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8bfd6f0923
Kconfig simplifies expressions, but redundant '&&' and '||' operators
involving constant symbols 'y' and 'n' are sometimes trimmed and
sometimes not.
[Test Code]
config DEP
def_bool y
config A
bool "A"
depends on DEP && y
config B
bool "B"
depends on DEP && y && y
[Result]
$ make helpnewconfig
[ snip ]
-----
There is no help available for this option.
Symbol: A [=n]
Type : bool
Defined at Kconfig:4
Prompt: A
Depends on: DEP [=y] && y [=y]
Location:
-> A (A [=n])
-----
-----
There is no help available for this option.
Symbol: B [=n]
Type : bool
Defined at Kconfig:8
Prompt: B
Depends on: DEP [=y]
Location:
-> B (B [=n])
-----
The dependency for A, 'DEP && y', remains as-is, while that for B,
'DEP && y && y', has been reduced to 'DEP'.
Currently, expr_eliminate_dups() calls expr_eliminate_yn() only when
trans_count != 0, in other words, only when expr_eliminate_dups1() has
trimmed at least one leaf. It fails to trim a single '&& y', etc.
To fix this inconsistent behavior, expr_eliminate_yn() should be called
at least once even if no leaf has been trimmed.
Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
Linux kernel
============
There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.
In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``. The formatted documentation can also be read online at:
https://www.kernel.org/doc/html/latest/
There are various text files in the Documentation/ subdirectory,
several of them using the reStructuredText markup notation.
Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.