perl5004delta.pod

ARM上的如果你对底层感兴趣

=item Applying %s to %s will act on scalar(%s)

(W) The pattern match (//), substitution (s///), and transliteration (tr///)
operators work on scalar values.  If you apply one of them to an array
or a hash, it will convert the array or hash to a scalar value -- the
length of an array, or the population info of a hash -- and then work on
that scalar value.  This is probably not what you meant to do.  See
L<perlfunc/grep> and L<perlfunc/map> for alternatives.

=item Attempt to free nonexistent shared string

(P) Perl maintains a reference counted internal table of strings to
optimize the storage and access of hash keys and other strings.  This
indicates someone tried to decrement the reference count of a string
that can no longer be found in the table.

=item Attempt to use reference as lvalue in substr

(W) You supplied a reference as the first argument to substr() used
as an lvalue, which is pretty strange.  Perhaps you forgot to
dereference it first.  See L<perlfunc/substr>.

=item Bareword "%s" refers to nonexistent package

(W) You used a qualified bareword of the form C<Foo::>, but
the compiler saw no other uses of that namespace before that point.
Perhaps you need to predeclare a package?

=item Can't redefine active sort subroutine %s

(F) Perl optimizes the internal handling of sort subroutines and keeps
pointers into them.  You tried to redefine one such sort subroutine when it
was currently active, which is not allowed.  If you really want to do
this, you should write C<sort { &func } @x> instead of C<sort func @x>.

=item Can't use bareword ("%s") as %s ref while "strict refs" in use

(F) Only hard references are allowed by "strict refs".  Symbolic references
are disallowed.  See L<perlref>.

=item Cannot resolve method `%s' overloading `%s' in package `%s'

(P) Internal error trying to resolve overloading specified by a method
name (as opposed to a subroutine reference).

=item Constant subroutine %s redefined

(S) You redefined a subroutine which had previously been eligible for
inlining.  See L<perlsub/"Constant Functions"> for commentary and
workarounds.

=item Constant subroutine %s undefined

(S) You undefined a subroutine which had previously been eligible for
inlining.  See L<perlsub/"Constant Functions"> for commentary and
workarounds.

=item Copy method did not return a reference

(F) The method which overloads "=" is buggy. See L<overload/Copy Constructor>.

=item Died

(F) You passed die() an empty string (the equivalent of C<die "">) or
you called it with no args and both C<$@> and C<$_> were empty.

=item Exiting pseudo-block via %s

(W) You are exiting a rather special block construct (like a sort block or
subroutine) by unconventional means, such as a goto, or a loop control
statement.  See L<perlfunc/sort>.

=item Identifier too long

(F) Perl limits identifiers (names for variables, functions, etc.) to
252 characters for simple names, somewhat more for compound names (like
C<$A::B>).  You've exceeded Perl's limits.  Future versions of Perl are
likely to eliminate these arbitrary limitations.

=item Illegal character %s (carriage return)

(F) A carriage return character was found in the input.  This is an
error, and not a warning, because carriage return characters can break
multi-line strings, including here documents (e.g., C<print E<lt>E<lt>EOF;>).

=item Illegal switch in PERL5OPT: %s

(X) The PERL5OPT environment variable may only be used to set the
following switches: B<-[DIMUdmw]>.

=item Integer overflow in hex number

(S) The literal hex number you have specified is too big for your
architecture. On a 32-bit architecture the largest hex literal is
0xFFFFFFFF.

=item Integer overflow in octal number

(S) The literal octal number you have specified is too big for your
architecture. On a 32-bit architecture the largest octal literal is
037777777777.

=item internal error: glob failed

(P) Something went wrong with the external program(s) used for C<glob>
and C<E<lt>*.cE<gt>>.  This may mean that your csh (C shell) is
broken.  If so, you should change all of the csh-related variables in
config.sh:  If you have tcsh, make the variables refer to it as if it
were csh (e.g. C<full_csh='/usr/bin/tcsh'>); otherwise, make them all
empty (except that C<d_csh> should be C<'undef'>) so that Perl will
think csh is missing.  In either case, after editing config.sh, run
C<./Configure -S> and rebuild Perl.

=item Invalid conversion in %s: "%s"

(W) Perl does not understand the given format conversion.
See L<perlfunc/sprintf>.

=item Invalid type in pack: '%s'

(F) The given character is not a valid pack type.  See L<perlfunc/pack>.

=item Invalid type in unpack: '%s'

(F) The given character is not a valid unpack type.  See L<perlfunc/unpack>.

