Re: escape strings in grub.cfg

[Colin Watson]

On Sat, Apr 10, 2010 at 10:10:15PM +0100, Carles Pina i Estany wrote:
> Last weekend, the Asturian team found a bug in Grub. Thanks for the
> debugging. The string that appears in grub.cfg for "Loading the initram"
> in Asturian is "Cargando'l discu RAM inicial...". So grub.cfg looks
> like:
>         echo    Cargando'l discu RAM inicial...
> 
> This is syntactically invalid because the character "'".
> 
> Easy work around: generate the line like:
>       echo    "Cargando'l discu RAM inicial..."
> 
> New problem: in some language, this string could have a double quote
> inside.
> 
> New solution: escape the double quotes strings when they are used in
> gettext and always use these strings with double quotes.
> 
> See the attached patch.
> 
> I'm not convinced of the patch, does anybody has a cleaner idea/patch?

This doesn't cover everything - you've just moved the goalposts a bit.
Here's the relevant bit of the lexer:

<SQUOTE>{
  \'            {
                  yy_pop_state (yyscanner);
                  ARG (GRUB_SCRIPT_ARG_TYPE_SQSTR);
                }
  [^\']+        { COPY (yytext, yyleng); }
}

<DQUOTE>{
  \"            {
                  yy_pop_state (yyscanner);
                  ARG (GRUB_SCRIPT_ARG_TYPE_DQSTR);
                }
  \$            {
                  yy_push_state (VAR, yyscanner);
                  ARG (GRUB_SCRIPT_ARG_TYPE_DQSTR);
                }
  \\\\          { COPY ("\\", 1); }
  \\\"          { COPY ("\"", 1); }
  \\\n          { /* ignore */ }
  [^\"$\\\n]+   { COPY (yytext, yyleng); }
  (.|\n)        { COPY (yytext, yyleng); }
}

In other words, only ' is special (as a terminator) when reading a
single-quoted string, and the sequences " $ \\ \" \n are special inside
a double-quoted string.  (Incidentally, I think there's another bug
here; if $ is special, \$ should be special as well.)

Given this, wouldn't you be better off using single-quotes instead?
You'd then end up with:

          echo    'Cargando'\''l discu RAM inicial...'

... where the construction used to escape ' is "close quotes, literal ',
reopen quotes".  (Tested in grub-emu.)

> +gettext_escape_double_quotes ()
> +{
> +  echo -n $(gettext $@) | sed 's/\"/\\\"/'
> +}

This is underquoted, and in any case the 'echo -n' is redundant since
gettext itself already writes to standard output and $() substitution
strips trailing newlines.  $@ requires special treatment, and that sed
s/// command needs /g.  With my suggestion, I'd recommend:

  gettext_quoted () {
    gettext "$@" | sed "s/'/'\\\\''/g"
  }

... and then make sure it's enclosed in '' rather than "" wherever it's
used (or modify the sed to put single-quotes at the start and end, if
that works out neater).

-- 
Colin Watson                                       address@hidden