[gentoo-dev] RFC: CONFIG_CHECK_FATAL, making CONFIG_CHECKS fatal by default

[Robin H. Johnson]

I'm raising this patch because of the recent spate of bugs with the
latest udev  that now fails to boot your system if CONFIG_DEVTMPFS is
not available in your kernel.

Bugs: 408947, 409393, 437320, 453074	

CONFIG_CHECK has not been fatal for some years now, because there turned
out to be some cases where it cannot detect what the system really has
[1], or what is returned is wrong [2].

However, while this is has been superb in helping those corner-cases,
the fallout is that users frequently ignore the non-fatal warnings that
a configuration option is needed to run a binary later, and end up with
weird breakage.

This patch introduces a new option, CONFIG_CHECK_FATAL, defaulting to
enabled, that explicitly causes a die if:
- CONFIG_CHECK cannot be performed successfully.
- Any CONFIG_CHECK options fail.

For the aforementioned corner cases, those environments are used to
customizing their make.conf heavily, and they should add:
CONFIG_CHECK_FATAL=0

This patch does NOT change the handling of ~/tilde in CONFIG_CHECK
- options that are required at compile-time MUST NOT use ~/tilde.
- options that are only required at run-time MUST include the ~/tilde.

Footnotes:
1. If you are using a VM environment, where the kernel is provided
   outside of your VM, and you don't have kernel sources, or
   /proc/config.gz, you CANNOT detect what options the kernel is
   configured with.
2. Building stages for example. You may have /proc bind-mounted from the
   host system, but it does not reflect the environment you are building
   for.

-- 
Robin Hugh Johnson
Gentoo Linux: Developer, Trustee & Infrastructure Lead
E-Mail     : robbat2@g.o
GnuPG FP   : 11ACBA4F 4778E3F6 E4EDF38E B27B944E 34884E85