[U-Boot] [PATCH v1 1/4] Kconfig: Enable usage of escape char '\' in string values

Masahiro Yamada
2015-05-13T01:34:29Z

Hi, Simon, Stefan,

2015-05-12 7:41 GMT+09:00 Simon Glass <sjg@chromium.org>:
> Hi Stefan,
>
> On 11 May 2015 at 07:27, Stefan Roese <mail@roese.nl> wrote:
>> Hi Simon, Hi Masahiro,
>>
>>
>> On 11.05.2015 09:58, Stefan Roese wrote:
>>>
>>> On 10.05.2015 16:48, Simon Glass wrote:
>>>>
>>>> On 7 May 2015 at 06:13, Stefan Roese <sr@denx.de> wrote:
>>>>>
>>>>> I might have missed something, but I failed to use the escape char '\'
>>>>> in strings. To pass a printf format string like "foo %d bar\n" via
>>>>> Kconfig to the code.
>>>>>
>>>>> Right now its not possible to use the escape character '\' in Kconfig
>>>>> string values correctly to e.g. set this string value "test output\n".
>>>>> The '\n' will be converted to 'n'.
>>>>>
>>>>> The current implementation removes some of the '\' chars from the input
>>>>> string in conf_set_sym_val(). Examples:
>>>>>
>>>>> '\' -> ''
>>>>> '\\' -> '\'
>>>>> '\\\' -> '\'
>>>>> '\\\\' -> '\\'
>>>>> ...
>>>>>
>>>>> And then doubles the backslash chars in the output string in
>>>>> sym_escape_string_value(). Example:
>>>>>
>>>>> '\' -> '' -> ''
>>>>> '\\' -> '\' -> '\\'
>>>>> '\\\' -> '\' -> '\\'
>>>>> '\\\\' -> '\\' -> '\\\\'
>>>>> ...
>>>>>
>>>>> As you see in these examples, its impossible to generate a single '\'
>>>>> charater in the output string as its needed for something like '\n'.
>>>>>
>>>>> This patch now changes this behavior to not drop some backslashes in
>>>>> conf_set_sym_val() and to not add new backslashes in the resulting
>>>>> output string. Removing the function sym_escape_string_value()
>>>>> completely as its not needed anymore.
>>>>>
>>>>> Signed-off-by: Stefan Roese <sr@denx.de>
>>>>> Cc: Masahiro Yamada <yamada.masahiro@socionext.com>
>>>>> Cc: Simon Glass <sjg@chromium.org>
>>>>> ---
>>>>>
>>>>> scripts/kconfig/confdata.c | 20 +++++++++-----------
>>>>> scripts/kconfig/symbol.c | 43
>>>>> -------------------------------------------
>>>>> 2 files changed, 9 insertions(+), 54 deletions(-)
>>>>
>>>>
>>>> This looks right to me. But I do see one problem - the default string
>>>> for CONFIG_AUTOBOOT_PROMPT appears as:
>>>>
>>>> "Autoboot in %d secondsn"
>>>>
>>>> so something is still removing the \ in the Kconfig default;
>>>
>>>
>>> Right. Thanks for spotting. I'll fix this in v3.
>>
>>
>> I could easily change the default string in the Kconfig file to "Autoboot in
>> %d seconds\\n". This works. But its a different syntax regarding using the
>> escape character backslash compared to editing the .config file or editing
>> the string in "make menuconfig etc...". So I hesitate to "fix" it this way.
>>
>> Unfortunately fixing this issue in the code is not that easy. At least not
>> for me. As the default values of the "string values" are set in the
>> conf_parse() function (in scripts/kconfig/zconf.y). And I really have
>> absolutely no experience with yacc / bison. Perhaps one of you guys has a
>> quick fix to make this default value of strings compatible again so that
>> this additional '\' is not needed in the Kconfig file?
>
> Well I am familiar with those tools but I think Masahiro probably
> knows a lot more here.

I am not so familiar with Bison, and I am getting a bit busy these days.
So, I cannot find time to take a close look. Sorry.

If Simon (or someone else) could follow it up, that'd be nice.

BTW, if you have already figured out that conf_parse() is the cause of
the problem,
you do not have to invoke Bison.

Bison does not touch the C part.
conf_parse() is just copied verbatim from zconf.y to zconf.tab.c_shipped.

You can modify conf_parse() exactly in the same way in both of them.

--
Best Regards
Masahiro Yamada