"Keyword" labels now forbidden (was [perl.git] branch blead, updated. GitLive-blead-1705-gf71d615)
Jerry D. Hedden
>
> <http://perl5.git.perl.org/perl.git/commitdiff/f71d6157c7933c0d3df645f0411d97d7e2b66b2f?hp=0409250f9c9eac87ff80d18e21856800e91763b5>
>
> - Log -----------------------------------------------------------------
> commit f71d6157c7933c0d3df645f0411d97d7e2b66b2f
> Author: Rafael Garcia-Suarez <rgarci...@gmail.com>
> Date: Tue Jul 28 09:47:24 2009 +0200
>
> Forbid labels with keyword names
Interesting. This "broke" one of my CPAN modules. Wonder how many
others it will affect?
David Nicol
>
> Interesting. This "broke" one of my CPAN modules. Wonder how many
> others it will affect?
Why? I've always considered the fact that you can generally use
keywords as other things in Perl to be a good thing.
$ perl -le 'goto: $x++ > 3 and die 1; print $x; goto goto'
1
goto must have label at -e line 1.
$ perl -le 'goto: $x++ > 3 and die 1; print $x; goto "goto"'
1
2
3
4
1 at -e line 1.
it's already a synbtax error when it makes no sense. What's the harm?
--
"It wasn't worth it." -- Harry Patch
Rafael Garcia-Suarez
I guess that only demonstrates that one can never underestimate the
importance of backwards compatibility. I would never have guessed I
had such a report that fast.
What was the code you used ?
Rafael Garcia-Suarez
>>> Forbid labels with keyword names
>>
>> Interesting. This "broke" one of my CPAN modules. Wonder how many
>> others it will affect?
>
>
> Why? I've always considered the fact that you can generally use
> keywords as other things in Perl to be a good thing.
>
> $ perl -le 'goto: $x++ > 3 and die 1; print $x; goto goto'
> 1
> goto must have label at -e line 1.
This error is about the second goto.
> $ perl -le 'goto: $x++ > 3 and die 1; print $x; goto "goto"'
> 1
> 2
> 3
> 4
> 1 at -e line 1.
>
> it's already a synbtax error when it makes no sense. What's the harm?
No it's not :
$ perl -e 'goto print'
Can't find label 1 at -e line 1.
David Nicol
Garcia-Suarez<rgarci...@gmail.com> wrote:
> 2009/7/30 David Nicol <david...@gmail.com>:
>> it's already a synbtax error when it makes no sense. What's the harm?
>
> No it's not :
>
> $ perl -e 'goto print'
> Can't find label 1 at -e line 1.
$ perl -le '1: $x++ > 3 and die 1; goto print $x'
syntax error at -e line 1, near "1:"
Execution of -e aborted due to compilation errors.
is there a way to create "1" as a label? perldoc perlsyn says labels
"consist of an identifer followed by a colon" but the word
"identifier" does not appear again in that document.
Allowing numeric labels would make Perl more friendly to FORTRAN programmers...
Rafael Garcia-Suarez
Or BASIC.
At best I could write a source filter for that. Colon-less numeric
labels at the beginning of lines. And allow uppercase GOTO.
10 say "this is perl, sort of\n";
20 GOTO 10;
Jerry D. Hedden
>
> <http://perl5.git.perl.org/perl.git/commitdiff/f71d6157c7933c0d3df645f0411d97d7e2b66b2f?hp=0409250f9c9eac87ff80d18e21856800e91763b5>
>
> - Log -----------------------------------------------------------------
> commit f71d6157c7933c0d3df645f0411d97d7e2b66b2f
> Author: Rafael Garcia-Suarez <rgarci...@gmail.com>
> Date: Tue Jul 28 09:47:24 2009 +0200
>
> Forbid labels with keyword names
Jerry D. Hedden wrote:
>> Interesting. This "broke" one of my CPAN modules. Wonder how many
>> others it will affect?
Rafael Garcia-Suarez wrote:
> I guess that only demonstrates that one can never underestimate the
> importance of backwards compatibility. I would never have guessed I
> had such a report that fast.
>
> What was the code you used ?
The construct was something like this:
# Check on what we've found
CHECK:
foreach my $key (keys(%{$spec})) {
my $spec_item = $$spec{$key};
# No specs to check
if (ref($spec_item) ne 'HASH') {
# The specifier entry was just 'key => regex'. If 'key' is not in
# the args, the we need to remove the 'undef' entry in the found
# args hash.
if (! defined($found{$key})) {
delete($found{$key});
}
next CHECK;
}
... and more similar check ...
}
I didn't think of the label as a keyword. I changed it to
CHECKIT to fix the problem.
I don't have a problem with the change itself. I think it's
a good idea. However, the error message you get doesn't
tell you what you did wrong! Consider:
#!/usr/bin/perl
use strict;
use warnings;
CHECK:
foreach (1..3) {
if ($_ == 2) {
next CHECK;
}
}
# EOF
When run, this produces:
syntax error at label.pl line 7, near ":
foreach "
Execution of label.pl aborted due to compilation errors.
It was only because I had just seen this change to blead
that I understood what the errors I was getting were related
to. Otherwise, I would have been scratching my head, and
probably asking for help on perl5-porters.
How about an error message that tells what the problem
really is:
Can't use keyword as a label.
Otherwise, it may become a problem when this change hits the
streets.
Jerry D. Hedden
> I suspect that you wont be the only one who get nailed by this. I
> suspect that INIT/CHECK are both likely to be common as labels (in
> sofar as labels go).
Precisely why I wrote about it - just to give people a heads-up.
However, the error message needs to be changed to say that using
a keyword as a label is not allowed.
Demerphq
I suspect that you wont be the only one who get nailed by this. I
suspect that INIT/CHECK are both likely to be common as labels (in
sofar as labels go).
Yves
--
perl -Mre=debug -e "/just|another|perl|hacker/"
David E. Wheeler
> First, how about if we disallow only the BEGIN-family of keywords as
> labels?
> Considering the original bug report those are the ones that can cause
> trouble. Writing "for: {}" is weird but why should we stop you,
> really?
I think just disallowing the uppercase keywords would be sufficient.
> Second, how about if any limitations on labels is only if they're to
> blocks?
> There's no possible confusion about the meaning of the label in:
>
> sub foo () {
> CHECK: for (@a) { ... }
> }
>
> so I don't think we need to forbid it.
Yeah, but then it's inconsistent. Sometimes you can use CHECK for a
label and sometimes you can't?
Best,
David
Nicholas Clark
> On Jul 30, 2009, at 10:27 AM, Chip Salzenberg wrote:
>
> >First, how about if we disallow only the BEGIN-family of keywords as
> >labels?
> >Considering the original bug report those are the ones that can cause
> >trouble. Writing "for: {}" is weird but why should we stop you,
> >really?
>
> I think just disallowing the uppercase keywords would be sufficient.
Except that the problem is the keywords that are functions:
$ perl -e 'print: goto print'
Can't find label 1 at -e line 1.
Nicholas Clark
Rafael Garcia-Suarez
> the sanest option. Fortunately we do have C<use VERSION> to limit any
> collateral damage from new keywords.
Yes, that's what seemed to me too.
I've now checked in an error message improvement as suggested by Jerry.
$ bleadperl -Esay:
Can't use keyword 'say' as a label at -e line 1.
You will note that "bleadperl -esay:" doesn't produce an error. Only
current keywords are checked.