Re: A couple of config(1) questions

[Paul Goyette <paul%vps1.whooppee.com@localhost>]

On Sun, 10 May 2015, Michael van Elst wrote:

> > Just how complex can these expressions be?  For example, can I use
> > 	(a | b) & (x | y | z)
> > with parentheses?
>
>
> config uses a yacc grammar (src/usr.bin/config/gram.y):

<snip>

> /* zero or more flags for a file */
> fflags:
>          /* empty */                   { $$ = 0; }
>        | fflags fflag                  { $$ = $1 | $2; }
> ;
>
> /* one flag for a file */
> fflag:
>          NEEDS_COUNT                   { $$ = FI_NEEDSCOUNT; }
>        | NEEDS_FLAG                    { $$ = FI_NEEDSFLAG; }
> ;
>
> /* extra compile directive for a source file */
> rule:
>          /* empty */                   { $$ = NULL; }
>        | COMPILE_WITH stringvalue      { $$ = $2; }
> ;
>
>
> So it's the options that can be an expression. [rule] is
> the keyword 'compile-with' followed by a string holding
> a compiler command that is used in the generated Makefile.
> Without a rule, config generates the rule ${NORMAL_<upper-case-suffix>}
> I.e. ${NORMAL_C} for a C file. That variable is defined in
> sys/conf/Makefile.kern.inc.

Kewl - thanks for helping me figure out how to parse yacc's grammar!


> The condexpr used for fopts can handle the operators |,& and
> ! (or,and,not) and allows parenthesis, i.e. (a | b) & (x | y | z)
> works fine. But the parser does not handle negations of sub-expressions
> like !( a | b ).

Yeah, what I wanted does indeed work.

<snip>

> > Question 2:  does config(1) support '\' at the end of a physical line to
> > indicate line continuation?  (If the complex boolean expression above is
> > supported, I'm likely to have a longer-than-80-char command!)
>
> The config parser uses a different syntax to handle continuation
> lines. From config(9):
>
>     Each device definition file consists of a list of statements, typically
>     one per line.  Comments may be inserted anywhere using the ``#''
>     character, and any line that begins with white space continues the
>     previous line.

Thanks - I missed that while reading the man page.


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