Front page | perl.perl5.porters |
Postings from March 2008
On Fri, Mar 21, 2008 at 12:03 PM, Abigail <abigail@abigail.be> wrote:
> Now, I'm getting confused. To me it seems you are saying that you are
> using 'local $@' inside 'foo' as to not clobber an outside $@, and then
> you're complaining that $@ isn't set when returning from 'foo'. You can't
> have it both ways.
The OP's example is too long. He wants to hide $@, but set it again in
certain circumstances, without using intermediate variables. (which will make
his code that does this not work with "older" perls if the change
would get made)
$ perl -le 'sub localdie { local $@; die "DIED\n" }; eval {
localdie(); }; print $@||"cleared\n"'
cleared
$ perl -le 'sub localdie { { local $@; }; die "DIED\n" }; eval {
localdie(); }; print $@||"cleared\n"'
DIED
Ths issue is that in the first case, the assignment to $@, which is
supposed to happen
by the eval, is affected by the local within localdie, which should
have been completed
before eval sets $@.
How can this be documented?
$ diff -u /usr/lib/perl5/5.8/pods/perlfunc.pod.orig
/usr/lib/perl5/5.8/pods/perlfunc.pod
--- /usr/lib/perl5/5.8/pods/perlfunc.pod.orig 2008-03-21
12:36:39.263371300 -0500
+++ /usr/lib/perl5/5.8/pods/perlfunc.pod 2008-03-21
12:53:19.812144700 -0500
@@ -1568,6 +1568,22 @@
particular situation, you can just use symbolic references instead, as
in case 6.
+The assignment to C<$@> occurs before restoration of localised variables,
+which means a temporary is required to mask some but not all errors:
+
+ # alter $@ on nefarious repugnancy only
+ {
+ my $e;
+ {
+ local $@; # hide outer $@
+ eval { test_repugnancy() };
+ # $@ =~ /nefarious/ and die $@; # DOES NOT WORK
+ $@ =~ /nefarious/ and $e = $@;
+ }
+ die $e if defined $e
+ }
+
+
C<eval BLOCK> does I<not> count as a loop, so the loop control statements
C<next>, C<last>, or C<redo> cannot be used to leave or restart the block.
Thread Previous
|
Thread Next