lint: warn about extern declarations outside headers

https://mail-index.netbsd.org/tech-userlevel/2023/03/15/msg013727.html

tests/lint: add more tests for array/enum mismatch

lint: recognize enum constant named 'max' as a count of values

Seen in external/bsd/mdocml/dist/mdoc.h(50).

tests/lint: add more tests for enum/array mismatch

lint: add quotes around a few more placeholders in messages

lint: do not warn about array size mismatch in array[(int)enum]

The cast to 'int' explicitly converts the type away from being an enum.

lint: in the check for array[enum], allow enum constant NUM

When an enum type defines a constant NUM_VALUES, this constant is
usually not part of the enum values available to the application but
rat

lint: in the check for array[enum], allow enum constant NUM

When an enum type defines a constant NUM_VALUES, this constant is
usually not part of the enum values available to the application but
rather a handy place for defining the number of other enum values. Don't
warn about this case.

Seen in openpam_impl.h and several other places.

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lint: fix invalid memory access in array[enum] check

Lint checks whether in an expression 'array[enum]', the array size
matches the value of the maximum enum constant.

The previous tests for this c

lint: fix invalid memory access in array[enum] check

Lint checks whether in an expression 'array[enum]', the array size
matches the value of the maximum enum constant.

The previous tests for this check were missing the case where an enum
name was explicitly cast to an integer type and then used as an array
index. In this situation, the resulting type of the array index is a
plain 'int' without any information about its previous 'enum' history.

An entirely different case is when the 'enum' is implicitly converted to
an integer type, as in the test color_name_too_many. There, for the
final type of the array index, rn->tn_type->t_is_enum is true, which
means that rn->tn_type->t_enum is properly filled.

The bug was a simple typo, I had forgotten a tn_left indirection, which
is necessary to get the type before the implicit conversion.

Found and reported by Christos, triggered by src/lib/libperfuse/ops.c
1.89 line 1226 expression 'VTTOIF(vap->va_type)'.

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lint: warn if an enum name is used for mismatched array access

This helps to keep the enum definition and the straight-forward
implementation of a to_string or name function in sync.

The test for m

lint: warn if an enum name is used for mismatched array access

This helps to keep the enum definition and the straight-forward
implementation of a to_string or name function in sync.

The test for message 241 had to be adjusted because of exactly this bug.
That test defined a bit mask enum but accessed it like a value enum
type.

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