G'day,
I like the basic idea here, and I'm pleased that someone has the courage to
tackle some of the brokenness of the kconfig language (if only because it
will provide me with a precedent when I try to submit some of my patches ;-).
I was a bit worried when I first saw the patch (after all, kconfig is held
together with spit and string) but on careful reading it's mostly doing the
right thing. Mostly.
Peter Samuelson wrote:
>
> [Kai Germaschewski]
> > > As you're hacking Configure anyway, what about "fixing"
> > >
> > > dep_tristate ' ..' CONFIG_FOO $CONFIG_BAR,
>
> [I wrote]
> > I've thought about that many times. I think the cleanest solution is
> > to deprecate the '$' entirely:
> >
> > dep_tristate ' ..' CONFIG_FOO CONFIG_BAR
>
> This applies to 2.4.20pre and (except changelog bits) to 2.5.30 with
> offsets.
You're willing to potentially perturb 2.4?
> I still haven't touched xconfig, because frankly it scares
> me. The tkparse.c vs Peter match is well underway, stay tuned..
Good luck, it scares me too.
> --- 2.4.20pre1/Documentation/kbuild/config-language.txt 2002-02-25 13:37:51.000000000 -0600
> +++ 2.4.20pre1p/Documentation/kbuild/config-language.txt 2002-08-08 23:10:44.000000000 -0500
> @@ -84,8 +84,17 @@
> to generate dependencies on individual CONFIG_* symbols instead of
> making one massive dependency on include/linux/autoconf.h.
>
> - A /dep/ is a dependency. Syntactically, it is a /word/. At run
> - time, a /dep/ must evaluate to "y", "m", "n", or "".
> + A /tristate/ is a single character in the set {"y","m","n"}.
> +
> + A /dep/ is a dependency. Syntactically, it is a /word/. It is
> + either a /tristate/ or a /symbol/ (with an optional, but
> + deprecated, prefix "$"). At run time, the /symbol/, if present,
> + is expanded to produce a /tristate/. If the /symbol/ has not been
> + defined, the /tristate/ will be "n".
The last statement is inconsistent with the shell code and the explanations of
the dep_* statements, which sensibly preserve the current semantics where
an undefined symbol has a distinct fourth value which is not y, m or n.
I'm pleased to see that you have preserved those semantics. There are many
places in the corpus where a dep_* lists as a dependency a variable which is
not defined until later, or is only defined in some architectures, or is never
defined. Earlier today I tweaked up gcml2 to detect them and found 260 in
2.5.29.
> + In addition, the /dep/ may have a prefix "!", which negates the
> + sense of the /tristate/: "!y" and "!m" reduce to "n", and "!n"
> + reduces to "y".
Perhaps "negates" isn't quite the right word in four-state logic.
> --- 2.4.20pre1/scripts/Configure 2001-07-02 15:56:40.000000000 -0500
> +++ 2.4.20pre1p/scripts/Configure 2002-08-08 22:31:49.000000000 -0500
> @@ -232,6 +241,28 @@
> }
>
> #
> +# dep_calc reduces a dependency line down to a single char [ymn]
> +#
> +function dep_calc () {
> + local neg arg
> + cur_dep=y # return value
> + for arg; do
> + neg=;
> + case "$arg" in
> + !*) neg=N; arg=${arg#?} ;;
> + esac
> + case "$arg" in
> + y|m|n) ;;
> + *) arg=$(eval echo \$$arg) ;;
Don't you want to check at this point that arg starts with CONFIG_?
Also, how about quoting \$$arg ?
> + esac
> + case "$neg$arg" in
> + m) cur_dep=m ;;
> + n|Ny|Nm) cur_dep=n; return ;;
> + esac
When CONFIG_FOO is undefined, !CONFIG_FOO and CONFIG_FOO are both ignored,
which is not consistent with the mention of "!" in the explanations for the
dep_* statements. Perhaps you need to more carefully define the semantics
of the ! prefix.
Greg.
--
the price of civilisation today is a courageous willingness to prevail,
with force, if necessary, against whatever vicious and uncomprehending
enemies try to strike it down. - Roger Sandall, The Age, 28Sep2001.
