On 7/30/23 10:59, Masahiro Yamada wrote: > On Sat, Jul 29, 2023 at 12:23 AM Yoann Congal <yoann.congal@xxxxxxxx> wrote: >> Hi, Hi, >> While analyzing a Yocto bug[0] I think I've identified a problem in kconfig. >> The problem happens if you have a hex or int type config without a default value. >> Like this : >> config TEST_KCONFIG >> hex "Test kconfig" >> # No default value >> ... and try to start oldconfig with a closed stdin (like we have in Yocto): >> echo -n "" | make oldconfig >> >> When this happens, oldconfig prompts for the value of TEST_KCONFIG but stdin is closed it get the global default value : an empty string. This is not a valid hex/int value so it prompts again, hence the infinite loop. >> >> I'm having trouble pointing where the bug is exactly : >> * Should the global default value for hex/int be valid in their context? (like the minimal value of the range or 0/0x0) >> * Must all int/hex config provide a valid default value? (This is the case for hex config in the kernel). This would have to be documented somewhere (Some other KConfig implementation did [1]) > > Presumably, it is reasonable to require explicit 'default' for int/hex. > > Most of the int/hex entries in Linux are already doing it. Shouldn't this be documented somewhere? (Sorry if it already is, I could not find it) >> * Should all oldconfig/syncconfig/... exit with an error when trying to prompt on a closed stdin? (I might be able to send a patch for this one) > > No. > I have seen multiple scripts piping the 'yes' command to Kconfig. > There is no reason to prohibit pipe or redirection. I agree, I would not want to prohibit pipe or redirection. I'm specifically talking about a *closed* stdin. A closed stdin is a case were we're 100% sure that we'll never get a valid value. This is why I propose the following check : - closed stdin - default value is not valid (eg "" for a hex or int) If these two conditions are true when prompting, then exit with an error instead of what happens currently : starting an infinite loop. Would you accept something like this? > I think the fastest fix is to send a patch to U-Boot > to add a default for CONFIG_DEBUG_UART_BASE > (and more patches if there are other similar cases). Ok, I will try to do that. >> [0]: https://bugzilla.yoctoproject.org/show_bug.cgi?id=14136 >> [1]: https://docs.zephyrproject.org/1.14.0/guides/kconfig/index.html#redundant-defaults Thanks! -- Yoann Congal Smile ECS - Tech Expert
