Masahiro Yamada <yamada.masahiro@xxxxxxxxxxxxx> writes: > 2018-08-14 19:38 GMT+09:00 Dirk Gouders <dirk@xxxxxxxxxxx>: >> Masahiro Yamada <yamada.masahiro@xxxxxxxxxxxxx> writes: >> >>> Currently, Kconfig does not report anything about the recursive >>> dependency where 'imply' keywords are involved. >>> >>> [Test Code] >>> >>> config A >>> bool "a" >>> >>> config B >>> bool "b" >>> imply A >>> depends on A >> >> Hello Masahiro, >> >> obviously, it is hard to find a reason why one wants to use dependencies >> like above but I also wonder how e.g. menuconfig handles this case: >> >> First, only "a" is visible, if I then select "a", "b" does not become >> visible but when I then reset "a" to "n", "b" becomes visible. If I then >> try to select "b", it becomes invisible... >> >> Perhaps it would be better to just error out instead of giving users the >> impression, Kconfig thinks such questionable behavior is OK. > > > Taking closer look at the code, the intention is 'recursive dependency > is error', > but the behavior changed probably by an accident. > > I fixed this: > https://patchwork.kernel.org/patch/10566301/ > >> Side note: perhaps, the documentation could be better when it comes to >> recursive dependencies. The documentation says "select" and >> "imply" can be used to specify lower limits whereas direct >> dependencies specify upper limits for symbol values and with >> this in mind, one might wonder why it is a problem to work >> with both limits in a recursive way. >> >> Not very unlikely that it is just me who still has to >> understand recursive dependencies or problems with reading >> English text, though. > > > To avoid confusion, two things should be discussed separately: > > [1] Unmet dependency > This is caused by a conflict between the upper limit from 'depends on' > and the lower limit from 'select'. > > This issue does not happen for 'imply' because the upper limit > specified by 'imply' is weaker. > > > [2] Recursive depenency > > This can happen for any combination of 'depends on', > 'select', 'imply', 'if', 'default', etc. Yes, this is probably just a subject that I still have to get a deeper understanding for, hence I am easyly confused when faced with contradicting information. >> What definitely seems to get void with your patches is item c) in >> "Practical solutions to kconfig recursive issue" in >> Documentation/kbuild/kconfig-language: >> >> c) Consider the use of "imply" instead of "select" > > > I do not know why commit 237e3ad0f195d8 added this line. > > > Actually, I was also confused. > > I sent v2 based on your feedback. Thanks for your responses, making that all more understandable. Dirk > > >> Dirk >> >>> 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 report 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 is hit. This will be solved by >>> the next commit. >>> >>> Signed-off-by: Masahiro Yamada <yamada.masahiro@xxxxxxxxxxxxx> >>> --- >>> >>> scripts/kconfig/symbol.c | 9 +++++++-- >>> 1 file changed, 7 insertions(+), 2 deletions(-) >>> >>> diff --git a/scripts/kconfig/symbol.c b/scripts/kconfig/symbol.c >>> index 4ec8b1f..7de7463a 100644 >>> --- a/scripts/kconfig/symbol.c >>> +++ b/scripts/kconfig/symbol.c >>> @@ -1098,7 +1098,7 @@ static void sym_check_print_recursive(struct symbol *last_sym) >>> sym->name ? sym->name : "<choice>", >>> next_sym->name ? next_sym->name : "<choice>"); >>> } else { >>> - fprintf(stderr, "%s:%d:\tsymbol %s is selected by %s\n", >>> + fprintf(stderr, "%s:%d:\tsymbol %s is selected or implied by %s\n", >>> prop->file->name, prop->lineno, >>> sym->name ? sym->name : "<choice>", >>> next_sym->name ? next_sym->name : "<choice>"); >>> @@ -1161,8 +1161,13 @@ static struct symbol *sym_check_sym_deps(struct symbol *sym) >>> if (sym2) >>> goto out; >>> >>> + sym2 = sym_check_expr_deps(sym->implied.expr); >>> + if (sym2) >>> + goto out; >>> + >>> for (prop = sym->prop; prop; prop = prop->next) { >>> - if (prop->type == P_CHOICE || prop->type == P_SELECT) >>> + if (prop->type == P_CHOICE || prop->type == P_SELECT || >>> + prop->type == P_IMPLY) >>> continue; >>> stack.prop = prop; >>> sym2 = sym_check_expr_deps(prop->visible.expr);
