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

Stefan Roese
2015-05-11T13:27:58Z

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?

Thanks,
Stefan