Description
Description
perldoc -f open:
As a special case the three-argument form with a read/write mode and the third argument being
undef:open(my $tmp, "+>", undef) or die ...opens a filehandle to a newly created empty anonymous temporary file. (This happens under any mode, which makes
+>the only useful and sensible mode to use.) You will need toseekto do the reading.
This feature was added in 5.8.0 and is intended to only trigger when a literal undef is passed as the filename. It does not happen if a variable whose contents are undef is used:
$ perl -we 'open(my $fh, "+>", my $bogus) or die $!'
Use of uninitialized value $bogus in open at -e line 1.
No such file or directory at -e line 1.
$ perl -we 'my @bogus = undef; open(my $fh, "+>", $bogus[0]) or die $!'
Use of uninitialized value $bogus[0] in open at -e line 1.
No such file or directory at -e line 1.
$ perl -we 'my %bogus = (a => undef); open(my $fh, "+>", $bogus{a}) or die $!'
Use of uninitialized value $bogus{"a"} in open at -e line 1.
No such file or directory at -e line 1.
Steps to Reproduce
However, if you use an array or hash element that doesn't exist at all (as opposed to existing but containing undef), the special behavior kicks in and open silently succeeds, creating a temp file:
$ perl -we 'my @bogus; open(my $fh, "+>", $bogus[0]) or die $!'
$ perl -we 'my %bogus; open(my $fh, "+>", $bogus{a}) or die $!'
$ perl -we 'open(my $fh, "+>", $ARGV[0]) or die $!'
$
Even this behavior is not entirely consistent, however. If you use a runtime call to &CORE::open, it starts failing again (but with duplicate warning messages for some reason):
$ perl -we 'my @bogus; &CORE::open(my $fh, "+>", $bogus[0]) or die $!'
Use of uninitialized value in open at -e line 1.
Use of uninitialized value in open at -e line 1.
No such file or directory at -e line 1.
$ perl -we 'my %bogus; &CORE::open(my $fh, "+>", $bogus{a}) or die $!'
Use of uninitialized value in open at -e line 1.
Use of uninitialized value in open at -e line 1.
No such file or directory at -e line 1.
Expected behavior
A call to open that does not pass a literal undef, but an element of an array or hash, should complain about the undefined value and fail. Basically like the &CORE::open version, but there I'd expect to see only one copy of the warning.
Perl configuration
Summary of my perl5 (revision 5 version 40 subversion 0) configuration:
Platform:
osname=linux
osvers=6.5.0-10040-tuxedo
archname=x86_64-linux-thread-multi-ld
uname='linux luum 6.5.0-10040-tuxedo #44 smp preempt_dynamic wed may 8 17:36:39 utc 2024 x86_64 x86_64 x86_64 gnulinux '
config_args='-de -Dprefix=/home/mauke/perl5/perlbrew/perls/perl-5.40.0 -Dcc=cgcc -Dman1dir=none -Dman3dir=none -Dusethreads -Duselongdouble -Aoptimize=-flto -Aeval:scriptdir=/home/mauke/perl5/perlbrew/perls/perl-5.40.0/bin'
hint=recommended
useposix=true
d_sigaction=define
useithreads=define
usemultiplicity=define
use64bitint=define
use64bitall=define
uselongdouble=define
usemymalloc=n
default_inc_excludes_dot=define
Compiler:
cc='cgcc'
ccflags ='-D_REENTRANT -D_GNU_SOURCE -fwrapv -fno-strict-aliasing -pipe -fstack-protector-strong -I/usr/local/include -D_LARGEFILE_SOURCE -D_FILE_OFFSET_BITS=64'
optimize='-O2 -flto'
cppflags='-D_REENTRANT -D_GNU_SOURCE -fwrapv -fno-strict-aliasing -pipe -fstack-protector-strong -I/usr/local/include'
ccversion=''
gccversion='11.4.0'
gccosandvers=''
intsize=4
longsize=8
ptrsize=8
doublesize=8
byteorder=12345678
doublekind=3
d_longlong=define
longlongsize=8
d_longdbl=define
longdblsize=16
longdblkind=3
ivtype='long'
ivsize=8
nvtype='long double'
nvsize=16
Off_t='off_t'
lseeksize=8
alignbytes=16
prototype=define
Linker and Libraries:
ld='cgcc'
ldflags =' -fstack-protector-strong -L/usr/local/lib'
libpth=/usr/local/lib /usr/lib/x86_64-linux-gnu /usr/lib /usr/lib64
libs=-lpthread -ldb -ldl -lm -lcrypt -lutil -lc
perllibs=-lpthread -ldl -lm -lcrypt -lutil -lc
libc=/lib/x86_64-linux-gnu/libc.so.6
so=so
useshrplib=false
libperl=libperl.a
gnulibc_version='2.35'
Dynamic Linking:
dlsrc=dl_dlopen.xs
dlext=so
d_dlsymun=undef
ccdlflags='-Wl,-E'
cccdlflags='-fPIC'
lddlflags='-shared -O2 -flto -L/usr/local/lib -fstack-protector-strong'
Characteristics of this binary (from libperl):
Compile-time options:
HAS_LONG_DOUBLE
HAS_STRTOLD
HAS_TIMES
MULTIPLICITY
PERLIO_LAYERS
PERL_COPY_ON_WRITE
PERL_DONT_CREATE_GVSV
PERL_HASH_FUNC_SIPHASH13
PERL_HASH_USE_SBOX32
PERL_MALLOC_WRAP
PERL_OP_PARENT
PERL_PRESERVE_IVUV
PERL_USE_SAFE_PUTENV
USE_64_BIT_ALL
USE_64_BIT_INT
USE_ITHREADS
USE_LARGE_FILES
USE_LOCALE
USE_LOCALE_COLLATE
USE_LOCALE_CTYPE
USE_LOCALE_NUMERIC
USE_LOCALE_TIME
USE_LONG_DOUBLE
USE_PERLIO
USE_PERL_ATOF
USE_REENTRANT_API
USE_THREAD_SAFE_LOCALE
Built under linux
Compiled at Jun 9 2024 23:04:17
%ENV:
PERLBREW_BASHRC_VERSION="0.74"
PERLBREW_HOME="/home/mauke/.perlbrew"
PERLBREW_MANPATH="/home/mauke/perl5/perlbrew/perls/perl-5.40.0/man"
PERLBREW_PATH="/home/mauke/perl5/perlbrew/bin:/home/mauke/perl5/perlbrew/perls/perl-5.40.0/bin"
PERLBREW_PERL="perl-5.40.0"
PERLBREW_ROOT="/home/mauke/perl5/perlbrew"
PERLBREW_VERSION="0.94"
PERLDOC="-oman"
PERL_UNICODE="SAL"
@INC:
/home/mauke/perl5/perlbrew/perls/perl-5.40.0/lib/site_perl/5.40.0/x86_64-linux-thread-multi-ld
/home/mauke/perl5/perlbrew/perls/perl-5.40.0/lib/site_perl/5.40.0
/home/mauke/perl5/perlbrew/perls/perl-5.40.0/lib/5.40.0/x86_64-linux-thread-multi-ld
/home/mauke/perl5/perlbrew/perls/perl-5.40.0/lib/5.40.0