kconfig: The error message is misleading when values are out-of-range

[SebastianBoe]

Hi,

the error message is misleading when values are out-of-range. E.g.

CONFIG_FOO=5

 config FOO
     range 0 3

Should trigger an error about the value being out-of-range, but instead it triggers a warning about dependencies.

warning: FOO was assigned the value "5" but got the value "0" -- check dependencies

[ulfalizer]

Might be tricky to infer that it was specifically due to the range from kconfig.py. Maybe something like this would point people in the right direction though:

msg = "warning: {} was assigned..."
if sym.ranges:
    msg += " and range constraints"
print(msg, ...)

The behavior of range is a bit wonky in general. default 5 is clamped to 3, while 5 as a user value causes the lower end of the range to be used. It's only done like that for compatibility with the C implementation. It would make more sense to clamp both to 3.

[ulfalizer]

I tweaked https://github.com/ulfalizer/Kconfiglib/blob/master/examples/merge_config.py to also print the location of the symbol ("FOO (defined at bar/Kconfig:73) was assigned...") btw. That might be nice to have in the Zephyr version too.

[SebastianBoe]

The behavior of range is a bit wonky in general. default 5 is clamped to 3, while 5 as a user value causes the lower end of the range to be used. It's only done like that for compatibility with the C implementation. It would make more sense to clamp both to 3.

I'd say it would make more sense to error-out than to do any clamping.

The docs don't mention anything about clamping, but instead state that the user must
stay within the range. Which implies to me that an error should be triggered.

• numerical ranges: "range" ["if" ]
  This allows to limit the range of possible input values for int
  and hex symbols. The user can only input a value which is larger than
  or equal to the first symbol and smaller than or equal to the second
  symbol.

[SebastianBoe]

I am happy with any solution that makes the user realize he is out-of-range.

[SebastianBoe]

msg = "warning: {} was assigned..."
if sym.ranges:
    msg += " and range constraints"
print(msg, ...)

This should work.

[ulfalizer]

A warning from Kconfiglib might be nice at least, when it detects that the user value is out-of-range. Should check that it doesn't get super spammy for the Linux kernel configs though.

Should get back to finding an accountant now. Code is more fun than IRL...

[ulfalizer]

I added a warning for it: ulfalizer/Kconfiglib@7ba79ca

[SebastianBoe]

@ulfalizer : Much better, I would prefer an error, but if there are unresolvable compatibility issues with Linux then a warning is good enough.