Perl needs an Errno.pm for h_errno

[p5pRT]

Migrated from rt.perl.org#66804 (status was 'open')

Searchable as RT66804$

[p5pRT]

From tlhackque@yahoo.com

Created by tlhackque@yahoo.com

The gethost* (e.g. gethostbyaddr) functions document that "if h_errno
is supported by C, h_errno is returned in $? if a call fails." This is
repeated in the documentation for $?.

I would like to ascribe meaning to the returned value. But I have been
unable to find symbolic values (e.g. from C's netdb.h) such as TRY_AGAIN
and HOST_NOT_FOUND defined in Perl. Nor a hstrerror() equivalent.

This makes it rather difficult to write portable scripts that check for
and report netdb errors for humans.

There is some discussion of this in​:
  http​://www.perlmonks.org/index.pl?node_id=773351
The suggestion there is to extract the values (in a very fragile manner)
from netdb.h at runtime.

I believe that this belongs in the core - either as an extension to
Error.pm or as a parallel mechanism.

Please consider adding this support. (Or, if I've missed an existing
capability, I'd appreciate a pointer. And the documentation for the
gethost* functions & $? should get that pointer as well!)

Thanks.

Perl Info

Flags:
    category=core
    severity=medium

This perlbug was built using Perl v5.8.8 in the Red Hat build system.
It is being executed now by Perl v5.8.8 - Mon Nov 12 21:35:26 EST 2007.

Site configuration information for perl v5.8.8:

Configured by Red Hat, Inc. at Mon Nov 12 21:35:26 EST 2007.

Summary of my perl5 (revision 5 version 8 subversion 8) configuration:
  Platform:
    osname=linux, osvers=2.6.9-55.0.9.elsmp, archname=i386-linux-thread-multi
    uname='linux hs20-bc2-2.build.redhat.com 2.6.9-55.0.9.elsmp #1 smp tue sep 25 02:16:15 edt 2007 i686 i686 i386 gnulinux '
    config_args='-des -Doptimize=-O2 -g -pipe -Wall -Wp,-D_FORTIFY_SOURCE=2 -fexceptions -fstack-protector --param=ssp-buffer-size=4 -m32 -march=i386 -mtune=generic -fasynchronous-unwind-tables -Dversion=5.8.8 -Dmyhostname=localhost -Dperladmin=root@localhost -Dcc=gcc -Dcf_by=Red Hat, Inc. -Dinstallprefix=/usr -Dprefix=/usr -Darchname=i386-linux -Dvendorprefix=/usr -Dsiteprefix=/usr -Duseshrplib -Dusethreads -Duseithreads -Duselargefiles -Dd_dosuid -Dd_semctl_semun -Di_db -Ui_ndbm -Di_gdbm -Di_shadow -Di_syslog -Dman3ext=3pm -Duseperlio -Dinstallusrbinperl=n -Ubincompat5005 -Uversiononly -Dpager=/usr/bin/less -isr -Dd_gethostent_r_proto -Ud_endhostent_r_proto -Ud_sethostent_r_proto -Ud_endprotoent_r_proto -Ud_setprotoent_r_proto -Ud_endservent_r_proto -Ud_setservent_r_proto -Dinc_version_list=5.8.7 5.8.6 5.8.5 -Dscriptdir=/usr/bin'
    hint=recommended, useposix=true, d_sigaction=define
    usethreads=define use5005threads=undef useithreads=define usemultiplicity=define
    useperlio=define d_sfio=undef uselargefiles=define usesocks=undef
    use64bitint=undef use64bitall=undef uselongdouble=undef
    usemymalloc=n, bincompat5005=undef
  Compiler:
    cc='gcc', ccflags ='-D_REENTRANT -D_GNU_SOURCE -fno-strict-aliasing -pipe -Wdeclaration-after-statement -I/usr/local/include -D_LARGEFILE_SOURCE -D_FILE_OFFSET_BITS=64 -I/usr/include/gdbm',
    optimize='-O2 -g -pipe -Wall -Wp,-D_FORTIFY_SOURCE=2 -fexceptions -fstack-protector --param=ssp-buffer-size=4 -m32 -march=i386 -mtune=generic -fasynchronous-unwind-tables',
    cppflags='-D_REENTRANT -D_GNU_SOURCE -fno-strict-aliasing -pipe -Wdeclaration-after-statement -I/usr/local/include -I/usr/include/gdbm'
    ccversion='', gccversion='4.1.2 20070626 (Red Hat 4.1.2-13)', gccosandvers=''
    intsize=4, longsize=4, ptrsize=4, doublesize=8, byteorder=1234
    d_longlong=define, longlongsize=8, d_longdbl=define, longdblsize=12
    ivtype='long', ivsize=4, nvtype='double', nvsize=8, Off_t='off_t', lseeksize=8
    alignbytes=4, prototype=define
  Linker and Libraries:
    ld='gcc', ldflags =' -L/usr/local/lib'
    libpth=/usr/local/lib /lib /usr/lib
    libs=-lresolv -lnsl -lgdbm -ldb -ldl -lm -lcrypt -lutil -lpthread -lc
    perllibs=-lresolv -lnsl -ldl -lm -lcrypt -lutil -lpthread -lc
    libc=/lib/libc-2.5.so, so=so, useshrplib=true, libperl=libperl.so
    gnulibc_version='2.5'
  Dynamic Linking:
    dlsrc=dl_dlopen.xs, dlext=so, d_dlsymun=undef, ccdlflags='-Wl,-E -Wl,-rpath,/usr/lib/perl5/5.8.8/i386-linux-thread-multi/CORE'
    cccdlflags='-fPIC', lddlflags='-shared -O2 -g -pipe -Wall -Wp,-D_FORTIFY_SOURCE=2 -fexceptions -fstack-protector --param=ssp-buffer-size=4 -m32 -march=i386 -mtune=generic -fasynchronous-unwind-tables -L/usr/local/lib'

