_eliminate_dups2() in scripts/kconfig/expr.c applies two invalid > inference rules: > > (FOO || BAR) && (!FOO && !BAR) -> n > (FOO && BAR) || (!FOO || !BAR) -> y > > They would be correct in propositional logic, but this is a three-valued > logic, and here it is wrong in that it changes semantics. It becomes > immediately visible when assigning the value 1 to both, FOO and BAR: > > (FOO || BAR) && (!FOO && !BAR) > -> min(max(1, 1), min(2-1, 2-1)) = min(1, 1) = 1 > > while n evaluates to 0 and > > (FOO && BAR) || (!FOO || !BAR) > -> max(min(1, 1), max(2-1, 2-1)) = max(1, 1) = 1 > > with y evaluating to 2. Are you able to construct a testcase that triggers this bug? I haven't been successful: $ cat Kconfig.test config MODULES def_bool y option modules config FOO def_tristate m config BAR def_tristate m config TEST1 def_tristate (FOO || BAR) && (!FOO && !BAR) if TEST1 != m comment "TEST1 broken" endif config TEST2 def_tristate (FOO && BAR) || (!FOO || !BAR) if TEST2 != m comment "TEST2 broken" endif $ ./scripts/kconfig/conf Kconfig.test && cat .config * * Linux Kernel Configuration * # # configuration written to .config # # # Automatically generated file; DO NOT EDIT. # Linux Kernel Configuration # CONFIG_MODULES=y CONFIG_FOO=m CONFIG_BAR=m CONFIG_TEST1=m CONFIG_TEST2=m I'm all for eliminating unneeded code, but if it's meant to fix a bug as well, I'd like to understand the bug. thanks, Michal -- To unsubscribe from this list: send the line "unsubscribe linux-kbuild" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