=item Name "%s::%s" used only once: possible typo

(W) Typographical errors often show up as unique variable names.
If you had a good reason for having a unique name, then just mention
it again somehow to suppress the message (the C<use vars> pragma is
provided for just this purpose).

=item Null picture in formline

(F) The first argument to formline must be a valid format picture
specification.  It was found to be empty, which probably means you
supplied it an uninitialized value.  See L<perlform>.

=item Offset outside string

(F) You tried to do a read/write/send/recv operation with an offset
pointing outside the buffer.  This is difficult to imagine.
The sole exception to this is that C<sysread()>ing past the buffer
will extend the buffer and zero pad the new area.

=item Out of memory!

(X|F) The malloc() function returned 0, indicating there was insufficient
remaining memory (or virtual memory) to satisfy the request.

The request was judged to be small, so the possibility to trap it
depends on the way Perl was compiled.  By default it is not trappable.
However, if compiled for this, Perl may use the contents of C<$^M> as
an emergency pool after die()ing with this message.  In this case the
error is trappable I<once>.

=item Out of memory during request for %s

(F) The malloc() function returned 0, indicating there was insufficient
remaining memory (or virtual memory) to satisfy the request. However,
the request was judged large enough (compile-time default is 64K), so
a possibility to shut down by trapping this error is granted.

=item panic: frexp

(P) The library function frexp() failed, making printf("%f") impossible.

=item Possible attempt to put comments in qw() list

(W) qw() lists contain items separated by whitespace; as with literal
strings, comment characters are not ignored, but are instead treated
as literal data.  (You may have used different delimiters than the
parentheses shown here; braces are also frequently used.)

You probably wrote something like this:

    @list = qw(
        a # a comment
        b # another comment
    );

when you should have written this:

    @list = qw(
        a
        b
    );

If you really want comments, build your list the
old-fashioned way, with quotes and commas:

    @list = (
        'a',    # a comment
        'b',    # another comment
    );

=item Possible attempt to separate words with commas

(W) qw() lists contain items separated by whitespace; therefore commas
aren't needed to separate the items. (You may have used different
delimiters than the parentheses shown here; braces are also frequently
used.)

You probably wrote something like this:

    qw! a, b, c !;

which puts literal commas into some of the list items.  Write it without
commas if you don't want them to appear in your data:

    qw! a b c !;

=item Scalar value @%s{%s} better written as $%s{%s}

(W) You've used a hash slice (indicated by @) to select a single element of
a hash.  Generally it's better to ask for a scalar value (indicated by $).
The difference is that C<$foo{&bar}> always behaves like a scalar, both when
assigning to it and when evaluating its argument, while C<@foo{&bar}> behaves
like a list when you assign to it, and provides a list context to its
subscript, which can do weird things if you're expecting only one subscript.

=item Stub found while resolving method `%s' overloading `%s' in package `%s'

(P) Overloading resolution over @ISA tree may be broken by importing stubs.
Stubs should never be implicitely created, but explicit calls to C<can>
may break this.

=item Too late for "B<-T>" option

(X) The #! line (or local equivalent) in a Perl script contains the
B<-T> option, but Perl was not invoked with B<-T> in its argument
list.  This is an error because, by the time Perl discovers a B<-T> in
a script, it's too late to properly taint everything from the
environment.  So Perl gives up.

=item untie attempted while %d inner references still exist

(W) A copy of the object returned from C<tie> (or C<tied>) was still
valid when C<untie> was called.

=item Unrecognized character %s

(F) The Perl parser has no idea what to do with the specified character
in your Perl script (or eval).  Perhaps you tried to run a compressed
script, a binary program, or a directory as a Perl program.

=item Unsupported function fork

(F) Your version of executable does not support forking.

Note that under some systems, like OS/2, there may be different flavors of
Perl executables, some of which may support fork, some not. Try changing
the name you call Perl by to C<perl_>, C<perl__>, and so on.

=item Use of "$$<digit>" to mean "${$}<digit>" is deprecated

(D) Perl versions before 5.004 misinterpreted any type marker followed
by "$" and a digit.  For example, "$$0" was incorrectly taken to mean
"${$}0" instead of "${$0}".  This bug is (mostly) fixed in Perl 5.004.

However, the developers of Perl 5.004 could not fix this bug completely,
because at least two widely-used modules depend on the old meaning of
"$$0" in a string.  So Perl 5.004 still interprets "$$<digit>" in the
old (broken) way inside strings; but it generates this message as a
warning.  And in Perl 5.005, this special treatment will cease.

