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. > 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. > 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); -- Best Regards Masahiro Yamada