Locally applied patches:
    


@INC for perl v5.8.8:
    /usr/lib/perl5/site_perl/5.8.8/i386-linux-thread-multi
    /usr/lib/perl5/site_perl/5.8.7/i386-linux-thread-multi
    /usr/lib/perl5/site_perl/5.8.6/i386-linux-thread-multi
    /usr/lib/perl5/site_perl/5.8.5/i386-linux-thread-multi
    /usr/lib/perl5/site_perl/5.8.8
    /usr/lib/perl5/site_perl/5.8.7
    /usr/lib/perl5/site_perl/5.8.6
    /usr/lib/perl5/site_perl/5.8.5
    /usr/lib/perl5/site_perl
    /usr/lib/perl5/vendor_perl/5.8.8/i386-linux-thread-multi
    /usr/lib/perl5/vendor_perl/5.8.7/i386-linux-thread-multi
    /usr/lib/perl5/vendor_perl/5.8.6/i386-linux-thread-multi
    /usr/lib/perl5/vendor_perl/5.8.5/i386-linux-thread-multi
    /usr/lib/perl5/vendor_perl/5.8.8
    /usr/lib/perl5/vendor_perl/5.8.7
    /usr/lib/perl5/vendor_perl/5.8.6
    /usr/lib/perl5/vendor_perl/5.8.5
    /usr/lib/perl5/vendor_perl
    /usr/lib/perl5/5.8.8/i386-linux-thread-multi
    /usr/lib/perl5/5.8.8
    .


Environment for perl v5.8.8:
    HOME=/root
    LANG=en_US.UTF-8
    LANGUAGE (unset)
    LD_LIBRARY_PATH (unset)
    LOGDIR (unset)
    PATH=/usr/kerberos/sbin:/usr/kerberos/bin:/usr/lib/ccache:/usr/local/bin:/bin:/usr/bin:/home/litt/www/./../bin
    PERL_BADLANG (unset)
    SHELL=/bin/bash

[p5pRT]

From tlhackque@yahoo.com

Here is my interim solution - perhaps it will inspire someone to do it
right.

'Right' means that the database should be built at configure time, like
Errno.pm & that the list of symbols should come from the system, not be
built-in to the .pm. And it should be distributed with the core.

Nonetheless, this interim solution is probably quite usable for many
environments...

Enjoy.

[p5pRT]

From tlhackque@yahoo.com

Herrno.pm

[p5pRT]

tlhackque@yahoo.com - Status changed from 'new' to 'open'

[p5pRT]

From @rgs

2009/6/21 via RT <perlbug-followup@​perl.org>​:

The gethost* (e.g. gethostbyaddr) functions document that "if h_errno
is supported by C, h_errno is returned in $? if a call fails."  This is
repeated in the documentation for $?.

I would like to ascribe meaning to the returned value.  But I have been
unable to find symbolic values (e.g. from C's netdb.h) such as TRY_AGAIN
and HOST_NOT_FOUND defined in Perl.  Nor a hstrerror() equivalent.

This makes it rather difficult to write portable scripts that check for
and report netdb errors for humans.

There is some discussion of this in​:
  http​://www.perlmonks.org/index.pl?node_id=773351
The suggestion there is to extract the values (in a very fragile manner)
from netdb.h at runtime.

I believe that this belongs in the core - either as an extension to
Error.pm or as a parallel mechanism.

Please consider adding this support.  (Or, if I've missed an existing
capability, I'd appreciate a pointer.  And the documentation for the
gethost* functions & $? should get that pointer as well!)

Those constants can probably be added to POSIX.pm.

[p5pRT]

From tlhackque@yahoo.com

It's not just the constants, but also a mechanism to turn them (portably)  into strings.
 
E.G. Errno.pm / $! is to errno as what's missing is to h_errno.  The code that I posted is one - not very elegant - approach.  It provides both constants and a means to get from the constants to strings.
 

---

This communication may not represent my employer's views,
if any, on the matters discussed.

--- On Mon, 6/22/09, Rafael Garcia-Suarez via RT <perlbug-followup@​perl.org> wrote​:

From​: Rafael Garcia-Suarez via RT <perlbug-followup@​perl.org>
Subject​: Re​: [perl #66804] Perl needs an Errno.pm for h_errno
To​: tlhackque@​yahoo.com
Date​: Monday, June 22, 2009, 11​:37 AM

2009/6/21 via RT <perlbug-followup@​perl.org>​:

The gethost* (e.g. gethostbyaddr) functions document that "if h_errno
is supported by C, h_errno is returned in $? if a call fails."  This is
repeated in the documentation for $?.

I would like to ascribe meaning to the returned value.  But I have been
unable to find symbolic values (e.g. from C's netdb.h) such as TRY_AGAIN
and HOST_NOT_FOUND defined in Perl.  Nor a hstrerror() equivalent.

This makes it rather difficult to write portable scripts that check for
and report netdb errors for humans.

There is some discussion of this in​:
  http​://www.perlmonks.org/index.pl?node_id=773351
The suggestion there is to extract the values (in a very fragile manner)
from netdb.h at runtime.

I believe that this belongs in the core - either as an extension to
Error.pm or as a parallel mechanism.

Please consider adding this support.  (Or, if I've missed an existing
capability, I'd appreciate a pointer.  And the documentation for the
gethost* functions & $? should get that pointer as well!)

Those constants can probably be added to POSIX.pm.