=item Value of %s can be "0"; test with defined()

(W) In a conditional expression, you used <HANDLE>, <*> (glob), C<each()>,
or C<readdir()> as a boolean value.  Each of these constructs can return a
value of "0"; that would make the conditional expression false, which is
probably not what you intended.  When using these constructs in conditional
expressions, test their values with the C<defined> operator.

=item Variable "%s" may be unavailable

(W) An inner (nested) I<anonymous> subroutine is inside a I<named>
subroutine, and outside that is another subroutine; and the anonymous
(innermost) subroutine is referencing a lexical variable defined in
the outermost subroutine.  For example:

   sub outermost { my $a; sub middle { sub { $a } } }

If the anonymous subroutine is called or referenced (directly or
indirectly) from the outermost subroutine, it will share the variable
as you would expect.  But if the anonymous subroutine is called or
referenced when the outermost subroutine is not active, it will see
the value of the shared variable as it was before and during the
*first* call to the outermost subroutine, which is probably not what
you want.

In these circumstances, it is usually best to make the middle
subroutine anonymous, using the C<sub {}> syntax.  Perl has specific
support for shared variables in nested anonymous subroutines; a named
subroutine in between interferes with this feature.

=item Variable "%s" will not stay shared

(W) An inner (nested) I<named> subroutine is referencing a lexical
variable defined in an outer subroutine.

When the inner subroutine is called, it will probably see the value of
the outer subroutine's variable as it was before and during the
*first* call to the outer subroutine; in this case, after the first
call to the outer subroutine is complete, the inner and outer
subroutines will no longer share a common value for the variable.  In
other words, the variable will no longer be shared.

Furthermore, if the outer subroutine is anonymous and references a
lexical variable outside itself, then the outer and inner subroutines
will I<never> share the given variable.

This problem can usually be solved by making the inner subroutine
anonymous, using the C<sub {}> syntax.  When inner anonymous subs that
reference variables in outer subroutines are called or referenced,
they are automatically rebound to the current values of such
variables.

=item Warning: something's wrong

(W) You passed warn() an empty string (the equivalent of C<warn "">) or
you called it with no args and C<$_> was empty.

=item Ill-formed logical name |%s| in prime_env_iter

(W) A warning peculiar to VMS.  A logical name was encountered when preparing
to iterate over %ENV which violates the syntactic rules governing logical
names.  Since it cannot be translated normally, it is skipped, and will not
appear in %ENV.  This may be a benign occurrence, as some software packages
might directly modify logical name tables and introduce nonstandard names,
or it may indicate that a logical name table has been corrupted.

=item Got an error from DosAllocMem

(P) An error peculiar to OS/2.  Most probably you're using an obsolete
version of Perl, and this should not happen anyway.

=item Malformed PERLLIB_PREFIX

(F) An error peculiar to OS/2.  PERLLIB_PREFIX should be of the form

    prefix1;prefix2

or

    prefix1 prefix2

with nonempty prefix1 and prefix2.  If C<prefix1> is indeed a prefix
of a builtin library search path, prefix2 is substituted.  The error
may appear if components are not found, or are too long.  See
"PERLLIB_PREFIX" in F<README.os2>.

=item PERL_SH_DIR too long

(F) An error peculiar to OS/2. PERL_SH_DIR is the directory to find the
C<sh>-shell in.  See "PERL_SH_DIR" in F<README.os2>.

=item Process terminated by SIG%s

(W) This is a standard message issued by OS/2 applications, while *nix
applications die in silence.  It is considered a feature of the OS/2
port.  One can easily disable this by appropriate sighandlers, see
L<perlipc/"Signals">.  See also "Process terminated by SIGTERM/SIGINT"
in F<README.os2>.

=back

=head1 BUGS

If you find what you think is a bug, you might check the headers of
recently posted articles in the comp.lang.perl.misc newsgroup.
There may also be information at http://www.perl.com/perl/, the Perl
Home Page.

If you believe you have an unreported bug, please run the B<perlbug>
program included with your release.  Make sure you trim your bug down
to a tiny but sufficient test case.  Your bug report, along with the
output of C<perl -V>, will be sent off to <F<[e-mail]>> to be
analysed by the Perl porting team.

=head1 SEE ALSO

The F<Changes> file for exhaustive details on what changed.

The F<INSTALL> file for how to build Perl.  This file has been
significantly updated for 5.004, so even veteran users should
look through it.

The F<README> file for general stuff.

The F<Copying> file for copyright information.

=head1 HISTORY

Constructed by Tom Christiansen, grabbing material with permission
from innumerable contributors, with kibitzing by more than a few Perl
porters.

Last update: Wed May 14 11:14:09 EDT 1997