This Week on perl5-porters (21-27 April 2003)
This Week on perl5-porters (21-27 April 2003)
This week's summary presents a nice variety of language issues. Read
about some new errors, documentation patches, bug closing and
configuration.
Don't assign to %::
Dave Mitchell proposed to change assignments to %:: to be a compile-time
error (currently, this may cause crashes, and a non-warned user may fall
in this trap). Enache Adrian objected that this doesn't prevent all
nasty things that may be done with the main stash, and thus was
unnecessary bloat. Arthur Bergman proposes to mark %:: as read-only
instead. Hugo van der Sanden feels this patch is actually trying to hide
other problems.
http://xrl.us/g4o
Use of freed value in iteration
It's a well-known fact that you can crash perl by modifying an array
over which a for loop iterates. Dave Mitchell changed this into a new
fatal run-time error, Use of freed value in iteration.
http://xrl.us/g4p
Localization of lvalues
Dave Mitchell (who got bored and was browsing the bug database) reminds
the crowd that "local($x=3D'bar')" is currently equivalent to "$x=3D'bar'"
(i.e. the local() is silently ignored). This is not the right thing ; it
should either produce some error, or localize $x, before or after the
assignment occurs. The general opinion is to disallow it, purely and
simply. Rafael, noticing that other lvalues can be localized (e.g. "pos"
or "substr", although not very reliably sometimes), thinks this should
be fixed to work. Hugo, however, says that the most we can do is to add
a deprecation warning.
http://xrl.us/g4q
Slice auto-extending
But Dave didn't stop there. He also asked about whether splice() should
extend the array it operates on (bug #1832). The consensus was to fix
the docs, which are unclear.
http://xrl.us/g4r
Restricted hashes strike back
Jarkko asks for someone to solve the remaining problems about restricted
hashes -- that replace pseudohashes in the implementation of the
"fields" pragma in the perls to be released. And this someone will be
... Dave Mitchell ! (More precisely, the problem is with list assignment
to a restricted hash.) Dave sends a patch that modifies the way a
restricted hash is cleared : all keys are set to placeholders. So you
can now assign a list to a restricted hash ( %h =3D (key =3D> 1) ).
However, if this list contains a disallowed key, %h is left empty rather
than with its original contents.
http://xrl.us/g4s
Documentation effort
Casey West announces that he's going to `do something useful for
documentation', and posts a list of goals. Notably, he's willing to
coordinate and encourage efforts. Then, proving it, he posted a large
number of documentation patches, closing a large number of bugs.
http://xrl.us/g4t
Meanwhile, Nick Ing-Simmons agrees that the PerlIO / open / binmode /
perliol docs need to be cleaned up so that they fit more nicely
together.
Duplicating the DATA filehandle
Josh Purinton notices (bug #22010) that reading from a dup'ed DATA
filehandle, by doing open(F,"<&DATA"), in fact doesn't read anything.
(Further investigation indicates that this only occurs when the
environment variable PERLIO is set at "stdio".) Nick Ing-Simmons points
out that when the dup is done, the file pointer of DATA is at EOF, and
that dup'ing DATA is not going to copy the DATA buffer.
http://xrl.us/g4u
Lists in scalar context
Bug #22027 is merely a question, asked by Mike Stok : the value of $x,
after this statement :
$x =3D (1,2,3,());
is undef. Is this the right thing to do, or should the final
parentheses be ignored, hence setting $x to 3 ? Graham Barr explains
that "a list in a scalar context evaluates each element in a scalar
context before any flattening is done."
http://xrl.us/g4v
sfio
Nick Ing-Simmons asks whether sfio support can be removed. Andy
Dougherty and Stas Bekman point out that it's used on some mod_perl
installations, because under mod_perl STDOUT is tied (unless perl is
compiled to use the sfio library), and formats don't work with a tied
STDOUT. Mark Mielke considers that writing a CGI and expecting it to
work under mod_perl is naive anyway.
http://xrl.us/g4w
prebind on Mac OS X
Nathan Torkington asks about the use of the "-prebind" linker option on
Mac OS X. Dan Kogai tells him to use the update_prebinding command,
which should optimize the loading of XS modules (and other dynamic
libraries). Wilfredo S=E1nchez adds that adding "-prebind" to the linker
flags can't hurt.
http://xrl.us/g4x
etc.
Dave Mitchell fixed a case of memory corruption with the "goto &sub"
construct.
Abe Timmerman released Test-Smoke v1.17, with loads of improvements.
Peter Scott produces a mysterious case (filed as bug #21999) where $1 is
modified by an unsuccessful regex match, inside a for loop.
Several people walked through the bug database, closing bugs to be
closed, or proposing fixes for old bugs. Thanks to Robert, Ask, Arthur,
Dave, Casey, and probably others.
About this summary
This summary was brought to you by Rafael Garcia-Suarez. Weekly
summaries are available on and via a mailing
list, which subscription address is perl5-summary-subscribe@perl.org.
Feedback (and patches) welcome.
0 
rgarciasuarez
4/28/2003 8:51:31 PM
On Mon, Apr 28, 2003 at 10:51:31PM +0200, Rafael Garcia-Suarez wrote:
> Localization of lvalues
> simply. Rafael, noticing that other lvalues can be localized (e.g. "pos"
> or "substr", although not very reliably sometimes), thinks this should
> be fixed to work. Hugo, however, says that the most we can do is to add
localizing substr is always bogus, and may be even harmful somehow.
this
$x="xxx"; { local substr($x,1,1) = "y" }
localizes $x - ie. sets it to undef.
But someone may try to find the cause why $x is void elsewhere - and
letting him do so isn't fair :)
So here is my patchlet from then. A warning may be good too, until
localizing that return value will do something useful.
Regards,
Adi
----------------------------------------------------------------
--- /arc/bleadperl/op.c 2003-04-17 00:25:36.000000000 +0300
+++ bleadperl/op.c 2003-04-29 04:11:05.000000000 +0300
@@ -1141,7 +1141,7 @@ Perl_mod(pTHX_ OP *o, I32 type)
pad_free(o->op_targ);
o->op_targ = pad_alloc(o->op_type, SVs_PADMY);
assert(SvTYPE(PAD_SV(o->op_targ)) == SVt_NULL);
- if (o->op_flags & OPf_KIDS)
+ if (o->op_flags & OPf_KIDS && type)
mod(cBINOPo->op_first->op_sibling, type);
break;
0
enache
4/29/2003 3:57:08 AM
Reply:
(Thread closed)
(Thread closed)
