d9be8eeab0
[ 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>
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| Documentation | ||
| LICENSES | ||
| arch | ||
| block | ||
| certs | ||
| crypto | ||
| drivers | ||
| fs | ||
| include | ||
| init | ||
| io_uring | ||
| ipc | ||
| kernel | ||
| lib | ||
| mm | ||
| net | ||
| rust | ||
| samples | ||
| scripts | ||
| security | ||
| sound | ||
| tools | ||
| usr | ||
| virt | ||
| .clang-format | ||
| .cocciconfig | ||
| .get_maintainer.ignore | ||
| .gitattributes | ||
| .gitignore | ||
| .mailmap | ||
| .rustfmt.toml | ||
| COPYING | ||
| CREDITS | ||
| Kbuild | ||
| Kconfig | ||
| MAINTAINERS | ||
| Makefile | ||
| README | ||
README
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 Restructured Text 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.