Masahiro Yamada 5e6d87eabf kconfig: remove wrong expr_trans_bool()
[ Upstream commit 77a92660d8fe8d29503fae768d9f5eb529c88b36 ]

expr_trans_bool() performs an incorrect transformation.

[Test Code]

    config MODULES
            def_bool y
            modules

    config A
            def_bool y
            select C if B != n

    config B
            def_tristate m

    config C
            tristate

[Result]

    CONFIG_MODULES=y
    CONFIG_A=y
    CONFIG_B=m
    CONFIG_C=m

This output is incorrect because CONFIG_C=y is expected.

Documentation/kbuild/kconfig-language.rst clearly explains the function
of the '!=' operator:

    If the values of both symbols are equal, it returns 'n',
    otherwise 'y'.

Therefore, the statement:

    select C if B != n

should be equivalent to:

    select C if y

Or, more simply:

    select C

Hence, the symbol C should be selected by the value of A, which is 'y'.

However, expr_trans_bool() wrongly transforms it to:

    select C if B

Therefore, the symbol C is selected by (A && B), which is 'm'.

The comment block of expr_trans_bool() correctly explains its intention:

  * bool FOO!=n => FOO
    ^^^^

If FOO is bool, FOO!=n can be simplified into FOO. This is correct.

However, the actual code performs this transformation when FOO is
tristate:

    if (e->left.sym->type == S_TRISTATE) {
                             ^^^^^^^^^^

While it can be fixed to S_BOOLEAN, there is no point in doing so
because expr_tranform() already transforms FOO!=n to FOO when FOO is
bool. (see the "case E_UNEQUAL" part)

expr_trans_bool() is wrong and unnecessary.

Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
Acked-by: Randy Dunlap <rdunlap@infradead.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
2024-07-25 09:49:11 +02:00
..
2022-08-07 21:30:36 +02:00
2022-09-28 09:02:20 +02:00
2023-12-13 18:39:19 +01:00
2022-09-28 09:02:20 +02:00
2022-03-21 08:13:03 -07:00
2022-09-28 09:02:20 +02:00
2022-10-03 14:03:19 -07:00
2022-09-26 10:13:13 -07:00
2022-03-07 13:54:59 +01:00
2020-12-08 23:30:04 +09:00
2020-12-08 23:30:04 +09:00
2021-05-03 17:23:06 -06:00