Greg Banks <[email protected]> writes:
|> > --- 2.4.20pre1/scripts/Configure 2001-07-02 15:56:40.000000000 -0500
|> > +++ 2.4.20pre1p/scripts/Configure 2002-08-08 22:31:49.000000000 -0500
|> > @@ -232,6 +241,28 @@
|> > }
|> >
|> > #
|> > +# dep_calc reduces a dependency line down to a single char [ymn]
|> > +#
|> > +function dep_calc () {
|> > + local neg arg
|> > + cur_dep=y # return value
|> > + for arg; do
|> > + neg=;
|> > + case "$arg" in
|> > + !*) neg=N; arg=${arg#?} ;;
|> > + esac
|> > + case "$arg" in
|> > + y|m|n) ;;
|> > + *) arg=$(eval echo \$$arg) ;;
|>
|> Don't you want to check at this point that arg starts with CONFIG_?
|> Also, how about quoting \$$arg ?
The Right Way to write that is like this, assuming that $arg has already
been verified to be a valid identifier:
eval arg=\$$arg
No need for further quoting.
Andreas.
--
Andreas Schwab, SuSE Labs, [email protected]
SuSE Linux AG, Deutschherrnstr. 15-19, D-90429 N?rnberg
Key fingerprint = 58CA 54C7 6D53 942B 1756 01D3 44D5 214B 8276 4ED5
"And now for something completely different."
[Greg Banks]
> I like the basic idea here, and I'm pleased that someone has the
> courage to tackle some of the brokenness of the kconfig language (if
> only because it will provide me with a precedent when I try to
> submit some of my patches ;-).
Thanks for the feedback. (:
> > This applies to 2.4.20pre and (except changelog bits) to 2.5.30 with
> > offsets.
>
> You're willing to potentially perturb 2.4?
This stuff is trivial enough, and easy enough to test, that I think it
could go in 2.4, yes. Obviously xconfig would need to be dealt with
in sync with the others, which I'm not doing during the prototyping /
idea-mongering stage.
> The last statement is inconsistent with the shell code and the
> explanations of the dep_* statements, which sensibly preserve the
> current semantics where an undefined symbol has a distinct fourth
> value which is not y, m or n.
>
> I'm pleased to see that you have preserved those semantics. There
> are many places in the corpus where a dep_* lists as a dependency a
> variable which is not defined until later, or is only defined in
> some architectures, or is never defined. Earlier today I tweaked up
> gcml2 to detect them and found 260 in 2.5.29.
You give me too much credit. The main motivation for dropping the '$'
was to make possible the "" == "n" semantics. That the patch failed
to do so was accident, not design.
I know the current behavior is documented, but I had thought this was
because changing the behavior was not feasible due to our Bash-based
"JIT parsers". Can you provide a rationale for why the current
behavior is desirable? It seems to me that it only encourages buggy
Config.in code (since "" == "n" in other contexts like the #defines),
and I don't see any benefits other than that it's the status quo.
[Not to demean the status quo - in 2.4 it is probably appropriate.]
> > + In addition, the /dep/ may have a prefix "!", which negates the
> > + sense of the /tristate/: "!y" and "!m" reduce to "n", and "!n"
> > + reduces to "y".
>
> Perhaps "negates" isn't quite the right word in four-state logic.
I wasn't sure what else to call it. Besides, as explained above, it's
intended (rightly or wrongly) to be 3-state logic, where two states
represent a form of "true". (:
Perhaps "the /dep/ may have a prefix "!", which transforms the
/tristate/ as follows: ..." This is particularly appropriate in light
of Roman's argument (which I buy) in favor of "!m" == "m".
> > +function dep_calc () {
> > + local neg arg
> > + cur_dep=y # return value
> > + for arg; do
> > + neg=;
> > + case "$arg" in
> > + !*) neg=N; arg=${arg#?} ;;
> > + esac
> > + case "$arg" in
> > + y|m|n) ;;
> > + *) arg=$(eval echo \$$arg) ;;
>
> Don't you want to check at this point that arg starts with CONFIG_?
> Also, how about quoting \$$arg ?
I suppose one could add sanity checks / diagnostics, but there are no
other valid cases, so that's all they would be. I'm not really trying
to produce a config.in 'lint' - leave that to the static parsers like
gcml2, xconfig and mconfig.
Peter