On 3/20/20 11:46 AM, Richard Sandiford wrote:
Martin Sebor <mse...@gmail.com> writes:
On 3/17/20 5:52 AM, Richard Sandiford wrote:
Lewis Hyatt <lhy...@gmail.com> writes:
On Mon, Mar 16, 2020 at 06:11:08PM +0000, Richard Sandiford wrote:
Lewis Hyatt via Gcc-patches <gcc-patches@gcc.gnu.org> writes:
...
FWIW there are three other options currently affected by this change
(-Wimplicit-fallthrough, -fcf-protection, and -flive-patching). The change for
-Wimplicit-fallthrough I think is particularly helpful:
-Wimplicit-fallthrough Same as -Wimplicit-fallthrough=. Use the latter
option instead.
becomes
-Wimplicit-fallthrough Same as -Wimplicit-fallthrough=3 (or, in negated
form, -Wimplicit-fallthrough=0).
I also see:
- -ftail-call-workaround Same as -ftail-call-workaround=. Use the latter
option instead.
+ -ftail-call-workaround Same as -ftail-call-workaround=1 (or, in negated
form, -ftail-call-workaround=0).
-ftail-call-workaround=<0,2> Disallow tail call optimization when a
calling routine may have omitted character lengths.
...
--imacros Same as -imacros. Use the latter option
instead.
--imacros= Same as -imacros. Use the latter option
instead.
--include Same as -include. Use the latter option
instead.
- --include-barrier Same as -I. Use the latter option instead.
+ --include-barrier Same as -I-.
--include-directory Same as -I. Use the latter option instead.
--include-directory-after Same as -idirafter. Use the latter option
instead.
--include-directory-after= Same as -idirafter. Use the latter option
instead.
...
- -Wnormalized Same as -Wnormalized=. Use the latter option
instead.
+ -Wnormalized Same as -Wnormalized=nfc (or, in negated form,
-Wnormalized=none).
-Wnormalized=[none|id|nfc|nfkc] Warn about non-normalized Unicode strings.
I agree all of these look like improvements, especially the
--include-barrier one. But I think the include ones also show
that the "Use the latter option instead." decision is independent
of whether the option is defined to be an alias.
Gah, I meant an Alias() with an argument here.
FWIW, there's also:
Wmissing-format-attribute
C ObjC C++ ObjC++ Warning Alias(Wsuggest-attribute=format)
;
which still ends up as:
-Wmissing-format-attribute Same as -Wsuggest-attribute=format. Use the
latter option instead.
Not really my area though, so I don't have any specific suggestion
about how to separate the cases.
Right, sorry, in my first email I only mentioned the options output by
--help=common, but there were a few more as well. Thanks very much for trying
it out and for the feedback.
The rule I implemented was to change the help output for all alias options
with no documentation if they also specify the extra 2nd option (or 2nd and
3rd options) to the Alias directive. For example, -include-barrier is like this:
-include-barrier C ObjC C++ ObjC++ Alias(I, -)
It serves to provide the argument '-' to the option '-I', so it is eligible for
the new text. The others are like this one:
-include-directory-after C ObjC C++ ObjC++ Separate Alias(idirafter)
MissingArgError(missing path after %qs)
Since that one doesn't pass the extra args to Alias, I interpreted it to
mean this is the case for which the "Use the latter option" directive was
intended to apply. (-idirafter has been designated as preferable to
-include-directory-after).
Yeah, I get why you did it like this. It's just that the end effect
is to make --include-barrier seem less disparaged than the other
--include-* options, but I'm not sure there's supposed to be any
difference between them in that respect.
Perhaps we should drop the "Use the latter option instead." thing
altogether for aliases. I'm not sure that it really helps, and this
thread shows that adding it automatically can lead to some odd corner
cases.
In practice we shouldn't remove any of these aliases unless we're
also removing the option that they're an alias of. And if we do that,
the options should go through the usual deprecation cycle, just like
options without aliases.
If there are specific options that we want to steer users away
from without deprecation, then we should probably have a specific
tag for that.
The "Use the latter option" text was the outcome of the discussion
of the patch for PR 68043:
https://gcc.gnu.org/legacy-ml/gcc-patches/2015-10/msg01395.html
where Joseph wanted to steer users toward the alternatives. I
don't feel too strongly about it but reviewing the thread might
be helpful.
Thanks for the pointer. But I think Joseph's comment was more about
not reproducing the documentation of the alias target:
I also think it would be better just to give the "Same as" message
without also repeating the description of the canonical option.
on the basis that:
Well, I think it might also encourage people to use the aliases, when
for the most part we'd rather people used the canonical names (and so
made it easier e.g. to search for other uses of the same option).
And Lewis's patch is still doing that. It doesn't look like there was
a specific request to add extra text to steer the user away from the alias.
I can understand why adding that text seemed like a good idea,
but I think Lewis's patch shows that it can also produce some oddities.
IMO we should stick to what we know is correct: that the option is an
alias of some other option.
Sure. I have no objection. I just wanted to give some background
on why the code is the way it is.
FWIW, I expect the majority or users, especially those looking for
help with options, will refer to the more verbose text in the manual
far more often than to the --help output. I think any guidance we
give will be more effective in the former.
Martin
FWIW, an enhancement to consider is making use of colors in
the output (under the same conditions as in diagnostics). That
would make it possible to differentiate between recommended
options and their discouraged or deprecated counterparts (among
other things).
Yeah, sounds like it could be useful.
Thanks,
Richard
